Perle Systems Network Router 5500072 13 User Manual
Perle P1700 series  
Bridge/Router  
Reference Manual  
All Software Versions  
Part number 5500072-13  
© Copyright 2002 by Perle Systems Ltd.  
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Introduction  
ARP—Address Resolution Protocol  
A protocol called ARP (Address Resolution Protocol) is used to determine the MAC address of a particular IP address. The  
MAC (Medium Access Control) address is unique predefined number for each device on the LAN. The manufacturer of the  
device assigns MAC addresses. The IP address for each device is assigned by the network administrator according to the  
network structure.  
If the originating station does not know the MAC address of the destination station, a MAC broadcast will be transmitted  
onto the LAN asking “Who has IP address 170.22.10.4?” This MAC broadcast is called an ARP request. Because the ARP  
request is a MAC broadcast, every device on the LAN will see the frame. The device that has the IP address 170.22.10.4 will  
respond with a frame to the originating station. The ARP reply frame will include the MAC address of the destination device.  
Now when the two devices wish to send data across the LAN to each other, they will both use the MAC and IP address of  
the other device.  
Each device on the LAN maintains a table for MAC addresses and IP addresses called the ARP cache. The ARP cache  
contains a list of IP addresses and their corresponding MAC addresses.  
Proxy ARP  
Each time an originating station does not know the MAC address of a destination station, the originating station sends out an  
ARP request. If the destination station is on a different network, the router connected to the originating network will see  
from the IP address that the frame is to be routed to another network. If the router has an entry for the destination address,  
the router will generate an ARP reply to send back to the originating station. The ARP reply will specify the MAC address of  
the router as the MAC address to send frames to for the IP address of the destination station.  
The Complete IP Connection  
The following are the steps that a frame of data will take when being transmitted from an originating station on an IP network  
to a destination station on a different IP network. In this example, the two networks are separated by a third network with  
two router hops between the originating network and the destination network.  
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Originating station will send an ARP request if it does not have the MAC address of the destination station.  
Local router will see ARP request and send an ARP reply to the originating station with the MAC address of the local  
router port.  
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Originating station will send the data frame addressed to the IP address of the destination station, and the MAC  
address of the local router port.  
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Introduction  
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Local router will receive the data frame and strip off the MAC portion. The resulting IP frame will be examined to  
determine the destination IP address.  
Local router will look in its routing table to find the IP address of the router to send the IP frame to next. The local  
router will see that the destination router is the next router.  
Local router will look in its ARP cache to find the MAC address of the destination router as determined by the IP  
address in the routing table.  
Local router will rebuild the complete frame with a new MAC header indicating the MAC address of the destination  
router. The local router does not alter the destination IP address, so the destination IP address will still be the IP  
address of the destination station.  
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•
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Destination router will receive the data frame and strip off the MAC portion. The resulting IP frame will be  
examined to determine the destination IP address.  
Destination router will look in its routing table to find the IP address of the router to send the IP frame to next. The  
destination router will see that the destination IP address is on a locally connected network.  
Destination router will look in its ARP cache to see if it has a MAC address for the destination IP address. If it does  
not have an entry, the destination router will generate an ARP request. The destination station will send an ARP  
reply.  
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•
Destination router will rebuild the complete frame with a new MAC header indicating the MAC address of the  
destination station. The destination IP address once again will be unchanged and remain as the destination station IP  
address.  
Destination station will receive the data frame and process it.  
If the destination station wishes to send a frame back to the originating station, the process will happen in the reverse  
direction.  
If the path from the originating station to the destination station causes the frame to pass through more than two routers, the  
above process will simply be extended to include the interaction between the intermediate routers.  
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Introduction  
IP Header Details  
Every IP header has common fields of information. The layout of the information is always the same. Refer to the following  
diagram for a representation of the IP header.  
Figure 1 - 2 IP Header  
Protocol  
The protocol section is used to indicate the protocol being used by the transport layer. This could be TCP, UDP, or  
something else.  
Time to live  
The time to live section is used to prevent a frame from traversing the network forever. This field contains a number  
(maximum 255) that is set when the frame is originally generated. Each time the frame is passed through the  
bridge/router, the bridge/router will decrement the time to live by two. When the time to live reaches zero, the  
frame is discarded.  
Header Checksum  
The header checksum is used to verify the data in the IP header. The IP header is recalculated each time a frame is  
passed through a router. The recalculation is necessary because the time to live field is changed.  
Fragmentation  
Fragmentation occurs when an IP frame must be split up into smaller IP frames. When the originating device  
generates the IP frame, the device is not aware of all the paths the frame must traverse to get to the destination  
device. If the IP frame is to pass through a network that has small packet capabilities, the IP frame must be split up  
and reassembled at the destination device. Each of the fragments is assigned a fragment offset value, which  
determines where the fragment fits into the original IP frame.  
The router will accept fragmented frames directed to itself and reassemble them, but it will not fragment frames.  
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Introduction  
Options  
There are various options that may be set for any IP frame.  
Source Routing  
Source routing is used to predetermine the path that the IP frame must travel through the network. There are two  
types of source routing: strict source routing and loose source routing.  
Strict source routing will contain a list of IP addresses of routers that must be used when the IP frame is sent through  
the network. Strict source routing is used mainly to provide some type of data security. Once the IP frame has  
reached the destination station, the destination station will take the list of IP addresses from the options field, reverse  
them, and use them for a strict route back to the originating station.  
Loose source routing will also contain a list of IP address of routers to be used on the path to the destination station.  
However, the IP frame may pass through other intermediate routers to get to the next IP address in the loose source  
routing list.  
Route Recording  
Route recording simply keeps a list of all the IP addresses of the routers that the IP frame has passed through on its  
way to the destination station.  
Time Stamps  
The time stamp option is used to record the time at which the IP frame passed through each router on its way to the  
destination station.  
ICMP Messages  
Internet Control Message Protocol (ICMP) messages are used to perform station and router protocol participation. ICMP  
messages are passed between routers, or between routers and stations. There are several different messages, as discussed  
below.  
Unreachable  
The “unreachable” message is sent back to the originating station when the path to the destination network has  
disappeared. A destination network may be unreachable because of a broken link, a downed router, a downed  
station, or other reasons.  
Redirect  
The “redirect” message is sent to the originating station when there is a better router to use to reach the destination  
network. Because the routers share routing tables, each router has the ability to determine whether it is the best  
router to use for network traffic. Once a station receives a redirect, all future IP frames destined for the particular  
destination network will be sent to the new router.  
Quench  
The “quench” message is sent to the originating station when the path to the destination network has become  
congested. The originating station will slow down the rate of transmission of frames for an internally (to the station)  
predetermined period of time upon receiving a quench message.  
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Introduction  
Ping  
The “ping” message is actually a query status message that may be sent to devices on the LAN to determine their  
operation status. The LAN device will reply with a message if it is active.  
Time and Mask server  
Two other ICMP messages are used to query the time and/or subnet mask from a particular LAN device. A message  
is sent to a LAN device asking for the time or mask, and the device replies appropriately.  
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Introduction  
RIP—Routing Information Protocol  
The most important function of the IP protocol is routing. IP routers constantly exchange information keeping their routing  
tables up to date. A method of communication is required to ensure compatibility between all IP routers in the network. RIP  
is the portion of the IP protocol that is used for router communication.  
Route Tables  
Each router will maintain a table of network addresses and the appropriate action to take with an IP frame it receives.  
A routing table entry will usually consist of the following items:  
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Network or sub-network address  
IP address of the next hop router  
Network interface to use to get to the next hop router  
Subnet mask for this network interface  
Number of hops to reach the destination network  
Number of seconds since this route was updated  
When a router receives an IP frame, the router will examine it to determine the destination network address. The  
router will then look in the routing table, determine the next router to send the IP frame to, and send the frame to  
that router.  
The selection of the best route path is based solely on the number of hops to the destination network.  
Update Mechanism  
In order to ensure that the routing tables of all routers in the network are kept up to date, each router will broadcast  
its routing table onto each of its locally connected networks. The broadcast of the routing tables occurs every 30  
seconds.  
The process of updating a routing table with current information, and deciding which router to use to reach a  
destination network, creates a ripple effect of changes through the network. When a router goes down and an  
adjacent router determines that the path has disappeared, the remaining adjacent routers on that network must  
determine the next path to use to reach the destination network. Each router will now broadcast its new routing table  
with the updated information. The updated information will propagate through the network until all routing tables  
have been brought up to date. This process is called convergence.  
The broadcast of the routing tables is also used as a method of determining whether a router is still alive or has been  
removed from the network. If a router has not heard from an adjacent router in 180 seconds, the local router will  
mark the adjacent router as unreachable and start to adjust the routing table, if necessary.  
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Introduction  
IPX Routing and The P1705 & P1730 Routers  
The router may be used to route between IPX networks.  
Novell Netware uses a suite of protocols for LAN communications. The Novell protocols include IPX, SPX, RIP, SAP, plus  
others, and operate at layers 3 and above. These protocols, their relationship with each other, and the general operation of a  
Novell network are discussed in this section.  
The Netware Network Operating System implements the concept of “Client-Server” computing. In this system, there are  
various Servers, such as File Servers, Print Servers, and Fax Servers, to name a few. The Client stations, where the users  
work, connect to these servers to retrieve files, get application software, or submit print jobs. Most of the interaction between  
the Clients and Servers is invisible to the users. These operations rely on the transfer of packets between Clients and Servers  
using the IPX/SPX protocols.  
IPX Addressing  
The IPX protocol is based on the Xerox XNS protocol. The IPX header contains all the IPX addressing information, and not  
much else.  
Network Layer Addressing vs. MAC Addressing  
An Ethernet frame has at least two levels of addressing. The MAC addresses for both the source and destination are  
contained in the MAC header. The MAC addresses are essentially physical port addresses, and are globally unique.  
Hardware vendors encode the port MAC address as part of the manufacturing process. All Ethernet devices have the  
same MAC address format. The MAC address is used to communicate frames between LAN ports regardless of  
protocol.  
The Network layer addressing is assigned by the network administrator, in a format prescribed by the layer 3  
protocol, for example IPX. The network address is used to structure the network system and for communications  
between ports operating the same protocol.  
Note that it is possible for a single network port to have several different network addresses, but it can have one and  
only one MAC address. An example of this is a computer acting as an IPX File Server, an IPX Router, and an IP  
Router. In this case the port would have a MAC address, an IPX address for its IPX functions, and an IP address for  
the IP Routing functions.  
IPX Address Format  
The IPX Address is made up of three components: the Network Number, the Node Number, and the Socket  
Number. These components are fixed length (unlike the IP addressing) and function.  
Figure 1 - 3 IPX Address Format  
Network Addresses  
The Network Number addresses the network. All stations on the same “network” will have the same Network  
Number. Note that a network could be a single segment, or multiple segments joined by either bridges or repeaters.  
In IPX internetworks, routers must be used to join different networks together.  
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Introduction  
Node Addresses  
The Node Number identifies the individual stations in a Network. In IPX devices, this address is assigned  
automatically and is identical to the MAC address. This means that the Node Number is self-configuring, and will be  
unique within the Network because the MAC address that was copied is (supposed to be) unique.  
The use of the MAC address as the Node Number allows IPX stations to be self-configuring. This makes the initial  
configuration of a station much simpler, but there are factors to consider before doing this. The Node Numbers  
cannot be assigned in a way that you might desire; for example with groups of stations having consecutive addresses.  
Instead, the network is forced to use whatever MAC address is assigned to the LAN port.  
Socket Addresses  
The Socket Number identifies the process within the source/destination that is communicating. Common Sockets  
include File Servers (Socket Number 0451), SAP (Socket Number 0452), and RIP (Socket 0453). The Socket  
Number can be thought of as the address of the upper layer using the IPX communication.  
The Socket Numbers are assigned by Novell and do not change from LAN to LAN. In other words, all  
communications with File Servers use Socket Number 0451. When a software vendor uses IPX to communicate  
across a Netware network, the vendor will apply to Novell to receive a Socket Number for the application. As an  
example, if Acme Schedule Company made a groupware scheduling program for Netware, they would get a Socket  
assigned for their use. No other communications on the LAN would use the Acme Scheduler Socket.  
Other IPX Header Information  
The IPX header contains some other information besides the source and destination addresses.  
Figure 1 - 4 IPX Header  
The checksum is a hold-over field from the XNS model used by Novell. The checksum is no longer used and this  
field is now permanently set to FFFF.  
The length field indicates the total length of the IPX packet. Note that the data portion can be any length up to 546  
bytes, so the length field is needed in the header.  
The Transport Control field is used for counting the number of routers the frame has traversed. In other words, it is  
a hop count. This operation uses only 4 of the 8 bits; the remaining 4 bits are reserved (by Novell) for future use so  
we could see additional information contained in the Transport Control field if Novell decides to use the excess  
capacity.  
The Packet Type indicates what type of service is using the packet. Some common packet types include type 1, RIP;  
type 2, Echo; type 4, IPX; and type 17, Netware Core Protocol.  
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Introduction  
Establishing an IPX Connection  
The Netware model is Client/Server, where Clients initiate calls to Servers for various purposes. The Clients are made aware  
of the presence of Servers by listening for Service Advertisement Protocol (SAP) broadcasts. Servers send SAP broadcasts  
regularly to identify themselves, including their address and what type of service they offer (File Server, Print Server, Fax  
Server, etc.).  
Services also are referred to by their name. Server names are assigned by the network administrator, and are usually  
representative of the server’s function. As an example, a network might have three File Servers named “GeneralFS”,  
“OrderProcessingFS”, and “DevelopmentFS.” Each of these servers would send out SAPs to inform the Clients of their  
presence. The Clients can display a list of Servers, and initiate a connection to the desired server using the servers name.  
Typically, Clients are pre-programmed with the name of the “Preferred Service,” which allows the Client station to connect  
automatically (without human intervention) to the Preferred Server. When no Preferred Service is set, the Client automatically  
connects to the first Server it hears. This is because a Client without a Server is almost useless in most Novell applications.  
Once an IPX connection has been established between a Client and the Server, there is often a security screen to manage  
access. File Servers are protected by a User ID/Password scheme to ensure that only authorized users are let into the server.  
Access privileges within the server are also assigned to the individual users. This prevents a Client logged into the “General”  
server from accessing files which are the private property of another user on the same “General” server.  
Service Advertisement Protocol  
The SAPs are broadcast by Servers at regular intervals, and collected by Clients so that they can keep track of what Servers are  
out there. Also, a Client may broadcast a Server Request (“Is there a Server named ‘XYZ’ out there?”), which would be heard  
by all Servers, and hopefully the Server which the Client is searching for would respond directly, telling the Client about itself  
(the Server).  
SAP Broadcasts  
The Service Advertisement Protocol broadcast is the standard mechanism that Servers use to announce their  
availability to the rest of the network. A server will broadcast a SAP containing from 1 to 15 different Services  
offered. Therefore if a single high-end PC is acting as a File Server, a Print Server, and a Fax Server, it would send  
out a single SAP that lists all three available Servers. Other servers that offer only a single Service would have only  
the one Server in the SAP.  
SAP broadcasts are sent out every 30 seconds. They are received by all stations on the LAN (it is a broadcast after  
all), and the station decides what to do with it. Both Clients and Servers maintain a list of all Servers that are  
broadcasting availability. A Novell user can execute the SLIST.EXE program to display the current list of known  
servers.  
When a Client or Server notices that a Server from its known Server list has missed a broadcast (it should get one  
about every 30 seconds), it starts up a counter, and when the Server has missed 3 broadcast intervals (about 180  
seconds) that Service is removed from the known Server list. In this way Servers that crash or go off-line for any  
reason are aged out of the network.  
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Introduction  
SAP Requests  
Sometimes Clients will need to find out if a specific Server is available. This may occur immediately after a Client is  
brought up, and before it has received any SAP broadcasts. The Client (or a new Server) sends out a SAP Request  
broadcast asking for a specific Server. That Server, or a router with the best route to that Server, will respond to the  
Client (Server) making the request.  
Server Types  
There are many different types of Servers. Each type is defined and given a type code by Novell. When new types of Servers  
are invented they will be assigned a new Server type. Some common Servers are:  
Type  
0000  
0003  
0004  
0005  
0006  
0007  
0009  
0024  
0027  
Description  
Unknown  
Print Queue  
File Server  
Job Server  
Gateway  
Print Server  
Archive Server  
Remote Bridge Server  
TCP/IP Gateway  
Routing Information Protocol  
The Novell Routing Information Protocol (RIP/X, where the X indicates IPX) is similar, but not identical, to the Routing  
Information Protocol used in IP routers. Novell RIP/X performs similar functions to IP RIP, in that RIP/X is used to  
communicate information about routes through routers to remote networks.  
RIP/X Operation  
The operation of RIP/X is, for all intents and purposes, identical to the operation of IP RIP. Routers send out  
broadcasts every 30 seconds containing the contents of that router’s route table (the list of best routes to known  
remote networks). When a router comes on line, the extent of its route tables will be its explicit route. In the case of  
a local router, it will be a route between the two networks to which the router is connected. In a pair of remote  
routers linked via a WAN connection, the first RIP broadcasts will contain only the route to the remote network. As  
time goes on, and assuming there are more routers in the network (and correspondingly more remote networks), the  
various routers will by way of RIP broadcasts inform each other of the various routes.  
RIP/X Broadcasts  
A RIP broadcast is sent out by IPX routers every 30 seconds or so. Each broadcast may contain information on up  
to 15 different routes (to 15 different networks; of course). If a router knows of more than 15 networks it will send  
out two (or more) broadcasts.  
Note that to spread the network overhead a router will stagger the generation of RIP/X and SAP broadcasts. The  
router will send a RIP/X broadcast, followed 15 seconds later by a SAP broadcast, followed 15 seconds later by  
another RIP/X broadcast, etc., etc. The SAP and RIP/X broadcasts are sent every 30 seconds as required, but they  
are staggered by 15 seconds to spread the overhead.  
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Introduction  
RIP/X Requests  
A Client may also request a route to a given network or server. To do so, the Client generates a Route Request  
broadcast that the routers hear, and routers that know of the route requested will respond to the originating station.  
In this way a new Client may find routes without waiting for the routers’ broadcast, that could be up to 30 seconds  
away (if it just missed one). A new router on a network will also broadcast a general Route Request to fill its route  
tables quickly. Again, without this mechanism the router would have to wait for about 30 seconds until it heard from  
all other routers via their standard RIP/X broadcasts.  
RIP/X Metrics  
The RIP/X routing protocol measures routes based on two metrics, the hop count and the ticks delay. These metrics  
are used to compare different routes to the same network, with the goal of selecting the best (shortest) route.  
The ticks delay is the primary metric used to determine the optimal route. The tick count is an indicator of how long  
a packet will take to get to the destination. Novell has defined 1 tick to be the length of time it takes a 512-byte  
frame to be transmitted on a 10-Mbps (Ethernet) LAN. This works out to about 18 ms. The real value of the tick  
delay is when evaluating routes across WAN connections. In these cases, the tick count is dependent on the link  
speed of the WAN connection(s), where a slower link will have a higher tick count.  
The hop count is the secondary measure of the length of a route; it is exactly the same as the IP hop count. If a route  
goes through 1 router (the shortest route), it will have a hop count of 1. If a route goes through 6 routers, the hop  
count for that route will be 6. The maximum number of hops RIP/X supports is 15, but this is a very large number,  
considering the size of most internetworks. When two or more routes to the same network have the same tick count,  
the router will use the route with the smallest hop count.  
Bridging and the P1705 & P1730 Routers  
The bridge portion of the P1705 & P1730 router is an Ethernet Media Access Control (MAC) level bridge providing an  
efficient means of interconnecting IEEE 802.3 Local Area Networks supporting a choice of standard Ethernet (10Base5),  
Thin Ethernet (10Base2) and Twisted Pair (10BaseT) interfaces. With the support of these industry-standard LAN interface  
technologies, the P1705 & P1730 routers will resolve the media conflicts that might have otherwise prevented the  
consolidation of these resources.  
The P1705 & P1730 routers will also fit right into those environments that may require more than one bridge by using the  
IEEE 802.1D Spanning Tree Protocol. With this protocol, the P1705 & P1730 routers will perform automatic network  
reconfiguration in the event of a link failure to one of the LAN segments. This provides maximum availability of the attached  
LAN services.  
Immediately following are several short descriptions of LAN bridging operations specific to the P1705 & P1730 routers.  
These descriptions will help you understand the concepts of bridging and how the P1705 & P1730 routers performs these  
functions.  
The remaining sections of this document describe how these functions are performed and configured. You are urged to  
spend the small amount of time necessary to familiarize yourself with the P1705 & P1730 router and the advanced functions  
it may perform for you.  
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Introduction  
The Initial Bridging Process  
Each time a router is powered up, it will perform extensive hardware and software tests to ensure the integrity of the unit and  
its attached LAN and Link interfaces. Upon successful completion of the power-up diagnostics, the router will follow rules  
to “learn” several aspects of your LAN environment. These rules define what actions are taken under particular situations.  
One of the more important rules employed by the router is also a very fundamental part of the bridging process. This rule  
dictates how Ethernet Station Addresses are processed by the bridge. The process is outlined below:  
Station Address Learning  
The router performs an important bandwidth-conserving function by a process termed Station Address Learning.  
This process determines the location of all active LAN Stations by monitoring the Ethernet frames being transmitted  
onto the LAN segments. Once it has learned the location of each station, the remote bridge/router will not forward  
those Ethernet frames destined for a station if the receiving station exists on the same LAN. Under these conditions,  
the bridge/router will only forward a frame if the location of the destination station has not yet been learned, or if the  
location has been determined to exist on the other LAN segment.  
To perform this process, the router follows the steps outlined below:  
Learning Local Addresses  
When the bridge/router is powered up, and after completing the power-up diagnostics, it will not immediately begin  
forwarding frames between LAN segments. Instead it will listen to local LAN activity in order to learn the location  
of each station address on each side of the bridge.  
The bridge/router captures each frame and looks at the source address contained within the Ethernet frame. Since  
the bridge/router knows which LAN segment the frame was received from, it can determine that this station must be  
located on this segment. As a result, it has just learned the location of the station.  
This process will continue for the period defined by the Forwarding Delay option, and in this fashion the first stage  
of the LAN address table is built.  
Forwarding  
Once the initial learning process is complete, the bridge/router enters a forwarding mode and examines frames that  
may need to be forwarded. The learning process does not stop at this time, however: The bridge/router will continue  
learning new stations as they become active on a LAN segment.  
Local Destination Addresses  
When a frame is received from a station on one segment, the frame is examined for the source address to ensure that  
this station has already been entered into the address table. If the source address exists, the Ethernet destination  
address is then viewed. The bridge searches the previously built address table for the location of the destination  
station. If it is determined that the location of the destination station exists on the same LAN segment (i.e. the  
destination address is local and the frame does not need to be forwarded across the bridge to the other LAN  
segment), then the bridge will “filter” and discard it.  
Initially, the bridge will only recognize those addresses that are local to a specific LAN segment. The bridge will  
thereby filter (discard) all local packets and forward all unknown non-local packets to the second segment located on  
the outbound port across the bridge.  
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Introduction  
Forwarding Unknown Destination Addresses  
When a frame is received from a LAN segment with an unknown destination address (an address that does not yet  
exist in the filter table), the bridge will forward the frame to the other segment, logging the address, and marking the  
location as “unknown”.  
Unknown Location Update  
When the receiving station transmits a frame in the opposite direction, the bridge will now see the previously  
unknown destination address in the source address field. It will now process this source address as it did during the  
initial learning stage, adding the location to the address entry.  
In this fashion (looking at source addresses of non-local packets), the bridge learns about non-local stations and their  
associated arrival ports. The bridge then updates the location of each address in its table. In the future the bridge  
will look up these stored non-local addresses to determine the bridge port on which to forward a packet destined for  
a known non-local station.  
In summary, the router will “learn” the location of a station by examining the source Ethernet address, and will  
“filter” frames based on destination address. A frame received from one segment that is of “unknown” location  
will be forwarded to the other segment. A frame that is received with a source address equal to a known address,  
but previously marked as an unknown location, will be updated in the filter table to add the location.  
Aging Timer  
During the bridging process, the filter table is built giving the location (bridge port or LAN segment) of known Ethernet  
addresses. The table would become quite large, eventually reducing performance, if stations were added, removed, or moved  
without the old information being purged periodically. Performance is affected since the larger the table, the more time it will  
take to process an incoming frame.  
This purging process, called “aging,” is an integral part of the learning function. It limits the size of the filter table and ensure  
that performance is not reduced unnecessarily.  
Aging assumes that many of the addresses may not be active all of the time, and could be purged after a specified interval to  
keep the size of the filter table small. In general terms, the smaller the table, the higher the performance.  
Address Purging  
To achieve this routine housekeeping, each entry in the filter table contains the LAN addresses, the LAN port  
identifier, and a timer flag. Each time a particular address is looked up or added to the table, a timer flag is set for  
the “fresh” entry. When a time interval, defined by the Bridge/Router Manager expires, the address table is scanned  
and any “stale” entries that have not been used since the timer expired are removed. This timer is called the “aging  
timer” and may be controlled through the bridge options.  
Purging the address does not prevent the station from using the bridging facilities, since the location of the station  
may be re-learned. However, since a small aging timer value will mean that the bridge must re-learn addresses more  
often, there must be a balance between table size and aging time to achieve optimal performance.  
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Introduction  
Aging Exception  
“Permanent” address entries are an exception to the aging rule. A permanent address is one that is not subject to the  
aging timer and will remain in the filter table for an indefinite period of time.  
A table is reserved for permanent address entries, separate from the table that is used for those non-permanent entries  
that are subject to aging. These tables may be displayed and modified with the bridge/router options discussed in  
this manual. Access is made locally from each Bridge/Router Console or one bridge/router can be made Master,  
able to control all functions of a partner router.  
Filled Address Table  
The filter table can hold 2048 address entries.If filter address table becomes filled, the following automatic procedure is  
followed:  
This procedure defines that an address that is not in the table will not be added and will be treated as any other unknown  
address. The frame will be passed to the other segment. An alarm will also be generated with the message “Station Address  
Table Full,” and from this point, another alarm will be generated only if in the meantime the table empties by 1/3 and then  
fills up again.  
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Introduction  
Router Feature Definitions  
Telnet  
A Telnet LAN station or another router has the ability to connect to the Operator Interface of any router supporting the  
Telnet feature. With the Telnet feature, all routers on a network may be managed from a single point.  
Once a connection is established, all of the menus of the other bridge/router are now available on the bridge/router that  
initiated the connection. All menu operation on the initiating bridge/router is suspended during the connection. Entering a  
control-C character <^C> at any time during the connection will cause a disconnection, and you will be back to the menu of  
the first bridge/router.  
To implement the Telnet feature, each bridge/router requires an IP address (see the Internet Set-Up Menu). It is advisable to  
assign an IP address to each router in your network.  
The IP address of another bridge/router may be assigned a name to simplify the connection process. Telnet connection to the  
other Router may be established by entering either the name or the IP address of that router. Refer to the Remote Site Set-Up  
Menu (under Configuration / WAN Set-UP) for more information on adding names to the bridge/router.  
If a bridge/router does not have an IP address, Telnet connections cannot be initiated or received.  
If a Telnet connected bridge/router receives a second connection attempt from another bridge/router the connection attempt  
will be ignored.  
Connecting to a bridge/router while the remote bridge/router menu system is operating with a different terminal setting may  
cause unexpected screen errors. Once the connection to the bridge/router has been established, it is recommended that the  
operator change the terminal setting to be the same as the initiating device.  
When a Telnet connection is made to a bridge/router, ensure that the Telnet session is in character mode, and carriage return  
padding (or translation) is set to NULL (or no translation). The extra character sent when carriage return padding is on will  
cause some displays to behave erratically.  
Link Compression  
The router’s optional compression feature multiplies the effective data throughput across wide area links operating at speeds  
from 9600 bps through to 256 Kbps. The exact amount a given transmission can be compressed is dependent upon the type  
of data being transferred over the wide area network. As an example, because of their repetitive make-up, most graphics and  
database files can easily be compressed by a ratio of 6:1. In contrast, other types of files (such as binary files), that are not as  
repetitive, typically yield a compression ratio of 2:1. It should also be noted that compression ratios are entirely dependent  
upon the make-up of the specific file — while it may be possible to compress a given ASCII file far beyond the 6:1 ratio, a  
different ASCII file may only compress to a ratio of 4:1 or lower.  
At link speeds above 256 Kbps, link compression is not advised as the processing time involved in compressing the data does  
not yield significant gains over the transmission of raw data.  
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Introduction  
7
6
5
4
3
2
1
0
Compression Ratio  
File Type  
Figure 1 - 5 Typical Compression Ratios by File Type  
Data compression will give a 56/64 Kbps link an effective throughput range from 112/128 Kbps when transferring binary  
files, to 364/384 Kbps when transferring graphic files. This increased throughput significantly reduces the bandwidth  
required across the WAN link to achieve a given performance level and/or allows the use of lower-cost transmission facilities.  
400  
Uncompressed  
350  
Compressed  
300  
250  
200  
150  
100  
50  
Throughput in  
Kbps  
0
Binary  
Mixture  
Graphic  
File Type  
Figure 1 - 6 Typical Throughput Over 56 Kbps Link  
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Introduction  
WAN Topologies  
The router may be connected to other routers in two configurations: Multipoint or Point-to-Point. The WAN routing  
method used is set in the WAN Set-Up Menu under the Link Operation option.  
Point-to-Point  
In a Point-to-Point configuration, two routers are connected together with one or two WAN links. Each link may be  
set to an always active (unconditional) state or a backup/recovery (conditional) state.  
A single link may be used for general traffic, and the second link may be used for disaster recovery or increased  
throughput. The Bandwidth on Demand feature controls the conditional behavior of the second link in a Point-to-  
Point configuration.  
The Time of Day connect feature may be used in a Point-to-Point configuration to provide specific hours of access  
or increased throughput.  
Multipoint  
In a Multipoint configuration, an router is connected to more than one other router. A Multipoint configuration  
consists of three or more routers connected together on the same wide area network.  
A dual-link router that is connected to two different routers (one on each link) is in a Multipoint configuration.  
The Time of Day connect feature may be used in a Multipoint configuration to provide specific hours of access.  
Bandwidth On Demand  
Each router has the ability to automatically enable or disable a second link based on traffic activity, time of day, or main link  
failure.  
The Bandwidth on Demand feature allows you to use a second link only when required, thus saving the cost of having the  
second link up and connected all of the time. The second link could be connected to an inexpensive dial-up line that is only  
required when the main link fails or is exceeding a predefined traffic throughput level.  
Bandwidth on Demand is accomplished by using the intelligence of the router to measure the utilization of the primary link.  
When it approaches saturation, Bandwidth on Demand will initialize and loadshare with a second stand-by link. This will  
effectively increase the throughput of the router, thereby alleviating the saturation and avoiding data loss. The second link is  
then deactivated when traffic levels drop off to where the primary link can adequately handle the traffic load once again.  
When the stand-by link is activated, the router raises the outgoing control signals. This control-signal transition is then used  
to initiate autodial or auto call-setup procedures on the interface device. This autodial feature is standard on most of the  
modems and terminal adapters on the market.  
When the second link is deactivated, the router lowers the outgoing control signals. This control-signal transition is used to  
disconnect the call and bring down the link. The second link then remains in stand-by mode until the bridge/router  
determines that the link must be used again.  
To set up a Bandwidth on Demand installation, you would first connect the second link of the router to a public circuit-  
switched network using the appropriate interface device. You would use high-speed modems with telephone lines, terminal  
adapters with an ISDN network, or digital modems with switched digital services.  
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Introduction  
This second link would now be placed in a stand-by mode by setting Conditional operation option in the Secondary  
Activation Menu to Enabled.  
Now you must choose the throughput level that will be required for activating the stand-by link. The throughput level is  
measured in percentage of use of the primary link. This percentage level is defined by the Up Threshold parameter in the  
Secondary Activation Traffic Set-Up Menu and may be set to any value from 50% to 100%.  
A timer must be defined to determine the length of time to wait before bringing up the stand-by link. The Up Stability Timer  
parameter in the Secondary Activation Traffic Set-Up Menu is used to define how long in minutes (from 1 to 60) the main  
link must exceed the threshold before the stand-by link is started.  
Once the activation-throughput threshold has been determined and set, you must decide what the throughput threshold will  
have to be to drop the second link and operate on the main link only.  
The Down Threshold level is set in the Secondary Activation Traffic Set-Up Menu and defaults to 10% lower than the Up  
Threshold level. Remember that the down threshold looks at the total throughput (both links together) to determine if the  
second link will be brought down. The Down Threshold is defined as the percentage of the main links bandwidth the current  
total throughput represents. When the total throughput drops below the Down Threshold, the second link will be dropped.  
A timer must also be defined to determine the length of time to wait before dropping the stand-by link. The Down Stability  
Timer parameter in the Secondary Activation Traffic Set-Up Menu is used to define how long in minutes (from 1 to 60) the  
combined links’ throughput must remain below the down threshold level before the stand-by link is stopped.  
Time of Day Connect Application  
In addition to the Bandwidth on Demand feature, the router has the ability to establish link connections based on a  
specific time-of-day schedule. Either one or two links may be controlled using the Time of Day feature. The Time  
of Day feature may also be used in conjunction with the Bandwidth on Demand feature. It may be used in both  
Multipoint and Point-to-Point configurations.  
Point-to-Point  
One example of a Point-to-Point configuration would consist of a head office and a remote office. Cost comparisons  
might reveal that it is less expensive to use a dial-up line during business hours only instead of a permanent leased  
line.  
One router will be installed at each office, and the link from each bridge/router will be connected to a dial modem.  
Set the link operation of the bridge/router at the head office to Conditional, and then enter a time schedule by using  
the Time Schedule option of the Activation Conditions Menu. The modem connected to the head-office  
bridge/router will have an autodial number of the modem at the remote office. With the time schedule set to have  
the link active from 8 am to 6 pm each day of the week, the router will establish the link and keep it active during  
those hours only. The time selection may be made in half-hour (30-minute) increments.  
Another example of a Point-to-Point configuration would consist of two routers connected together with one link  
pair, with the other link pair being used for Time of Day connection. This extra link could be needed during specific  
times for predicted traffic increases.  
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Introduction  
Multipoint  
A simple Multipoint configuration would consist of a head office and two remote offices. Cost comparisons might  
reveal that it is less expensive to use a dial-up line during business hours only instead of a permanent leased line.  
One router will be installed at each office (for a total of three units). Each router at the remote office locations will  
connect to a separate link on the router at the head office. The link from each bridge/router will be connected to a  
dial modem. Set the link operation of both links on the bridge/router at the head office to Conditional, and then  
enter a time schedule for each link by using the Time Schedule option of the Link Activation Conditions Menu. The  
modems connected to the head-office bridge/router will each have an autodial number of one of the modems at the  
remote offices. With the time schedule set to have the link active from 8 am to 6 pm each day of the week, the  
router will establish the link and keep it active during those hours only.  
Disaster Recovery Backup Link  
Each Single Active Link router has the ability to activate a secondary link when the main link fails. This secondary link may  
be connected to a dial-up modem or ISDN service, so it can be used if something should happen to the main link. The  
secondary link is available only for a disaster-recovery situation.  
ISDN Single Active Link & Dual Active Link  
On Single Active Link ISDN Routers, when the WAN Environment option is set to Multipoint, only ISDN call 1 is  
available; ISDN call 2 is disabled. A Single Active Link ISDN router will be able to use both ISDN calls to connect in a  
Point-to-Point topology to another ISDN router.  
On Dual Active Link ISDN Routers, the WAN Environment option may be set to either Point-to-Point or Multipoint. Both  
ISDN calls may be used to connect to the same ISDN router or to two other ISDN routers.  
Operating Software Upgrades  
The router includes flash memory, that allows new system code to be downloaded using the Trivial File Transfer Protocol  
(TFTP). This allows software updates to be performed quickly and painlessly from a host server (with TFTP capabilities) on  
the network.  
The Router also allows the downloading of software updates by using a direct management port connection and the  
ZMODEM transfer protocol.  
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Section 2 — ISDN Connection Management  
ISDN Connection Management  
In the world of ISDN the ability to decrease connection time is a financial bonus in the LAN interconnecting marketplace. If  
ISDN connections can be controlled so that a minimum amount of cost is incurred while full LAN interconnecting  
functionality is retained, the overall cost for WAN communications can be minimized.  
In many LAN protocols, the interchange of data is sporadic and frequently long periods of time exist between successive data  
transfers. If ISDN calls can be disconnected during the periods of inactive data transfers without the LAN connections being  
aware of the disconnection, the ISDN call time and cost is reduced.  
To accomplish this, the router’s Connection Management function actively tracks all of the LAN connections and maintains  
them while the ISDN call is deactivated. When the LAN devices require the connection to exchange more data, the ISDN call  
is reactivated so that the LAN data may be transferred.  
During the periods of ISDN call disconnection (suspension), each end of the LAN connection must believe that the complete  
connection still exists. The generation of the regular status inquiries and responses normally generated by the two devices  
involved in the LAN connection is performed by the ISDN bridge/router while the ISDN call is suspended.  
Wide Area Network Topologies Supported  
Two types of Wide Area Network (WAN) topologies are supported with Connection Management  
1. Two Routers connected.  
2. Three Routers connected in a star configuration.  
Connection Management is not functional when routers are connected in a ring.  
Call Establishment Methods  
ISDN calls may be established according to the following connection methods:  
1. Auto-Call  
2. Address Connect  
3. Manual call  
4. Combination  
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ISDN Connection Management  
Auto-Call (Time-of-Day Connections)  
An Auto-Call connection is an ISDN connection that is established each time the router attempts to start the  
link. This starting of the links occurs each time an router powers up or when the link goes through a restart or  
at the times specified by the Time-of-Day Activation Schedule. An Auto-Call connection would be used for a  
static WAN configuration that needs to be maintained at all specified times between sites.  
Network B  
This ISDN connection is made  
Network A  
upon initial power-up and  
is m aintained during the  
times defined in the  
tim e-of-day schedule.  
Figure 2 - 1 Auto-Call WAN Topology  
The semi-permanent connection that results from an Auto-Call configuration means that the router will attempt  
to maintain a connection to the partner router during the times specified in the Time-of-Day Schedule. When  
Connection Management is enabled, the ISDN call to the Auto-Call number may be suspended during periods  
of inactivity.  
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ISDN Connection Management  
Address Connect  
An Address Connect connection is an ISDN connection that is established to a specific destination router  
dependent upon the destination network address contained within traffic received from the local LAN.  
When a device on the local LAN wishes to establish a session with a device on a remote LAN, the local device  
will send a frame with a destination address of the remote device. The router will receive the frame and  
examine the destination network address contained within the frame.  
If the router can determine the route to the destination network address, the frame is passed along to one of the  
currently connected partner router. If the destination network is not located on a currently connected partner  
router, the local router will then look in the Address Connect table to determine which partner router to call.  
The Address Connect tables are used by the router to determine which remote router is called when a specific  
destination network address is requested from a device on the local LAN. The Address Connect tables are  
configured by the router operator.  
Network B  
555-2000  
Network A  
555-1000  
The ISDN connection is made  
to the appropriate remote network  
according to the entries in the  
Address Connect table.  
ISDN Network  
Networks C through G  
555-8000  
Rem ote Network ISDN Number  
Network B  
Network C  
Network D  
Network E  
Network F  
Network G  
Network H  
555-2000  
555-3000  
555-4000  
555-5000  
555-6000  
555-7000  
555-8000  
Network H  
Figure 2 - 2 Address Connect WAN Topology  
Manual Call  
A manual call is simply an operator initiated ISDN call to a remote partner router. The ISDN number is  
entered by the operator and a call is made.  
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ISDN Connection Management  
Combination  
A combination of the Address Connect and Auto-Call options may be configured when a semi-permanent  
connection is required to one remote site and a dynamic connection is required to multiple sites. A dynamic  
connection indicates that the remote site for the second ISDN call will change depending upon what destination  
IP address is required for the connection. One ISDN B-channel is configured to have an Auto-Call ISDN  
number and the other B-channel may be used for the Address Connect functions.  
Network X  
This ISDN connection is made  
using the first B-channel  
upon initial power-up and is  
maintained according to the  
Auto-Call param eters.  
Network B  
555-2000  
Network A  
ISDN Network  
555-1000  
The ISDN connection is made  
Networks C through G  
555-8000  
using the second B-channel  
to the appropriate rem ote network  
according to the entries in the  
Address Connect table.  
Remote Network ISD N Number  
Network B  
Network C  
Network D  
Network E  
Network F  
Network G  
Network H  
555-2000  
555-3000  
555-4000  
555-5000  
555-6000  
555-7000  
555-8000  
Network H  
Figure 2 - 3 Auto-Call & Address Connect WAN Topology  
Connection Process  
When a LAN client requests a session with a LAN server, the client will initiate the session by sending a session  
connection request to the server. If the server is located on a remote LAN, the session connection request must be  
sent to that remote LAN before the server can process the session connection request and reply to it. Any of the call  
establishment processes may be used to establish the ISDN call between the routers in order to establish a LAN  
session between the local and remote LANs.  
Once the client-server session has been established, keepalive or status packets are generated by either or both ends  
of the session. The keepalive packets are used to verify the status of the device at the opposite end of the session.  
When Connection Management is enabled, LAN sessions that are established across the ISDN calls are monitored  
and maintained in a table. The session table may contain up to 256 entries for each supported session type, with the  
router filtering all traffic for any sessions over the 256 limit of the table. The 257th and greater LAN sessions will not  
be allowed by the router.  
While an ISDN call is up and connected, all traffic within the sessions will be transferred to the partner router across  
the ISDN call.  
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ISDN Connection Management  
Protocol Awareness  
For Connection Management to be effective, each of the routers must be aware of the protocols used within  
the data being transferred over the ISDN calls between them.  
IP and IPX Client-Server sessions are established between devices located on the LANs that are routed by the  
Router. If the router is to manage the ISDN calls between the routed LANs, the routers on each WAN end of  
the Client-Server session must be aware of the session and also must become actively involved in the  
maintenance of the session. When an ISDN call is suspended, both the Client and the Server must still believe  
that the session exists.  
Suspension Process  
The router maintains a table for each ISDN call made to a partner ISDN router in order to determine when the  
ISDN call should be suspended during Connection Management.  
Any number of LAN sessions may be currently using the established ISDN call to transfer data between the  
client and the server. The router monitors the ISDN call for interesting traffic passed on each of the sessions  
currently using the ISDN call. If no interesting traffic is observed on the ISDN call for a period of time greater  
than the defined Idle Timer value, the ISDN call is suspended and disconnected. While the ISDN call is  
suspended, the router will monitor the LAN sessions for interesting traffic and re-establish the ISDN call when  
required.  
A suspended ISDN call may only be re-established by the router initiating the suspension or by the partner  
router that was connected just prior to the call being suspended. This prevents other routers from tying up the  
ISDN calls and interfering with the suspended calls.  
ISDN calls may be connected and disconnected between the two routers when required according to the  
suspension and re-activation of the ISDN calls. When all of the sessions using the call in the table have been  
closed, the call will be terminated and the ISDN B-channel becomes available for use to connect to a different  
ISDN router. When the connection to the partner ISDN router is configured to use Auto-Call, the ISDN call  
will be suspended when there are no sessions in the table.  
Interesting Traffic  
Interesting Traffic is defined as normal interactive user data for a session. Certain data exchanged during a  
normal session is not considered to be interesting and usually is composed of keepalive messages, watchdog  
messages, and routing messages. Non-interesting data is handled differently when Connection Management is  
enabled.  
Idle Timer  
In order to determine the criteria for suspending an ISDN call, an Idle Timer is defined. The Idle Timer defines  
the period of time that LAN traffic is monitored to determine when the ISDN call will be put in suspension and  
disconnected. When Interesting Traffic is observed once again, the call is reconnected.  
The Idle Timer is common to all ISDN calls and may be defined from 6 seconds to 5 minutes in 1 second  
increments. The Idle Timer may be disabled so that only the partner router determines when the ISDN call will  
be suspended.  
Session Participation (Spoofing)  
While an ISDN call is up and connected, all traffic within the sessions will be considered interesting and will be  
transferred to the partner router across the ISDN call. When the router determines that the ISDN call is to be  
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ISDN Connection Management  
suspended, the router will consider keepalive and routing information packets to now be non-interesting and  
will begin to generate and respond to keepalive and RIP packets.  
When the router receives a keepalive packet from the LAN for one of the sessions, the router will not activate  
the ISDN call and will not pass the keepalive packet to the remote LAN. The router will generate a response to  
the keepalive packet and send it to the originator of the packet. In this way, the router will keep the ISDN call  
suspended and will also keep the local side of the session active. The router at the remote site will also be  
participating in the keepalive process with the remote side of the session.  
While the ISDN call is  
suspended, this Router  
will generate keepalive  
frames and send them  
to the Client and wait for  
an acknowledement from  
The Client receives the  
keepalive frames and  
sends an acknowledged  
back to the Server.  
the Client.  
The Server generates keepalive frames  
which are to be sent to the Client and  
acknowledged by the Client.  
Suspended  
Server  
Client  
This Router will receive the keepalive  
frames destined for the Client and generate  
a response back to the Server on behalf of the  
Client while the ISDN call is suspended.  
Figure 2 - 4 Session Keepalive Messages  
While an ISDN call is suspended, if the router observes that one of the devices in the session stops sending  
keepalive packets, the router will begin to generate keepalive packets and send them to the device in order to  
determine the status of the device. The length of time the router waits before beginning to generate keepalive  
packets is definable by the operator.  
routers incorporate a settling time for routing updates. This means that an router will wait after an initial  
change in the network is reported before transmitting that change on to the remaining routers connected on the  
Wide Area Network.  
The will resume the suspended ISDN call in order to transmit routing messages to partner routers. If the  
ISDN call cannot be resumed, or has been closed, the routes will be aged out of the routing table.  
Termination Process  
When the router has determined that there are no sessions active on an ISDN call, the router will attempt to  
close the call. If the partner router still has sessions assigned to that call, the call will be maintained until each  
side has determined that there are no active sessions using the call.  
When the connection to the partner ISDN router is configured to use Auto-Call, the ISDN call will be  
suspended when there are no session in the table. The ISDN call will be re-established to the Auto-Call number  
the next time the router needs to send data to the partner ISDN router.  
If the operator of the router performs a link reset, the suspended call will be closed unilaterally.  
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ISDN Connection Management  
IP Specifics  
IP Address Connect  
As stated previously, an IP Address Connect connection is an ISDN connection that is established to a specific  
destination router dependent upon the destination IP address contained within IP traffic received from the local  
LAN.  
This means that the router continuously monitors IP traffic from the local LAN, as all IP routers do, and makes  
ISDN connections to partner routers when IP traffic needs to be sent to remote LANs. Once the IP traffic is  
passed to the remote LAN and all sessions are closed, the local router will then disconnect the ISDN call and  
continue to monitor the local LAN for IP traffic.  
The IP Address Connect table consists of IP addresses and associated ISDN numbers of remote partner IP  
Routers. Either one or both of the ISDN calls may be used for IP Address Connect use. When one of the ISDN  
calls is defined for Auto-Call purposes, the remaining ISDN call may be used for IP Address Connect use.  
The combination of Auto-Call and Address Connect allows part of the WAN environment to be established  
statically and still allow dynamic connections to other networks depending upon destination IP addresses.  
Suspension of TCP/IP Sessions  
When Connection Management is enabled, TCP sessions that are established across the ISDN calls are  
monitored and maintained in a table. The TCP session table may contain up to 256 entries. The will filter all  
traffic for any TCP/IP session over the 256 limit of the table preventing any new TCP sessions from being  
established.  
While an ISDN call is suspended, if the router observes that one of the devices in the session stops sending  
keepalive packets, the router will begin to generate keepalive packets and send them to the device in order to  
determine the status of the device. The length of time the router waits before beginning to generate keepalive  
packets is definable by the operator.  
If the device does not respond to five consecutive keepalive packets sent from the router, the router will  
determine that the device has gone away and the router will send a packet to each end of the TCP session to  
shut down the session. When the shut down packet is generated for the remote device, the router will re-  
activate the suspended ISDN call and transmit the shut down packet to the remote device. Once the remote  
router determines that the TCP session is no longer active, the remote router will stop generating and  
responding to the keepalive packets for that TCP session.  
RIP—Routing Information Protocol  
ISDN routers incorporate a 3 second settling time for IP RIP updates. This means that an will wait for three  
seconds after an initial change in the network is reported before transmitting that change on to the remaining  
routers connected on the Wide Area Network.  
28  
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ISDN Connection Management  
IPX Specifics  
RIP/IPX and SAP/IPX  
ISDN routers incorporate a 3 second settling time for IPX RIP and SAP updates. This means that an will wait  
for three seconds after an initial change in the network is reported before transmitting that change on to the  
remaining routers connected on the Wide Area Network.  
Suspension of IPX Sessions  
When Connection Management is enabled, IPX sessions that are established across the ISDN calls are  
monitored and maintained in a table. The IPX connection table may contain up to 256 entries. The will filter all  
watchdog traffic for any IPX session over the 256 limit of the table preventing any new IPX sessions from  
being established.  
Server IPX Watchdog Frames  
When the router on the server side of the IPX session receives an IPX watchdog packet from the server on  
the local LAN, the router will pass the watchdog packet to the remote partner router and then to the client  
side of the IPX session. Once the client side of the session has responded to the IPX watchdog, the router  
on the server side of the IPX session will consider all future IPX watchdog packets for this session to be  
non-interesting and will not pass them across the ISDN call.  
The router on the server side of the IPX session will generate a response to each IPX watchdog packet sent  
by the server and send the response back to the server on the local LAN. In this way, the local router will  
keep the ISDN call suspended and will also keep the local side of the IPX session active.  
While an ISDN call is suspended, if the router on the server side of the IPX session observes that the server  
has stopped generating IPX watchdog packets, the router will assume that the server has gone away and alert  
the router on the client side of the IPX session. The router on the client side of the IPX session will stop  
generating IPX watchdog packets for that IPX session.  
Client IPX Watchdog Frames  
When the router on the client side of the IPX session observes an IPX watchdog packet from the server side  
of the IPX session sent to the client, and later an IPX watchdog reply being sent from the client back to the  
server, the router on the client side of the IPX session will begin to generate and send IPX watchdog  
packets to the client on behalf of the server.  
While an ISDN call is suspended, if the router on the client side of the IPX session observes that the client  
has stopped responding to the IPX watchdog packets, the router will assume that the client has gone away  
and will alert the router on the server side of the IPX session. The router on the server side of the IPX  
session will stop responding to the IPX watchdog packets for that IPX session and will filter all remaining  
IPX watchdog packets generated by the server until the server has determined that the client has gone away.  
The time interval between the IPX watchdog packets generated by the router on the client side of the IPX  
session may be defined by the operator by setting the Watchdog Interval option in the IPX Routing Set-Up  
menu.  
IPX Serialization Frames  
The router will prevent IPX serialization frames from activating a suspended ISDN call by filtering the IPX  
serialization frames. The router will allow IPX serialization frames to be passed to the WAN when the ISDN  
call is active.  
29  
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Section 3 — Link Interfaces Reference  
Pinout Information  
Each link interface available is described with detailed information on pin designation. Standard interface  
cables will provide correct connections to modems, datasets, or DSU/CSUs.  
When connecting two bridge/routers back-to-back without modems, a null-modem cable is required to  
crossover the pins on the links. Crossing over the pins allows two bridge/routers both configured as DTE  
interfaces to be connected together. With this configuration, both bridge/routers will provide clocking for  
the links, and each bridge/router must have a link speed defined.  
V.35 Module Identification:  
V.35 links are provided as DB25 connectors on the back of the bridge/router, so an interface converter is  
needed to convert to the standard V.35 connectors.  
Link Clocking Information  
All of the link interfaces on the router act as DTE devices, this means that they may be directly connected to  
DCE devices (modems, etc.) with the DCE devices providing the clocking for the link. The link speed is  
controlled by the DCE device. Setting the link speed on the router will not result in a speed change on the  
link.  
Some DCE devices allow the DTE devices connected to them to supply a clock signal which is then routed  
back to the transmit clock pins on the DCE interface. This clock is then received by the link interface. By  
using this method, the router may be in control of the link speed. The link speed may also be controlled by  
the router when a null-modem cable is used to connect two routers in a back-to-back configuration.  
Changing the link speed within the menu system of the router changes the clock output speed that is  
generated on the DTE Terminal Timing pins on the link interfaces.  
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Link Interfaces Reference  
The –P1705 and P1730 routers are currently produced with LXT CSU/DSU interface modules which have  
their link speed configured in software (please see the PPP menus manual for configuration options);  
however, the earlier model ATL CSU/DSU module is still compatible with the router and may be used with  
it. Note that ATL master mode signaling is not compatible with the current standard 64K master mode  
signaling; therefore, for back to back connections, an ATL unit will only operate at 64K when connected to  
another ATL unit. If one interface is an ATL unit and the other is not, back to back operation must be set to  
56K.  
ATL CSU/DSU Link Module Information  
The ATL CSU/DSU link module is normally configured to receive clock from the connected network.  
When two ATL CSU/DSU link modules are to be used on a leased line in a back-to-back set-up, one of the  
modules must provide the clock.  
These modules may have either the UP/DOWN switch type or the ON/OFF slide switch type. Each type is  
illustrated below.  
Figure 3 - 1 Rear View of ATL CSU/DSU Link Module with UP/DOWN Switches  
Figure 3 - 2 View of ATL CSU/DSU Link Module with Sliding ON/OFF Switches  
When connecting two bridge/routers back-to-back with CSU/DSU link modules, a null-modem cable is  
required to crossover the pins on the links. Crossing over the pins allows two bridge/routers both  
configured as DTE interfaces to be connected together.  
Switch number 1 determines whether the ATL CSU/DSU link module will generate clocks or receive clocks.  
When switch 1 is down (on), the normal position, the module receive clocks from the connected network.  
When switch 1 is up (up), the module will generate clocks. When a pair of Routers are connected back-to-  
back with ATL CSU/DSU link modules one module must be set to generate clocks and one module must be  
set to receive clocks. On 64 Kbps units only, switch number 3 determines the mode of the ATL CSU/DSU.  
When switch 3 is down (on), the CSU/DSU is in DDS (Digital Data Service) mode for normal connection to  
the 64 Kbps digital service. When switch 3 is up (off), the CSU/DSU is in LDM (Limited Distance Modem)  
mode for back-to-back connection with a null-modem cable.  
On 56 Kbps units, the position of switch 3 is not a factor for back-to-back connection with a null-modem  
cable. Switch 1 must still be set as noted above.  
A DSU/CSU crossover cable would be constructed as follows:  
1 --> 7  
2 --> 8  
7 --> 1  
8 --> 2  
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Link Interfaces Reference  
Console Pinouts  
The connector shown here and pinouts described here correspond to  
the connector labeled “Console” on the back of the P1705 & P1730.  
1
13  
25  
14  
DB25 Female DCE  
CCITT  
Circuit  
Number Number  
Direction  
To From  
DCE DCE  
Contact  
Circuit  
Name  
Circuit  
1
2
3
5
6
7
8
20  
22  
101  
103  
104  
106  
107  
102  
109  
108.2  
125  
AA  
BA  
BB  
CB  
CC  
AB  
CF  
CD  
CE  
Protective Ground  
Transmitted Data  
Received Data  
Clear to Send  
Data Set Ready  
Signal Ground  
NA  
X
X
X
X
NA  
X
Received Line Signal Detector (CD)  
Data Terminal Ready  
Ring Indicator  
X
X
Figure 3 - 3 Console Pinouts  
The connecting cable must be a shielded cable.  
When connecting the router console directly to a modem, a null modem cable must be used because both  
the router console and the modem are DCE devices. A null modem cable with pinouts according to the  
following figure must be used.  
Contact Number  
Modem Contact  
Number  
8
3
20  
2
2
3
20  
7
8
7
4
5
5
4
22  
22  
Figure 3 - 4 Console Null Modem Cable Pinouts  
32  
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Link Interfaces Reference  
CSU/DSU Module:  
The CSU/DSU interface module uses a standard RJ45 service connector, pinout specification RJ48S.  
CSU/DSU  
Figure 3 - 5 Rear View of the CSU-DSU Connector  
The LXT411 CSU/DSU link connection is set to operate at 64 Kbps by default. The link may be set to 56  
Kbps via the software menus if required.  
When two CSU/DSU link routers are to be connected via a leased line in a back to back set-up, the unit  
must be set to 56 Kbps link speed and a null-modem crossover cable used for the connection.  
A DSU/CSU crossover cable would be constructed as follows:  
1 --> 7  
2 --> 8  
7 --> 1  
8 --> 2  
T1/E1 Module:  
The T1/E1 interface module use a standard RJ45 service connector, pinout specification RJ48C.  
T1/E1  
Figure 3 - 6 Rear View of the T1/E1 Connector  
When two T1/E1 routers are to be connected in a back to back set-up, a null-modem crossover cable used  
for the connection.  
A T1/E1 crossover cable would be constructed as follows:  
1 --> 4  
2 --> 5  
5 --> 2  
4 --> 1  
Pins 1 and 2 are receive (1 = ring, 2= tip)  
Pins 4 and 5 are transmit (4 = ring, 5= tip)  
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Link Interfaces Reference  
V.24 & RS232C Link Pinouts  
The connector shown here and pinouts described here correspond to  
the connector labeled “RS232/ V.24” on the back of the P1705 & P1730.  
1
13  
25  
14  
DB25 Female DTE  
CCITT  
Circuit  
Direction  
To From  
Contact  
Circuit  
Number Number Circuit  
Name  
DCE DCE  
1
2
3
4
101  
103  
104  
105  
AA  
BA  
BB  
CA  
Protective Ground  
Transmitted Data  
Received Data  
Request to Send  
NA  
X
X
X
5
----------  
6
7
8
107  
102  
109  
CC  
AB  
CF  
Data Set Ready  
Signal Ground  
Received Line Signal Detector (CD)  
X
NA  
X
9
----------  
10  
11  
12  
13  
14  
15  
16  
17  
18  
19  
20  
21  
22  
23  
24  
25  
----------  
----------  
----------  
----------  
----------  
114  
DB  
DD  
Transmit Signal Element Timing (DCE Source)  
X
----------  
115  
141  
Receive Signal Element Timing (DCE Source)  
X
Local Loopback  
----------  
Data Terminal Ready  
X
108.2  
125  
CD  
CE  
DA  
X
X
X
----------  
Ring Indicator  
----------  
Transmit Signal Element Timing (DTE Source)  
----------  
113  
Figure 3 - 7 RS232 Link Pinouts  
The connecting cable must be a shielded cable.  
NOTE For U.K. Approval:  
The connecting cable should be manufactured from Belden Cable, or a cable with equivalent specifications.  
Each end must be terminated in a male 25 pin X.21 bis connector as defined in ISO-2110 1989. The cable  
may be any length between 0 and 5M.  
34  
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Link Interfaces Reference  
V.11 & X.21 Link Pinouts  
The connector shown here and pinouts described here correspond to  
the connector labeled “V.11/X.21” on the back of the P1705 & P1730.  
8
1
15  
9
DB15 Female DTE  
X.21  
Direction  
Contact  
Number  
Circuits  
Reference  
Circuit  
To From  
DCE DCE  
Name  
Protective Ground  
Transmitted Data (A)  
Control (A)  
Received Data (A)  
Indication (A)  
1
2
3
4
5
NA  
T (A)  
C (A)  
R (A)  
I (A)  
X
X
X
X
X
6
7
S (A)  
Signal Element Timing (A)  
----------  
8
9
Ground  
T (B)  
C (B)  
R (B)  
I (B)  
Signal Ground  
Transmitted Data (B)  
Control (B)  
Received Data (B)  
Indication (B)  
NA  
X
X
X
X
X
10  
11  
12  
13  
14  
15  
S (B)  
Signal Element Timing (B)  
----------  
----------  
Figure 3 – 8 V.11 Link Pinouts  
The connecting cable must be a shielded cable.  
Circuits which are paired (contain an (A) and (B) reference) should be connected to twisted pairs  
within the connecting cable.  
NOTE For U.K. Approval:  
The connecting cable should be manufactured from Belden Cable, or a cable with equivalent specifications.  
Each end must be terminated in a male 15 pin X.21 connector as defined in ISO-4903 1989, but one end of  
the cable must have UNC-4-40 screws and the other end must have M3 screws. The cable may be any length  
between 0 and 5M.  
35  
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Link Interfaces Reference  
RS442 & RS530 Link Pinouts  
The connector shown here and pinouts described here correspond to  
the connector labeled “RS530” on the back of the P1705 & P1730.  
1
13  
25  
14  
DB25 Female DTE  
Direction  
Contact  
Number  
1
Circuit  
Name  
Protective Ground  
Transmitted Data  
Received Data  
Request to Send  
Clear to Send  
Data Set Ready  
To From  
DCE DCE  
NA  
X
Circuit  
Shield  
BA (A)  
BB (A)  
CA (A)  
CB (A)  
CC (A)  
AB  
CF (A)  
DD (B)  
CF (B)  
DA (B)  
DB (B)  
CB (B)  
BA (B)  
DB (A)  
BB (B)  
DD (A)  
LL  
2
3
4
5
6
7
8
9
10  
11  
12  
13  
14  
15  
16  
17  
18  
19  
20  
21  
22  
23  
24  
25  
X
X
X
X
NA  
X
Signal Ground  
Received Line Signal Detector  
Receive Signal Element Timing (DCE Source)  
Received Line Signal Detector  
Transmit Signal Element Timing (DTE Source)  
Transmit Signal Element Timing (DCE Source)  
Clear to Send  
Transmitted Data  
Transmit Signal Element Timing (DCE Source)  
Received Data  
X
X
X
X
X
X
X
X
X
Receive Signal Element Timing (DCE Source)  
Local Loopback  
X
X
X
X
CA (B)  
CD (A)  
RL  
CC (B)  
CD (B)  
DA (A)  
Request to Send  
Data Terminal Ready  
Remote Loopback  
Data Set Ready  
X
Data Terminal Ready  
Transmit Signal Element Timing (DTE Source)  
----------  
X
X
Figure 3 – 9 RS530 Link Pinouts  
The connecting cable must be a shielded cable.  
Circuits which are paired (contain an (A) and (B) reference) should be connected to twisted pairs  
within the connecting cable.  
36  
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Link Interfaces Reference  
V.35 Link Pinouts  
1
13  
25  
14  
DB25 Female DTE  
DB25  
Contact  
Number  
1
M.34  
Contact  
Number  
A
CCITT  
Circuit  
Number  
Direction  
To From  
DCE DCE  
NA  
Circuit  
Name  
Protective Ground  
----------  
2
3
----------  
4
C
105  
Request to Send  
X
5
----------  
6
7
8
9
E
B
F
P
S
R
T
107  
102  
109  
103  
103  
104  
104  
Data Set Ready  
Signal Ground  
Data Channel Received Line Signal Detector  
Transmitted Data (A)  
Transmitted Data (B)  
Received Data (A)  
X
NA  
X
X
X
X
X
10  
11  
12  
13  
14  
15  
16  
17  
18  
19  
20  
21  
22  
23  
24  
25  
Received Data (B)  
----------  
V
X
115  
115  
Receiver Signal Element Timing (A)  
----------  
Receiver Signal Element Timing (B)  
----------  
X
X
U
W
H
113  
113  
108.2  
141  
125  
114  
Transmitter Signal Element Timing (A) DTE  
Transmitter Signal Element Timing (B) DTE  
Data Terminal Ready  
Local Loopback  
X
X
X
X
X
X
J
Y
Calling Indicator  
Transmitter Signal Element Timing (A)  
----------  
a
114  
Transmitter Signal Element Timing (B)  
X
Figure 3 - 10 V.35 Link Pin Outs  
The connecting cable must be a shielded cable.  
Circuits which are paired (contain an (A) and (B) reference) should be connected to twisted pairs  
within the connecting cable.  
NOTE For U.K. Approval:  
The connecting cable should be manufactured from Belden Cable, or a cable with equivalent specifications.  
One end must be terminated in a male 34 pin X.21 bis connector as defined in ISO-2593 1984. The other  
end must be terminated in a male 25 pin X.21 bis connector as defined in ISO-2110 1989. The cable may be  
any length between 0 and 5M.  
37  
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Link Interfaces Reference  
RS232 Null-Modem Cable Configuration  
DB25 M ALE  
DB25 M ALE  
1
2
Shield  
Shield  
1
3
R eceived D ata  
Transmitted D ata  
3
2
Transmitted D ata  
D ata Set R eady  
R eceived D ata  
4
6
6
4
R equest To Send  
D ata Set R eady  
R equest To Send  
R eceived Line Signal D etector (C D )  
20 D TE R eady  
8
7
7
8
Signal Ground  
Signal Ground  
D TE R eady  
R eceived Line Signal D etector (C D )  
20  
R eceiver Tim ing D C E Source 17  
15 Transm it Tim ing D C E Source  
Transm it Tim ing D C E Source  
17 R eceiver Tim ing D C E Source  
15  
Transm it Tim ing D TE Source  
24 Transm it Tim ing D TE Source  
24  
Figure 3 - 11 RS232 Null-Modem Cable  
The connecting cable must be a shielded cable.  
This cable is needed when it is necessary to connect two units back-to-back and a set of  
modems is not available. Note that this cable specifies DB25 connectors on each end to allow  
direct connection to the link interface connector on each unit.  
The link speed must be defined for each of the two units.  
38  
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Link Interfaces Reference  
V.35 Null-Modem Cable Configuration  
DB25 MALE  
DB25 MALE  
1
9
Protective GND  
Protective GND  
1
Received Data (A)  
11  
Transmitted Data (A)  
Received Data (B)  
Transmitted Data (A)  
10 Transmitted Data (B)  
12  
9
11 Received Data (A)  
Transmitted Data (B)  
12 Received Data (B)  
10  
14  
16  
Receiver Signal Element Timing (A)  
Receiver Signal Element Timing (B)  
18 Transmitter Signal Element Timing (A)  
19 Transmitter Signal Element Timing (B)  
14 Receiver Signal Element Timing (A)  
16 Receiver Signal Element Timing (B)  
23 Transmitter Signal Element Timing (A)  
25 Transmitter Signal Element Timing (B)  
Transmitter Signal Element Timing (A)  
Transmitter Signal Element Timing (B)  
23  
25  
Transmitter Signal Element Timing (A) 18  
Transmitter Signal Element Timing (B)  
19  
Data Channel Received Line Signal Detector (CD)  
20 Data Terminal Ready  
8
Data Channel Received Line Signal Detector (CD)  
Signal Ground  
8
7
4
20  
Data Terminal Ready  
7
6
Signal Ground  
Data Set Ready  
Request to Send  
6
Data Set Ready  
4
Request to Send  
Figure 3 - 12 V.35 Null-Modem Cable  
The connecting cable must be a shielded cable.  
Circuits which are paired (contain an (A) and (B) reference) should be connected to twisted pairs  
within the connecting cable.  
This cable is needed when it is necessary to connect two units back-to-back and a set of  
modems is not available. Note that this cable specifies DB25 connectors on each end to allow  
direct connection to the link interface connector on each unit.  
The link speed must be defined for each of the two units.  
39  
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Link Interfaces Reference  
RS530 Null-Modem Cable Configuration  
DB25 MALE  
DB25 MALE  
1
2
Shield  
Shield  
1
3
Received Data (A)  
Transmitted Data (A)  
Received Data (B)  
Transmitted Data (A)  
Transmitted Data (B)  
DCE Ready (A)  
14 Transmitted Data (B)  
16  
2
3
Received Data (A)  
16 Received Data (B)  
14  
6
4
Request To Send (A)  
19 Request To Send (B)  
Clear To Send (A)  
13 Clear To Send (B)  
DCE Ready (A)  
DCE Ready (B)  
22  
Clear To Send (A)  
Clear To Send (B)  
5
5
13  
6
Request To Send (A)  
4
22 DCE Ready (B)  
20 DTE Ready (A)  
Request To Send (B) 19  
Received Line Signal Detector (A)  
8
Received Line Signal Detector (B)  
10  
DTE Ready (B)  
23  
7
Signal Ground  
7
20  
23  
17  
9
Signal Ground  
DTE Ready (A)  
Received Line Signal Detector (A)  
8
10 Received Line Signal Detector (B)  
15 Transmit Timing (A) DCE Source  
12 Transmit Timing (B) DCE Source  
DTE Ready (B)  
Receiver Timing (A) DCE Source  
Receiver Timing (B) DCE Source  
Transmit Timing (A) DTE Source  
Transmit Timing (B) DTE Source  
Transmit Timing (A) DTE Source  
Transmit Timing (B) DTE Source  
Local Loopback  
24  
11  
24  
11  
18  
18 Local Loopback  
Remote Loopback  
21  
21  
15  
12  
25  
Remote Loopback  
Receiver Timing (A) DCE Source  
Receiver Timing (B) DCE Source  
Transmit Timing (A) DCE Source  
Transmit Timing (B) DCE Source  
17  
9
25 Test Mode  
Test Mode  
Figure 3 – 13 RS530 Null-Modem Cable  
The connecting cable must be a shielded cable.  
Circuits which are paired (contain an (A) and (B) reference) should be connected to twisted pairs  
within the connecting cable.  
This cable is needed when it is necessary to connect two units back-to-back and a set of  
modems is not available. Note that this cable specifies DB25 connectors on each end to allow  
direct connection to the link interface connector on each unit.  
The link speed must be defined for each of the two units.  
40  
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Link Interfaces Reference  
RS530 To RS449 Conversion Cable  
DB25 MALE  
DB37 MALE/FEMALE  
2
Transmitted Data (A)  
Transmitted Data (B)  
4
22  
14  
3
Received Data (A)  
6
24  
13  
31  
11  
16  
8
Received Data (B)  
Received Line Signal Detector (A)  
Received Line Signal Detector (B)  
Data Set Ready (A)  
10  
6
22  
4
Data Set Ready (B)  
29  
7
Request to Send (A)  
Request to Send (B)  
19  
5
25  
9
Clear to Send (A)  
Clear to Send (B)  
13  
20  
23  
17  
9
27  
12  
30  
Data Terminal Ready (A)  
Data Terminal Ready (B)  
Receiver Signal Element Timing (DCE Source) (A)  
Receiver Signal Element Timing (DCE Source) (B)  
Transmit Signal Element Timing (DCE Source) (A)  
Transmit Signal Element Timing (DCE Source) (B)  
Transmit Signal Element Timing (DTE Source) (A)  
Transmit Signal Element Timing (DTE Source) (B)  
Signal Ground  
8
26  
5
15  
12  
24  
11  
7
23  
17  
35  
19  
Shield  
1
1
Figure 3 – 14 RS530 to RS449 Conversion Cable  
The connecting cable must be a shielded cable.  
Circuits which are paired (contain an (A) and (B) reference) should be connected to twisted pairs  
within the connecting cable.  
This cable is used to connect an RS530 link to an RS449 device. The cable converts from a  
DB25 connector to a DB37 connector.  
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Link Interfaces Reference  
V.11/X.21 Null-Modem Cable Configuration  
Figure 3 – 15 V.11/X.21 Null-Modem Cable  
The connecting cable must be a shielded cable.  
Circuits which are paired (contain an (A) and (B) reference) should be connected to twisted pairs  
within the connecting cable.  
This cable is needed when it is necessary to connect two units back-to-back and a set of  
modems is not available. Note that this cable specifies DB15 connectors on each end to allow  
direct connection to the link interface connector on each unit. The link speed must be defined  
for each of the two units.  
When using this cable to connect two units back-to-back, a jumper must be installed on  
pinheaders W8 and W9 on one of the V.11/X.27 interface modules. This allows that particular  
module to generate the required timing signals.  
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Link Interfaces Reference  
WAN Link Control-Signal Operation  
CTS flow control is not supported.  
It is assumed that Dial In/Dial Out modes of dial-up operation will be configured externally to the  
bridge/router, i.e. on the attached modem, by setting Originate Only/Answer Only modes. A dataset or  
DSU/CSU can be used for a leased-line operation.  
1) When a call is made to the bridge/router, RI will be asserted by the modem. The bridge/router  
responds by driving DTR and RTS high to signal to the partner’s modem that it is ready to establish  
communications. The bridge/router then waits (for the duration of the CD Wait Time, default 60  
seconds) for the partner’s modem to respond with incoming CD and DSR signals driven high. (With a  
dataset or DSU/CSU, RI is not applicable and the bridge/router will respond when CD is high).  
2) After DTR goes high, if the incoming CD is not detected within the CD Wait Time then DTR and  
RTS are lowered for 5 seconds. This clears the link, hangs up the modem and causes the modem to  
redial in an attempt to establish the link. (This “DTR toggle” polling is continuous when the link is  
inactive. When DTR is low, and RI is subsequently asserted, then the bridge/router immediately  
drives DTR and RTS high and again waits for the duration of CD Wait Time for CD to be asserted).  
NOTE: If the level 2 process times out, DTR toggle will be started.  
3) When incoming CD and DSR signals both go high, then it indicates that the local modem, etc. has  
established communications with the remote modem and that communications may begin.  
4) If the link is up, and CD is subsequently interrupted for a period of 10 seconds, then the bridge/router  
assumes the signal is lost and will display an Alarm. As stated previously, if the level 2 protocols can  
continue to send, they will be allowed to do so. This prevents minor line glitches from taking the link  
down upon the loss of CD.  
5) If the RI signal is asserted while DTR is already high, the CD Wait Timer is restarted. Once the CD  
signal is received by the called modem, the state of the RI signal is unimportant.  
6) In the Conditional Link mode, the secondary link will be inactive by holding DTR and RTS low (the  
modem, etc., will normally be configured to drop the call when DTR and RTS are held low). When  
the secondary link needs to become active, DTR and RTS will be raised and the modem will make the  
call.  
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Appendix A - Event Logs  
The router generates event logs for various functions performed by the bridge/router. All of the event logs are stored in the  
internal event log file, which is accessible through the Network Events menu.  
Certain event logs are classified as alarms because they are deemed to be of higher urgency. Alarm logs are indicated by an  
asterisk (“* ”) at the start of the alarm text and are printed on the ALARM line on the menu system as well as being stored in  
the event log. Alarms are listed in the second part of this appendix.  
All WAN-link-related events include the link number in the event log. All remote site-related events include the remote site  
alias in the event log.  
All LCP events are either link based or remote site based depending on whether frame relay is disabled or enabled.  
Event logs:  
CallerID X callback rejected (not resuming)  
Generated when an incoming ISDN call from the specified CallerID has been identified as a request for  
Callback and has been rejected. The request for Callback was rejected because all available circuits were  
reserved for resuming connections, while the Callback request was for a new connection.  
CallerID X callback rejected (call limit)  
Generated when an incoming ISDN call from the specified CallerID has been identified as a request for  
Callback and has been rejected. The request for Callback was rejected because the CallerID was associated  
with a remote site whose call limit was exceeded.  
CallerID X rejected (not resuming)  
Generated when an incoming ISDN call from the specified CallerID has been rejected. The call was rejected  
because all available circuits were reserved for resuming connections, while the incoming call was for a new  
connection.  
CallerID X rejected (usage limit)  
Generated when an incoming ISDN call from the specified CallerID has been rejected. The call was rejected  
because the CallerID was associated with a remote site whose usage limit was exceeded.  
CallerID X security rejection  
Generated when a call has been rejected for security reasons. CallerID security is enabled and the incoming  
CallID does not match any of the numbers configured for any of the remote sites.  
Capture off  
Generated when link trace capture is turned off.  
Client requested address X. No previous record stored.  
Generated when a DHCP IP address request is received from a client and there is no record of that address in the  
address table.  
44  
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Event Logs  
Completed BACP negotiation with <remote site alias>  
Generated when the Bandwidth Allocation Control Protocol negotiation has been completed with the remote site  
device associated with the stated remote site profile. Once BACP negotiations are complete, the two routers will  
negotiate when required to bring up the second link.  
Completed BCP negotiation with <remote site alias>  
Generated when the Bridging Control Protocol negotiation has been completed with the remote site device  
associated with the stated remote site profile. Once BCP negotiations are complete, IP routing may take  
place between the two routers.  
Completed CCP negotiation with <remote site alias>  
Generated when the Compression Control Protocol negotiation has been completed with the remote site device  
associated with the stated remote site profile. Once CCP negotiations are complete, IP routing may take place  
between the two routers.  
Completed CMCP negotiation with <remote site alias>  
Generated when the Connection Management Control Protocol negotiation has been completed with the  
remote site device associated with the stated remote site profile. Once IPCP negotiations are complete, IP  
routing may take place between the two routers.  
Completed IPCP negotiation with <remote site alias>  
Generated when the Internet Protocol Control Protocol negotiation has been completed with the remote site  
device associated with the stated remote site profile. Once IPCP negotiations are complete, IP routing may  
take place between the two routers.  
Completed IPXCP negotiation with <remote site alias>  
Generated when the Internet Packet Exchange Control Protocol negotiation has been completed with the  
remote site device associated with the stated remote site profile. Once IPXCP negotiations are complete,  
IPX routing may take place between the two routers.  
Configuration restored  
Generated during a warm start when a configuration is successfully restored from non-volatile RAM.  
Connection attempt to <IP address>  
Generated when the bridge/router attempts a Telnet connection. The IP address of the target bridge/router is  
specified.  
DHCPserv_Request: client requested Address <IP address>. No previous record stored.  
A client has requested an IP address from the DHCP server that the server has no record of being reserved; the client  
will not receive an address from this server until the client times out and broadcasts an unreserved address request.  
Usually caused by a client connecting from another network.  
DHCP services – declined. Address <IP address> declined by client, mark it as unavailable.  
Generated when a client declines an address offered by the DHCP service, usually because the client has found from  
some other source that the addess is unavailable.  
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Event Logs  
DHCP services – release. <IP address> released.  
Generated when IP address displayed is released from its assignment to a device and put back in the IP pool for re-  
assignment.  
Error executing: XXXXXX  
Generated when an error is detected loading back a configuration. The invalid command is specified.  
Incorrect password from <IP address>  
Generated when an incorrect password is given for a Telnet connection. The connecting bridge/router’s  
name or IP address is specified. After three incorrect login attempts within ten minutes, an alarm is generated  
(see Security alarms: “Possible intruder”) and any further attempts from that IP address within the next ten  
minutes are rejected.  
Invalid Relay Destination for subnetted network  
Generated when a device attempts to do a network broadcast on a subnetted network.  
IP must be enabled on remote site <remote site id>  
Generated when the Internet Protocol Control Protocol negotiations failed due to the remote site device having the  
IPCP function disabled.  
IPX: Network configuration error from X, network Y.  
Generated when the router and server do not agree on a network number.  
IPX: routing table full  
Generated when the IPX RIP table has been filled. Any new RIP frames received will be discarded.  
IPX: Service table full  
Generated when the IPX SAP table has been filled. Any new SAP frames received will be discarded.  
IPX: X, unknown RIP packet type received  
Generated when the device receives an invalid RIP packet.  
IPX: X, unknown SAP packet type received  
Generated when the device receives an invalid SAP packet.  
IPX: X, demand RIP failed  
Generated when this device reaches the end of the attempts to negotiate demand RIP for the IPXCP  
connection. After demand RIP has failed, the normal RIP and SAP updates will occur.  
LCP X authenticating peer with CHAP  
Generated when this device is using CHAP to authenticate the peer (remote) device.  
LCP X authenticating peer with PAP  
Generated when this device is using PAP to authenticate the peer (remote) device.  
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Event Logs  
LCP X establishing  
Generated when the Link Control Protocol of a PPP link or remote site is establishing between this device  
and the remote site PPP device.  
LCP X no reply to Y Echo-Requests  
Generated just prior to a link going down. The link or remote site has gone down due to no replies to the  
echo request messages sent.  
LCP X operational  
Generated when the Link Control Protocol of a PPP link or remote site has been negotiated and is now  
operational between this device and the remote site PPP device.  
LCP X peer authenticating with CHAP  
Generated when the peer (remote) device is using CHAP to authenticate this device.  
LCP X peer authenticating with PAP  
Generated when the peer (remote) device is using PAP to authenticate this device.  
LCP X received Protocol-Reject for <protocol>  
Generated when the peer (remote) device rejects one of the Network Control Protocols.  
Link X - CSU/DSU Digital Loopback Results [Total: X] [Good: X] [Errors: X]  
Generated after the CSU/DSU link module has completed a digital loopback test.  
Link X - CSU/DSU Remote Loopback Results [Total: X] [Good: X] [Errors: X]  
Generated after the CSU/DSU link module has completed a remote loopback test.  
Link X - CSU/DSU Self Test Results [Total: X] [Good: X] [Errors: X]  
Generated after the CSU/DSU link module has completed a self test.  
Link X CSU/DSU: Connected  
Generated when the CSU/DSU link module has established a connection to the remote partner CSU/DSU.  
Link X CSU/DSU: Initialized  
Generated when the CSU/DSU link module has completed initialization and has established  
communications with the router.  
Link X CSU/DSU: Line ERROR  
Generated when the CSU/DSU link module is in an unknown error state.  
Link X CSU/DSU: Loopback Ended  
Generated after the CSU/DSU link module completes a loopback test.  
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Event Logs  
Link X CSU/DSU: Loopback Started  
Generated when the CSU/DSU link module starts a new loopback test.  
Link X - CSU/DSU out of service  
Generated when the CSU/DSU is in communication with the local telco, but is not connected to the remote  
partner CSU/DSU.  
Link X CSU/DSU: No Signal  
Generated when the CSU/DSU link module cannot establish communications with the local telco.  
Link X CSU/DSU: Reset  
Generated when the router has initiated a reset of the CSU/DSU link module.  
Link X - external loopback results[Total: X] [Good: X] [Errors: X]  
Generated after the CSU/DSU link module has completed an external loopback.  
Link X - CSU/DSU CSU telco loopback started  
Generated when the telco has initiated a CSU loopback to this CSU/DSU link module  
Link X - CSU/DSU CSU telco loopback ended  
Generated when the telco has terminated the CSU loopback to this CSU/DSU link module  
Link X - CSU/DSU DSU telco loopback started  
Generated when the telco has initiated a DSU loopback to this CSU/DSU link module  
Link X - CSU/DSU DSU telco loopback ended  
Generated when the telco has terminated the DSU loopback to this CSU/DSU link module  
Link X - CSU/DSU remote loopback ended - line unconnected  
Generated when the CSU/DSU link module cannot establish a connection to the remote partner CSU/DSU to perform  
a remote loopback test.  
Link X - CSU/DSU remote slave loopback started  
Generated when the remote partner CSU/DSU has initiated a loopback to this CSU/DSU link module  
Link X - CSU/DSU remote slave loopback ended  
Generated when the remote partner CSU/DSU has terminated the loopback to this CSU/DSU link module  
Link X – LMI Error Threshold exceeded.  
Generated when the number of LMI enquiry errors exceeds the user-defined limit.  
Link X X [Total: X] [Good: X] [Errors: X]  
Generated after the CSU/DSU link module has completed a test.  
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Event Logs  
LMI discarding STATUS on link X – Enquiries not started  
Generated when the bridge/router discards a Status message received from the frame relay network on a link  
that the bridge/router has not yet started the Local Management Interface.  
No NCP's open, tearing link down  
Generated when a PPP link does not have a Network Control Protocol operating. This may be due to BCP,  
IPCP, and IPXCP being disabled, or the NCP connection was not negotiated to completion.  
Password accepted from <IP address>  
Generated when a correct password is given for a Telnet connection. The connected Bridge/Router’s name  
or IP address is specified.  
Password timer has expired  
Generated when a bridge/router has issued the password prompt for a Telnet connection and timed out  
waiting for the password to be supplied.  
Refused connection attempt from <remote site alias>  
Generated when a connection attempt to a remote site is refused by that site  
Remote Site <remote site alias> re-establishing due to multilink mismatch  
Generated when multilink negotiated on by one end of the link and off by the other. The value for multilink  
will be toggled on this device and LCP will be re-negotiated.  
Remote Site <remote site alias> starting callback  
Generated when an incoming CallID was matched to a remote site, and that remote site was configured for callback.  
The incoming call will be rejected, and an outgoing callback to the remote site will be attempted.  
Restoring boot DNLDSEG configuration  
Generated upon entering Network Load Mode to initialize specific configuration information required for  
retrieving new code image. Generated upon entering operational after a successful code burn into flash.  
Restoring boot EEPROM configuration  
Generated when restoring values in EEPROM configuration, this occurs when entering a load or operational  
mode.  
Running in BOOT mode  
Generated when the bridge/router is starting in Boot mode. This is the mode for software upgrades. Once  
the software upgrade has been successfully completed, the bridge/router restarts in Operational mode.  
Running in OPERATIONAL mode  
Generated when the bridge/router is starting in Operational mode. This is the mode for normal operations  
of the bridge/router.  
SNMP authentication failure for <IP address>  
Generated when an SNMP authentication failure is detected. The SNMP message source is specified by its  
IP address.  
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Event Logs  
Starting BACP negotiation with <remote site alias>  
Generated when the Bandwidth Allocation Control Protocol negotiation has been initiated with the remote  
site device associated with the stated remote site profile.  
Starting BCP negotiation with <remote site alias>  
Generated when the Bridging Control Protocol negotiation has been initiated with the remote site device  
associated with the stated remote site profile.  
Starting CCP negotiation with <remote site alias>  
Generated when the Compression Control Protocol negotiation has been initiated with the remote site device  
associated with the stated remote site profile.  
Starting CMCP negotiation with <remote site alias>  
Generated when the Connection Management Control Protocol negotiation has been initiated with the  
remote site device associated with the stated remote site profile.  
Starting IPCP negotiation with <remote site alias>  
Generated when the Internet Protocol Control Protocol negotiation has been initiated with the remote site  
device associated with the stated remote site profile.  
Starting IPXCP negotiation with <remote site alias>  
Generated when the Internet Packet Exchange Control Protocol negotiation has been initiated with the  
remote site device associated with the stated remote site profile.  
Station address table has been filled  
Generated when the station address table is filled. This event is not regenerated until the table size drops  
below 3/4 full and then fills again.  
STP disabled  
Generated when STP is disabled.  
STP enabled  
Generated when STP is enabled.  
TFTP: stop putting filename to <IP address>  
The bridge/router has sent the final data packet of a file (filename), but has timed out before receiving the  
final ACK. The session may or may not have succeeded in delivering the entire file.  
TFTP: <IP address> finished getting filename  
The bridge/router has sent the final packet of a file (filename) that a LAN device with IP address displayed  
was getting from the bridge/router.  
TFTP: <IP address> finished putting filename  
The bridge/router has ACK-ed the last packet of a file (filename) that a LAN device with IP address  
displayed was putting onto the bridge/router.  
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Event Logs  
TFTP: <IP address> getting filename  
A LAN device with IP address displayed is getting a file (filename) from the bridge/router.  
TFTP: <IP address> putting filename  
A LAN device with IP address displayed is putting a file (filename) onto the bridge/router.  
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Event Logs  
Alarm Logs:  
* Auto-learning of LMI type on link X unsuccessful  
Generated when the LMI type on a link is not successfully auto-learned.  
* Backup Battery is bad  
The backup battery power for memory backup has dropped below operating level, replace the batteries (see  
Installation and Applications Manual, Appendix D.  
* Bad internal block checksum detected  
Generated when power up diagnostics finds a fault in the internal block of the EEPROM.  
* Call X connected  
Generated when an ISDN call has completed connection and is ready to start B channel communication.  
* Closing remote site X (call limit)  
Generated when the specified number of calls has been exceeded.  
* Closing remote site X (callback failure)  
Generated when the remote site interpreted the call sequence as a callback. However, a callback was not  
completed in the expected time frame.  
* Closing remote site X (frame relay closing)  
Generated due to the frame relay protocol being disabled on the bridge/router.  
* Closing remote site X (force disconnect)  
Generated when the connection to a remote site is being closed due to a force disconnect.  
* Closing remote site X (inactivity)  
Generated when the connection to a remote site is being closed due to an inactivity timeout.  
* Closing remote site X (IP triggered RIP)  
Generated when the connection to a remote site is being closed due to failure of IP triggered RIP.  
* Closing remote site X (IPX demand RIP)  
Generated due to the failure of IPX demand RIP.  
* Closing remote site X (last session)  
Generated due to the termination of the last session.  
* Closing remote site X (link disabled)  
Generated due to the link being disabled by the operator.  
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Event Logs  
* Closing remote site X (no NCPs open)  
Generated when no Network Control Protocols operating.  
* Closing remote site X (nonexistant)  
Generated when remote site being deleted by the operator.  
* Closing remote site X (not enabled)  
Generated when remote site autocall being disabled by the operator.  
* Closing remote site X (PVC change)  
Generated due to the enabling or disabling of PPP encapsulation over frame relay.  
* Closing remote site X (resumption failure)  
Generated due to failure to resume a suspended connection.  
* Closing remote site X (scheduled down)  
Generated due to time-of-day schedule deactivation of the connection.  
* Closing remote site X (suspension timeout)  
Generated due to reaching maximum time that the connection may be suspended.  
* Closing remote site X (usage limit)  
Generated due to reaching usage limit for this 24 hour period.  
* Config. erase failed  
Generated when, during a software update, the device configuration is not erased from the non-volatile  
memory within the time limit. Possible hardware failt.  
* Configuration saved  
Generated when the save configuration option has been activated.  
* Configuration too large to be saved  
Generated when the bridge/router attempts to save a configuration that does not fit in the reserved area of  
non-volatile RAM.  
* Connection to LAN X failed, trying ...  
Generated when failure of the LAN interface external loopback test is detected.  
*Count overflow. Reset to history size.  
Generated when the number of events since the event log was cleared exceeds the counter capacity (32,768). Event  
numbers will start over again from 1.  
* DHCP server – out of addresses in IP pool  
Generated when the last address from the DHCP IP Address pool has been assigned to a device.  
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Event Logs  
* Download aborted – Incomplete file  
Generated when a TFTP download is abortet before the file transfer is complete  
* Download aborted – Invalid FCS  
Generated when there is a checksum failure after a file download.  
* Download aborted – Incompatible boot code  
Generated when the operating code file downloaded is incopatible with the boot code in this device. The updated  
boot code software must be loaded before the operating code can be updated.  
* Download aborted – Incompatible software  
Generated when the software downloaded is incompatible with this device  
* Download configuration too large  
The configuration file that is being downloaded will not fit in the memory of this router  
* E-mail server added to firewall  
The IP address of the E-mail server added to the table of services available through the firewall.  
* E-mail server removed from firewall  
The IP address of the E-mail server removed from the table of services available through the firewall.  
* Erasing config. block: starting  
Generated as a notification that the configuration of this device is being erased from non-volatile memory prior to  
loading a software update.  
* Error loading configuration  
Generated during a warm start when an error is detected while restoring a configuration from non-volatile  
RAM.  
* Feature upgrade failure, try again  
Generated when the device detects a checksum error for the feature upgrade block.  
* File copy failed: file crc: X, verify crc: X  
Generated when performing a code upgrade and the calculated CRC was found to be different from the  
transferred CRC (flash.fcs) value.  
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Event Logs  
* FTP server added to firewall  
The IP address of the FTP server added to the table of services available through the firewall.  
* FTP server removed from firewall  
The IP address of the FTP server removed from the table of services available through the firewall.  
* Gopher server added to firewall  
The IP address of the Gopher server added to the table of services available through the firewall.  
* Gopher server removed from firewall  
The IP address of the Gopher server removed from the table of services available through the firewall.  
* IP message received from self  
Generated when the bridge/router receives an IP frame with the same source address as itself. This may be  
caused by three situations: the network has a loop, another device on this network has the same IP address as  
this bridge/router, or another device on this network is spoofing IP using the same IP address as this  
bridge/router.  
* IP protocol parameters uninitialized  
Generated when IP protocol communications fail for a remote site configured for frame relay because an IP  
address does not exist.  
* ISDN BRI interface deactivated  
Generated when the ISDN link module has lost a physical connection to the NT-1.  
* ISDN BRI interface activated  
Generated when the ISDN link module has established a physical connection to the NT-1.  
* LAN connection established  
Generated on startup when integrity of the LAN interface has been successfully verified by the external  
loopback test.  
* Link X attached to remote site <remote site alias>  
Generated when a PPP ISDN call is attached to a remote site.  
* Link X attached to remote site <remote site alias>  
Generated when Link X has been identified as a connection to the specified remote site.  
* Link X busy  
Generated when a call was attempted on the link while it already had a call in progress. This may also occur  
if the link was not activated at the time of the call.  
* Link X control signals down  
Generated when a high-to-low transition is detected on the CD control signal. Note that there is no  
associated event for the low-to-high transition.  
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Event Logs  
* Link X Connected  
Generated when and end-to-end ISDN call has been established.  
* Link X connection rejected  
Generated when Link X connection is being terminated as it could not be attached to a remote site. This  
may be due to usage limits or suspension resumptions.  
* Link X - CSU/DSU not responding, Power Cycle Device.  
Generated when the router cannot establish communications with the CSU/DSU link module. The power  
must be cycled on the router to cause a restart of the CSU/DSU module.  
* Link X Disconnect: Y  
Generated when the disconnect of an ISDN call is completed. This event is generated on both sides of the  
ISDN call. The cause will be one of the causes as specified in the CCITT Recommendation Q.931. Causes  
of “normal call clearing”, “User busy”, and “Number changed” are printed in words, all other are numeric.  
Code  
001  
002  
003  
004  
006  
007  
008  
009  
010  
011  
016  
017  
018  
019  
020  
021  
022  
023  
024  
025  
026  
027  
028  
029  
030  
031  
Description  
Unallocated/unassigned number  
No route to specified transit network  
No route to destination  
Channel unacceptable  
Channel unacceptable  
Call awarded and being delivered in an established channel  
Prefix 0 dialed but not allowed  
Prefix 1 dialed but not allowed  
Prefix 1 dialed but not required  
More digits received than allowed, call is proceeding  
Normal call clearing  
User busy  
No user responding  
No answer from user  
Circuit operational  
Call rejected  
Number changed  
Reverse charging rejected  
Call suspended  
Call resumed  
Non-selected user clearing  
Destination out of order  
Invalid number format  
Facility rejected  
Response to STATUS INQUIRY  
Normal, unspecified  
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Event Logs  
Code  
033  
034  
035  
036  
037  
038  
039  
040  
041  
042  
043  
044  
045  
046  
047  
049  
050  
051  
052  
053  
054  
055  
056  
057  
058  
063  
065  
066  
067  
068  
069  
070  
079  
081  
082  
083  
084  
085  
086  
087  
088  
089  
090  
091  
092  
093  
095  
096  
097  
098  
099  
100  
101  
102  
111  
127  
Description  
Circuit out of order  
No circuit/channel available  
Destination unattainable  
Out of order  
Degraded service  
Network out of order  
Transit delay range cannot be achieved  
Throughput range cannot be achieved  
Temporary failure  
Switching equipment congestion  
Access information discarded  
Requested circuit/channel not available  
Preemption  
Precedence call blocked  
Resources unavailable, unspecified  
Quality of service unavailable  
Requested facility not subscribed  
Reverse charging not allowed  
Outgoing calls barred  
Outgoing calls barred within CUG  
Incoming calls barred  
Incoming calls barred within CUG  
Call waiting not subscribed  
Bearer capability not authorized  
Bearer capability not presently available  
Service or option not available, unspecified  
Bearer capability not implemented  
Channel type not implemented  
Transit network selection not implemented  
Message not implemented  
Requested facility not implemented  
Only restricted digital information bearer capability is available  
Service or option not implemented, unspecified  
Invalid call reference value  
Identified channel does not exist  
A suspended call exists, but this call identity does not  
Call identity in use  
No call suspended  
Call having the requested call identity has been cleared  
Destination address not member of CUG  
Incompatible destination  
Non-existent abbreviated address entry  
Destination address missing  
Invalid transit network selection  
Invalid facility parameter  
Mandatory information element is missing  
Invalid message, unspecified  
Mandatory information element is missing  
Message type non-existent or not implemented  
Message not compatible with call state or type non-existent or not implemented  
Information element non-existent or not implemented  
Invalid information element contents  
Message not compatible with call state  
Recovery on timer expiry  
Protocol error - unspecified  
Interworking - unspecified  
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Event Logs  
* Link X, DLCI Y attached to remote site <remote site alias>  
Generated for frame relay applications when a connection has been made for the DLCI associated with the remote  
site alias.  
* Link X down  
Generated when a WAN link goes down.  
* Link X down to <remote site alias>  
Generated when a PPP ISDN call to a remote site is dropped.  
* Link X down to <remote site alias>  
Generated when a WAN link connection to the specified remote site goes down.  
* Link X Incoming Data Call [to/from] [callingDN/calledDN]  
Generated when an incoming data call is presented from ISDN and the caller directory number is not  
presented.  
* Link X – LMI Error Threshold exceeded  
Generated when the defined error threshold has been exceeded on the specified link.  
* Link not available for remote site <remote site alias>  
The link associated with this remote site is already in use.  
*Link not configured for frame relay on remote site <remote site alias>  
The link that has been assigned to this remote site is not configured for frame relay.  
*Link not configured for leased line on remote site <remote site alias>  
The link that has been assigned to this remote site is not configured for leased line operation.  
* Link X Outgoing Data Call to [DN]  
Generated when a data call is outgoing to the dialing network.  
* Link X Registered  
Generated when the link has registered with the network. This alarm is only applicable for switchtype which  
required SPID entry. No incoming or outgoing calls are possible on the link until the link has registered.  
* Link X Registration Failed: Y  
Generated when the registration of this link with the network has failed. Repeated failures may indicate that  
the entered SPID value is incorrect.  
* Link X up  
Generated when a WAN link comes up.  
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Event Logs  
* Link X up at Y baud  
Generated when frame relay link is established.  
* Link X up to <remote site alias>  
Generated when a WAN link connection to the specified remote site comes up.  
* Local DNS server added to firewall  
The IP address of the Local DNS server added to the table of services available through the firewall.  
* Local DNS server removed from firewall  
The IP address of the Local DNS server removed from the table of services available through the firewall.  
* Main Battery is bad  
The main battery power for memory backup has dropped below operating level, replace the batteries (see Installation  
and Applications Manual, Appendix D.  
* Max number of NAT UDP entries reached  
Generated when more than the allowed maximum number of UDP entries has been attempted. This feature is in  
place to prevent denial of service attacks.  
* NAT exported services added to firewall  
The IP address of the NAT exported services added to the table of services available through the firewall.  
* NAT exported services removed from firewall  
The IP address of the NAT exported services removed from the table of services available through the firewall.  
* NAT table full  
Generated when no more ports are available for Network Address Translation.  
* No available remote site for learned DLCI  
Generated when, during Frame Relay Auto-learning, the remote site table is filled, no space is available to create  
another entry. The user must manually edit the table to remove some remote site profiles before another entry can be  
made.  
* No available remote site for leased line X  
Generated when attempting to set up a default leased line remote site and the remote site table is filled, no space is  
available to create another entry. The user must manually edit the table to remove some remote site profiles before  
another entry can be made.  
* No saved configuration, using default  
Generated during a cold start when no saved configuration is available.  
* No ISDN call configured for remote site <remote site alias>  
The remote site selected does not have the ISDN parameters configured properly to make a connection – re-edit the  
site profile.  
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Event Logs  
* No ISDN line available for remote site <remote site alias>  
All ISDN lines are currently in use; none are available for the new connection requested. May be generated when  
CMCP is enabled and more ISDN calls are attempted than there are available ISDN lines.  
* No ISDN resource available for remote site <remote site alias>  
All ISDN lines are currently in use; none are available for the new connection requested. May be generated when  
CMCP is enabled and more ISDN calls are attempted than there are available ISDN lines.  
* No link number configured for remote site <remote site alias>  
A remote site with a frame relay or leased line connection must have a link number assigned to it. If this messaage  
appears, re-edit the remote site connection set-up to assign a link.  
* No remote site available  
The remote site table is full, there is no space available to create a remote site profile for this ISDN number or IP  
address. The user must manually edit the table to remove some remote site profiles before another entry can be made.  
* Old download method! Load in \”*.all\” file  
Generated when an attempt is made to load a *.fcs or *.lda format program file into hardware which will only accept  
*.all format code.  
* Old format configuration, using default  
Generated when the saved configuration does not match the expected correct revision number. The old  
configuration formats will not be used.  
* Outgoing call number X too long  
Generated when an outgoing call has been attempted in which the number of dialed digits exceeds the limit.  
* POP2/POP3 server added to firewall  
The IP address of the POP2/POP3 server added to the table of services available through the firewall.  
* POP2/POP3 server removed from firewall  
The IP address of the POP2/POP3 server removed from the table of services available through the firewall.  
* Remote Site <remote site alias> already active  
Generated when a connection is attempted to a remote site that is busy.  
* Remote Site <remote site alias> already connected  
Generated when a connection is attempted to a site that is already connected to this router.  
* Remote site <remote site alias> connected  
Generated when the specified remote site has been connected for connection management.  
* Remote site <remote site alias> down  
Generated when the remote site configured for frame relay has gone down due to failure of security tests.  
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Event Logs  
* Remote site <remote site alias> frame relay closing  
Generated when frame relay is diabled on the link to the specified remote site.  
* Remote site <remote site alias> resumed  
Generated when the connection to the specified remote site has been resumed.  
* Remote Site <remote site alias> still closing  
Generated when a connection is attempted to a remote site whose link is still in the process of being disconnected.  
* Remote site <remote site alias> suspended  
Generated when the connection to the specified remote site has been suspended.  
* Remote site <remote site alias> terminated  
Generated when the connection to the specified remote site has been terminated for connection management.  
* Results of IPCP negotiation are incompatible  
Generated when IPCP negotiations with a remote site PPP router result in a incompatible IP configuration.  
The remote site is then disconnected.  
* Running in System Load mode  
Generated when entering System Load Mode in preparation for a download of code to be burned into flash.  
* Service added to firewall  
The IP address of the Service added to the table of services available through the firewall.  
* Service removed from firewall  
The IP address of the Service removed from the table of services available through the firewall.  
* Telnet server removed from firewall  
The IP address of the Telnet server removed from the table of services available through the firewall.  
* Telnet server added to firewall  
The IP address of the Telnet server added to the table of services available through the firewall.  
* TFTP: Abort. ACK retry exceeded  
Aborted a TFTP session because the bridge/router did not receive a new data packet within the TFTP “T1”  
times “N2” interval.  
* TFTP: Abort. ACK timeout  
Aborted a TFTP session because the bridge/router did not receive an ACK for the last data packet it sent  
within the TFTP “T1” times “N2” interval.  
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Event Logs  
* TFTP: Abort. Error (#) received  
Aborted a TFTP session because of the reception of a TFTP error message from the connected device. The  
errors are: 0 - not defined, 1 - file not found, 2 - access violation, 3 - disk full or allocation exceeded, 4 -  
illegal TFTP operation, 5 - unknown transfer ID, 6 - file already exists, 7 - no such user.  
* Unable to route!! UDP failure  
Generated when the device tried to open an already open UDP channel, causing IP routing to fail.  
* Unable to bind UDP Boot P client port  
Generated as a result of a n internal device error. Try resetting the device. If this is unsuccessful, contact a  
service representative.  
* Unable to bind UDP Boot P server port  
Generated as a result of a n internal device error. Try resetting the device. If this is unsuccessful, contact a service  
representative.  
* Unable to bind UDP DHCP server port  
Generated as a result of a n internal device error. Try resetting the device. If this is unsuccessful, contact a  
service representative.  
* Unable to allocate memory for DHCP server save  
Generated when the memory on this device has become too fragmented to find a contiguous block of memory large  
enough for the DHCP server tables. Reset the device to defragment memory.  
* Unknown call type on remote site X  
The attempted call is not an ISDN, Frame Relay or PPP leased line call. Possible cause is a remote site profile being  
deleted while a connection attempt is being made.  
* WWW (HTTP) server removed from firewall  
The IP address of the WWW (HTTP) server removed from the table of services available through the firewall.  
* WWW (HTTP) server added to firewall  
The IP address of the Telnet WWW (HTTP) added to the table of services available through the firewall.  
* X count overflow. Reset to history size  
Generated when the number of items logged exceeds the space available. X = “ALARM” or “EVENT”  
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Event Logs  
PPP Security Logs:  
CHAP authentication failure so terminate link.  
Generated when the CHAP authentication sent by this router in response to a request from a remote site is  
rejected.  
CHAP failed for <remote site alias>  
Generated when the remote site router failed a CHAP authentication request from this router. The remote  
site name is displayed if known.  
CHAP failed to complete  
Generated when the remote site router sent a CHAP challenge and this router sent a response, but no  
further information was received from the remote site router.  
CHAP login refused by <remote site alias>  
Generated when the remote site router sent a CHAP challenge and this router sent a response, and the  
remote site router refused the connection. The remote site name is displayed if know.  
Link X refused to authenticate  
Generated when the remote site router refused to do authentication.  
PAP authentication failure for user Y  
Generated when the PAP password sent by this router in reply to the remote site router PAP password request is  
rejected.  
PAP failed for <remote site alias>  
Generated when the remote site router failed a PAP authentication request from this router. The remote site  
name is displayed if know.  
PAP X failed to complete (Y)  
Generated when the remote site router sent a PAP password request and this router sent the PAP password  
in reply, but no further information was received from the remote site router.  
PAP X peer failed to authenticate  
Generated when the remote site router did not respond to a request to authenticate.  
Possible intruder <IP address> exceeded password attempts limit  
A telnet connection attempt from the displayed IP address to gain access to the router management menus has tried  
to login over three times with incorrect passwords within the past ten minutes. This may be an attempt to gain  
unauthorized access to the management of this router. Any further attempts within the next ten minutes form this IP  
address to gain access will be rejected.  
Remote Site <remote site alias> refused to authenticate  
Generated when the remote router refused to do authentication for the frame relay remote site.  
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Appendix B - Programmable Filtering  
Programmable filtering gives the network manager the ability to control under what conditions Ethernet frames are forwarded  
across bridge or bridge/router ports. There are many reasons why this might need to be accomplished, some of which are  
security, protocol discrimination, bandwidth conservation, and general restrictions.  
To reach a specific filtering goal, there is usually more than one possible filter expression that may be used. This of course is  
dependent on the specific filtering requirement, and how flexible the filter should be.  
The following pages describe how programmable filters may be used in typical applications. Although this is only a small  
sampling of the many possibilities, a cross-section of use of filters is presented.  
MAC Address Filtering  
Security  
The need for security has become increasingly important in Local Area Networking, and with the use of programmable filters,  
security may be easily and effectively implemented across segment boundaries. By defining a programmable filter, the  
network manager may control what traffic is allowed between LAN segments, thereby controlling the security of resources by  
preventing unauthorized user access.  
The router provides three built-in functions – in addition to defined programmable masks – to control the access to  
resources. The first function is “Filter if Source”; the second is “Filter if Destination.” The third function allows you to  
change the filter operation from “positive” to “negative.” Positive filter operation causes the specified MAC addresses to be  
filtered according to the entered method. Negative filter operation causes the specified MAC addresses to be forwarded  
according to the entered method.  
You may easily prevent any station on one segment from accessing a specific resource on the other segment; for this,  
“positive” filtering and the use of “Filter if Destination” would be appropriate. If you want to disallow a specific station from  
accessing any service, “Filter if Source” could be used.  
You may easily prevent stations on one segment from accessing all but a specific resource on the other segment; for this,  
“negative” filtering and the use of “Forward if Destination” would be appropriate. If you want to disallow all but a specific  
station from accessing any service on the other segment, the use of “Forward if Source” could be used.  
Example cases are found on the following pages.  
TCP/IP, XNS, and Novell Netware frame formats, as well as some common Ethernet type codes, are found by the back  
cover.  
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Programmable Filtering  
Security—“Filter if Destination”  
Filter if Destination is a function that allows you to filter an Ethernet frame based on the destination of its address.  
If the destination address equals the address that the Filter if Destination function has been applied to, the frame is  
filtered.  
Example:  
Assume that a host Computer is located on LAN segment 2 located on a partner bridge/router with an Ethernet  
address of:  
00-00-01-02-03-04  
(host Ethernet address)  
Since each station on a LAN has a unique Ethernet address, this address uniquely identifies this host computer.  
To prevent LAN users located on segment 1, located on the local bridge/router, from accessing this host system,  
follow the instructions below:  
1
From the MAIN MENU of the console of the local bridge/router, enter a 1.  
(Enter a “=“ from any menu to go back to the MAIN MENU.)  
This will place you at the CONFIGURATION MENU, where access to the filtering menu is obtained.  
2
3
4
5
From the CONFIGURATION MENU, enter an 8.  
This will place you at the FILTER SET-UP MENU, where access to the individual filtering menus is  
obtained.  
From the FILTER SET-UP MENU, enter a 1.  
This will place you at the MAC ADDRESS FILTERS MENU, where access to the MAC Address filters is  
obtained.  
From the MAC ADDRESS FILTERS MENU, make sure that Filter Operation is currently set to positive.”  
This will cause the MAC Address Filters specified to be used for filtering frames with the specified MAC  
addresses.  
From the MAC ADDRESS FILTERS MENU, enter a 1.  
This will place you at the first EDIT MAC ADDRESS FILTER MENU screen.  
At the prompt enter the MAC address for which you want to specify the filter.  
6
7
Enter the 12-digit Ethernet address of the host system in the following format:  
000001020304 (enter a Return)  
The edit screen will fill in the information that the table knows about this address. For this example, let us  
assume that it knows that the address is “present” and located on the LAN of the partner bridge/router.  
Enter a 4 to Enable the “Filter if Destination ” parameter. The screen will be updated with the new  
information.  
At this point, the address is added to the permanent filter table of the local LAN. This entry, therefore, will not be  
subject to the aging timer, and will remain active until it is removed from the permanent entry table.  
When a frame of information is seen on the local LAN that contains the address of the host system in the destination  
field of the frame, the bridge/router will not forward it, effectively preventing any access to this host from the local  
LAN.  
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Programmable Filtering  
Security—“Filter if Source”  
Filter if Source is a function that allows you to filter an Ethernet frame if the source address of the frame equals the  
address that the Filter if Source function has been applied to.  
Example:  
Assume that a Personal Computer is located on segment 1 on the local bridge/router. This station is a community  
station that various departments may use for general processing. However, this station may only access those services  
that exist on its local segment, and it must be restricted from accessing any services on remote LANs. This can be  
easily accomplished with a “Filter if Source.”  
The Ethernet Address for this Personal Computer is: 01-02-03-04-05-06  
Again, this address uniquely identifies this computer station.  
To configure the bridge/router to ensure that this station is unable to access facilities on a remote LAN segment,  
follow the instructions below:  
1
From the MAIN MENU of the console of the local bridge/router, enter a 1.  
(Enter a “=“ from any menu to go back to the MAIN MENU.)  
This will place you at the CONFIGURATION MENU, where access to the filtering menu is obtained.  
2
3
4
From the CONFIGURATION MENU, enter an 8.  
This will place you at the FILTER SET-UP MENU, where access to the individual filtering menus is  
obtained.  
From the FILTER SET-UP MENU, enter a 1.  
This will place you at the MAC ADDRESS FILTERS MENU, where access to the MAC Address filters is  
obtained.  
From the MAC ADDRESS FILTERS MENU, make sure that the Filter Operation is currently set to  
“positive.”  
This will cause the MAC Address Filters specified to be used for filtering frames with the specified MAC  
addresses.  
5
6
From the MAC ADDRESS FILTERS MENU, enter a 1.  
This will place you at the first EDIT MAC ADDRESS FILTER MENU screen.  
At the prompt enter the MAC address for which you want to specify the filter.  
Enter the 12-digit Ethernet address of the Personal Computer system in the following format:  
010203040506 (enter a Return)  
The edit screen will fill in the information that the table knows about this address. For this example, let us  
assume that it knows that the address status is [not present] and is of [unknown] location.  
In this example, the bridge/router is not aware of this station as of yet. The station has probably not been  
active for the bridge/router to “learn” any information about it.  
Therefore, you will have to tell the bridge/router a little bit more about the station.  
7
Enter a 2 to enter the location of the station.  
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Programmable Filtering  
8
9
The bridge/router will prompt you for the LAN that the station is located on; enter the name of the partner  
bridge/router LAN (LAN345678, for example).  
Note that the Status of the address is marked as [present], the location is updated to LAN345678 and the  
Permanent entry is [enabled].  
Enter a 3 to [enable] the “Filter if Source ” parameter. The edit screen will be updated to show the new  
information.  
At this point, the address is added to the permanent filter table of the local LAN. This entry, therefore, will not be  
subject to the aging timer, and will remain active until it is removed from the permanent entry table.  
When a frame of information is seen on the local LAN that contains the address of the Personal Computer in the  
source field of the frame, the bridge/router will not forward it, effectively preventing any access from the PC to  
remote LANs.  
Most programmable filtering options may be used for security purposes. The examples above are specific instances where the  
two “Filter if” functions may be used.  
Security—“Forward if Destination”  
Forward if Destination is a function that allows you to forward an Ethernet frame based on the destination of its  
address and filter all other frames. If the destination address equals the address that the Forward if Destination  
function has been applied to, the frame is forwarded.  
Example:  
Assume that a host Computer is located on LAN segment 2 located on a partner bridge/router with an Ethernet  
address of:  
00-00-01-02-03-04  
(host Ethernet address)  
Since each station on a LAN has a unique Ethernet address, this address uniquely identifies this host computer.  
To prevent LAN users located on segment 1, located on the local bridge/router, from accessing any only this host  
system and no other systems, follow the instructions below:  
1
From the MAIN MENU of the console of the local bridge/router, enter a 1.  
(Enter a “=“ from any menu to go back to the MAIN MENU.)  
This will place you at the CONFIGURATION MENU, where access to the filtering menu is obtained.  
2
3
From the CONFIGURATION MENU, enter an 8.  
This will place you at the FILTER SET-UP MENU, where access to the individual filtering menus is  
obtained.  
From the FILTER SET-UP MENU, enter a 1.  
This will place you at the MAC ADDRESS FILTERS MENU, where access to the MAC Address filters is  
obtained.  
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Programmable Filtering  
4
5
6
7
From the MAC ADDRESS FILTERS MENU, make sure that the Filter Operation is currently set to  
“negative.”  
This will cause the MAC Address Filters specified to be used for forwarding frames with the specified MAC  
addresses.  
From the MAC ADDRESS FILTERS MENU, enter a 1.  
This will place you at the first EDIT MAC ADDRESS FILTER MENU screen.  
At the prompt enter the MAC address for which you want to specify the filter.  
Enter the 12-digit Ethernet address of the host system in the following format:  
000001020304 (enter a Return)  
The edit screen will fill in the information that the table knows about this address. For this example, let us  
assume that it knows that the address is “present” and located on the LAN of the partner bridge/router.  
Enter a 4 to Enable the “Forward if Destination” parameter. The edit screen will be updated to show the  
new information.  
At this point, the address is added to the permanent filter table of the local LAN. This entry, therefore, will not be  
subject to the aging timer, and will remain active until it is removed from the permanent entry table.  
When a frame of information is seen on the local LAN that contains the address of the host system in the destination  
field of the frame, the bridge/router will forward it. All other frames seen on the local LAN that are destined for the  
remote LAN will be filtered.  
Security—“Forward if Source”  
Forward if Source is a function that allows you to forward an Ethernet frame if the source address of the frame  
equals the address that the Forward if Source function has been applied to.  
Example:  
Assume that a Personal Computer is located on segment 1 on the local bridge/router. This station belongs to the  
head of Marketing. This station requires access to all the services that exist on the remote LAN but no other station  
on the local LAN is allowed to access the remote LAN. This can be easily accomplished with a “Forward if Source.”  
The Ethernet Address for this Personal Computer is: 01-02-03-04-05-06  
Again, this address uniquely identifies this computer station.  
To configure the bridge/router to ensure that only this station is able to access facilities on a remote LAN segment,  
follow the instructions below:  
1
From the MAIN MENU of the console of the local bridge/router, enter a 1.  
(Enter a “=“ from any menu to go back to the MAIN MENU.)  
This will place you at the CONFIGURATION MENU, where access to the filtering menu is obtained.  
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Programmable Filtering  
2
3
4
From the CONFIGURATION MENU, enter an 8.  
This will place you at the FILTER SET-UP MENU, where access to the individual filtering menus is  
obtained.  
From the FILTER SET-UP MENU, enter a 1.  
This will place you at the MAC ADDRESS FILTERS MENU, where access to the MAC Address filters is  
obtained.  
From the MAC ADDRESS FILTERS MENU, make sure that the Filter Operation is currently set to  
“negative.”  
This will cause the MAC Address Filters specified to be used for forwarding frames with the specified MAC  
addresses.  
5
6
At this menu, enter a 1.  
This will place you at the first EDIT MAC ADDRESS FILTER MENU screen.  
At the prompt enter the MAC address for which you want to specify the filter.  
Enter the 12-digit Ethernet address of the Personal Computer system in the following format:  
010203040506 (enter a Return)  
The edit screen will fill in the information that the table knows about this address. For this example, let us  
assume that it knows that the address status is [not present] and is of [unknown] location.  
In this example, the bridge/router is not aware of this station yet. The station has probably not been active  
for the bridge/router to “learn” any information about it.  
Therefore, you will have to tell the bridge/router a little bit more about the station.  
7
8
Enter a 2 to enter the location of the station.  
The bridge/router will prompt you for the LAN that the station is located on; enter the name of this  
bridge/router’s LAN (LAN456789 for example).  
Note that the Status of the address is marked as [present], the location is updated to LAN456789 and the  
Permanent entry is [enabled].  
9
Enter a 3 to [enable] the “Forward if Source” parameter. The edit screen will be updated to show the new  
information.  
At this point, the address is added to the permanent filter table of the local LAN. This entry, therefore, will not be  
subject to the aging timer, and will remain active until it is removed from the permanent entry table.  
When a frame of information is seen on the local LAN that contains the address of the Personal Computer in the  
source field of the frame, the bridge/router will forward it. All other frames seen on the local LAN that are destined  
for the remote LAN will be filtered.  
Most programmable filtering options may be used for security purposes. The examples above are specific instances where the  
two “Forward if” functions may be used. Filter masks are presented in subsequent pages of this section.  
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Programmable Filtering  
Pattern Filter Operators  
The following operators are used in creating Pattern filters and will be discussed further in the following pages. For  
additional information refer to the octet locations diagrams at the back of this manual. Each octet location may contain a  
HEX value.  
-
offset  
OR  
Used in pattern filters to determine the starting position to start the pattern checking.  
Example:  
12-80  
This filter pattern will match if the packet information starting at  
the 12th octet equals the 80 of the filter pattern.  
|
Used in combination filters when one or the other conditions must be met.  
Example:  
10-20|12-80  
This filter pattern will match if the packet information starting at  
the 10th octet equals the 20 of the filter pattern or if the packet  
information starting at the 12th octet equals the 80 of the filter  
pattern.  
&
AND  
Used in combination filters when one and the other conditions must be met.  
Example:  
10-20&12-80  
This filter pattern will match if the packet information starting at  
the 10th octet equals the 20 of the filter pattern and the packet  
information starting at the 12th octet equals the 80 of the filter  
pattern.  
~
NOT  
Used in pattern filters to indicate that all packets not matching the defined pattern will be filtered.  
Example:  
~12-80  
This filter pattern will match if the packet information starting at  
the 12th octet does not equal the 80 of the filter pattern.  
( )  
brackets  
Used in pattern filters to separate portions of filter patterns for specific operators.  
Example: 12-80&(14-24|14-32) This filter pattern will be checked in two operations. First the  
section in brackets will be checked and then the results of the first  
check will be used in the second check using the first portion of  
the filter patter. If the packet information starting at the 14th octet  
equals 24 or 32, and the information at the 12th octet equals 80, the  
filter pattern will match.  
@
Connect  
Used in pattern filters to indicate that the filter will only be active when the remote site connection is  
down. This is only available on the P1730.  
Example:  
@12-80  
This filter pattern will match if the remote site connection is down  
and the packet information starting at the 12th octet equals the 80  
of the filter pattern.  
Bridge Pattern Filtering  
Protocol Discrimination  
Protocol discrimination may be required to prevent or limit the protocols that may traverse a bridged Local Area Network.  
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Programmable Filtering  
In Local Area Networks there may be many different Network and Transport layer protocols that coexist on the same physical  
media. TCP/IP, DECNET, and XNS are just a few of the common protocols in use today. Each of these protocols is  
encapsulated within an Ethernet frame, and therefore is transparent to the normal bridging function. If you would like to  
discriminate against a particular protocol to prevent its use of the bridged LAN facilities, the router provides programmable  
filter masks that may be defined to act on any part of the Ethernet frame.  
In the examples below, several protocol types and combinations are presented to demonstrate the use of programmable filter  
masks to control the protocol traffic between Local Area Network segments. Since there are many possible combinations,  
these examples are only representative of some of them.  
The Bridge Filter Patterns menu is located under the FILTER SET-UP MENU. Within the Bridge Filter Patterns Menu  
there exists a Help function that can be used as a reference during Bridge Filter Pattern creation. This Help function  
includes all of the logical operators that may be applied to the mask expression.  
Protocol Type Field  
Within an Ethernet frame, a protocol field exists at octet 12 and 13. These two octets, or 8-bit bytes, will represent  
the type of higher level protocol that exists in the Ethernet frame. There are more than 100 different protocol types  
that are defined for use within an Ethernet frame. In many networks there will be fewer than 10 that are in use, but  
in many larger networks there may be upwards of 30 or more. This, of course, will depend on the type of equipment  
and the applications that are being used within the Local Area Network.  
Internet Protocol (IP)  
The Internet Protocol (IP) is the most widely used protocol within an Ethernet environment. As a result there may  
be a need to restrict in one form or another this protocol traffic.  
Filter all IP Packets  
To prevent IP traffic from being passed across the bridged network, a mask must be created that represents this  
protocol type. The IP protocol type is 0800H.  
Since the protocol field starts at octet location 12, the necessary filter mask to prevent IP traffic from traversing the  
bridged network is as follows: 12-0800  
The 12 is the offset into the Ethernet frame, the “-” is the argument separator, and the 0800 represents the protocol  
type of IP.  
In this example, whenever a frame is seen on the LAN port, for which this filter mask has been specified, with a  
protocol of type equal to IP, the frame will be filtered.  
Note that when you filter on IP frames, all frames using the IP protocol will also be filtered. This includes TCP,  
UDP, SNMP, etc.  
IP, and no more  
This example performs just the opposite function to the above example. Only IP packets will be allowed to be  
passed across the bridged network.  
For this function there must be a method to prevent all but IP packets from being filtered. For this the NOT (“~”)  
logical operator is used. The NOT operator specifies that the expression has to be FALSE before the frame is  
filtered. In other words, only frames that are NOT equal to the expression will be filtered and discarded.  
To create this mask, the following expression is entered: ~(12-0800)  
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Programmable Filtering  
The parenthesis simply ensures that the NOT operator will apply to the entire expression.  
In this case, whenever a frame is received, the frame will be filtered if the protocol type is NOT equal to 0800 (IP).  
Only one filter pattern may be used that contains the NOT operator.  
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Programmable Filtering  
Transport Control Protocol / Internet Protocol (TCP/IP)  
The previous example showed how to filter all Ethernet frames that contained an IP protocol packet. However, IP is  
used as the Network-layer protocol for more than 40 different Transport-layer protocols, TCP being only one of  
them. Therefore, with the mask that was used as noted in the previous IP example, all Transport layer protocols that  
used IP would also be filtered. This may not be desirable in all cases.  
For this example, the discrimination of the Transport Layer used within an IP packet will be demonstrated. This  
requires an AND function, since we want to filter data that both is IP and contains TCP information.  
Within the IP frame, there is a single octet field that may be used to indicate the protocol of the Transport layer, or  
the protocol of the data in the IP packet. If TCP were the protocol within the IP packet, this octet, or 8-bit byte,  
would be equal to 6.  
The location of this field, remembering that the start of the Ethernet frame is always the base reference, is octet 23.  
Filter only TCP/IP  
To filter only those packets that are TCP/IP, the mask would therefore be: 12-0800&23-06  
The 12-0800 is the IP expression and the 23-06 will represent TCP in an IP frame. The “&” is the logical AND  
operator, so the expression requires that the frame be both an IP and TCP.  
Filter all IP without TCP traffic  
To filter all IP packets that do not contain TCP traffic, the mask would be : 12-0800&~(23-06)  
Filter all except TCP/IP  
To filter all other packets except TCP/IP packets, the mask would be: ~(12-0800&23-06)  
Local Area Transport (LAT)  
The Local Area Transport (LAT) protocol is used exclusively by DEC for terminal access between DEC hosts and  
terminal servers located on an Ethernet network.  
This example is similar to the Internet Protocol example described previously.  
The protocol type field value that is used for LAT frames is equal to 6004.  
Filter all LAT  
Therefore, to filter all LAT frames, the filter mask would be: 12-6004  
Filter all but LAT  
To filter all frames but LAT frames, the filter mask would be: ~(12-6004)  
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Programmable Filtering  
DEC  
DEC uses protocol types 6000 to 600F, and although some are undefined, a simple filter mask can be created to filter  
all DEC traffic.  
Filter all DEC  
The mask to filter all DEC traffic would be: 12-600X  
The X is a variable representing the last four bits (a nibble) of the type. This will effectively filter all Ethernet frames  
that contain a protocol type of 6000 through to 600F. All 16 possible combinations are covered.  
Bandwidth Conservation  
Reducing traffic on each LAN segment is one benefit of the bridging functions of a router. There are several simple  
methods that may be used to provide a further reduction of inter-LAN traffic. The examples that follow present a few very  
simple methods to reduce inter-LAN traffic, without necessarily reducing resource capability.  
Ethernet Broadcasting  
On an Ethernet LAN, any station may broadcast information to all other stations by setting the Ethernet Destination  
address to FF-FF-FF-FF-FF-FF. By configuring the destination address to this setting, it is telling all other stations  
that this is a broadcast message.  
In many situations, stations will abuse this broadcasting capability and send useless information to other stations in  
the network. To prevent this information from being seen across the link on the other LAN segment, a filter mask  
can be used.  
To prevent broadcast information from being passed across the link, use the following filter mask:  
0-FFFFFFFFFFFF  
This prevents any frame with a destination address field set to the broadcast address from being passed to the second  
LAN segment across the link.  
Ethernet Multicasting  
An Ethernet multicast is a frame of data where the destination address has the high-order bit set to a “one” condition.  
It is similar to a broadcast, but is to be received by a “group” of stations that meet the remainder of the address. In  
this manner, a broadcast is focused to a specific group of stations.  
To filter multicast frames, the following mask could be used: 0-’1XXX’X  
In this example the high-order bit by multi-cast definition must be set to a “one”. The single quotes around the first  
four positions instructs that the four positions constitute 4 bits, or a nibble, of the entire expression; each position  
representing a single bit. The “1” indicates that that bit position must be equal to a “1” before the expression is true.  
The X’s that are included within the single quotes represent a single don’t care for those bit positions in the first  
nibble. The X that is located outside of the single quotes represents a don’t care condition for the later nibble.  
NOTE: With this mask, both broadcast frames and multicast frames will be filtered.  
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Programmable Filtering  
General Restrictions  
Bridge Filter Masks may be created to generally restrict access for various purposes. Some of these purposes may be to filter  
specific combinations of information. This section will generally depict masks that may be created to control traffic across the  
bridged LAN network.  
Internet Addresses  
Within the Internet Protocol, there exist two address fields that are designated the Source and Destination Internet  
Addresses. It is these addresses that the IP uses for routing purposes.  
To filter Internet Addresses, a mask must be created to look at the Source or Destination address field within the IP  
header.  
As an example, assume a station’s Internet address is equal to 128.001.002.003, and a restriction is desired to prevent  
any other station from across the link on the opposite LAN from gaining access to it. In this case, the mask must  
filter any IP packet that is destined for this Internet address. The Destination address field within the IP header is at  
an offset of 30 octets into the Ethernet frame. This address is four octets long.  
(Note: Although an Internet address is written in decimal notation, the address within the IP header is always in  
hexadecimal.)  
To accomplish this, the mask would look like this: 12-0800&30-80010203  
This will filter IP packets that contain the Internet address of 128.001.002.003.  
As another example, assume that this Internet address should also be filtered if it originates any data. In addition to  
the mask above, an OR condition will have to be added to look at the IP source address. The new mask would be as  
follows: 12-0800&(26-80010203|30-80010203)  
This would filter any frame that is both an IP packet destined for or originating from Internet address  
128.001.002.003. The parenthesis must be added around the Internet portion to ensure that the proper logical  
ordering is retained.  
Ethernet Station Addresses  
Ethernet addresses are assigned to LAN users in blocks. These blocks are normally assigned to manufacturers of  
Ethernet LAN hardware, and the blocks are sufficiently large to provide unique addresses for a given manufacturer  
for many years.  
Thus, a manufacturer will have a block of addresses, and filtering may be performed to prevent a particular  
manufacturer’s LAN hardware from using the bridge facilities.  
As an example, Xerox has a block of addresses that cover the range from 0000AA000000 to 0000AAFFFFFF. To  
prevent this equipment from accessing facilities on another LAN segment, a generic filter may be created. A mask  
that looked at the Source Ethernet address field would be required. The mask would be as follows : 6-0000AA  
The remainder of the address is considered a “don’t care” condition. This mask results in the entire address block  
from using the segment LAN facilities.  
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Programmable Filtering  
Mask Combinations  
Mask combinations may be required to ensure that a frame is sufficiently qualified before the decision to filter is  
made. The qualification a frame must go through before a filter decision is made depends on the reason for the filter.  
Nonetheless, a few examples below have been provided that should aid in the creation of a mask that may require  
that extra little bit of qualification.  
Example  
To prevent a specific Ethernet station from accessing any TCP/IP host on the other segment. Assume the Ethernet  
address is 01-02-03-04-05-06.  
The mask would be: 6-010203040506&12-0800&23-06  
Example  
To prevent a specific protocol type from accessing a specific Ethernet Address. Assume the Ethernet address is 01-  
02-03-04-05-06, and the protocol type is Appletalk®. The filter mask would be: 0-010203040506&12-809B  
Example  
To prevent any Ethernet address with the 10th bit set to a 0 from accessing a LAT host or an IP host with an Internet  
address of 128.001.001.128.  
This particular mask, although not particularly useful, might be best served by creating two masks instead of one long  
mask. The decision is up to the Bridge Manager, but a longer mask is always more difficult to understand later. Both  
methods are presented below:  
Combined Filters 4-X’XX0X’&(12-6004|(12-0800&30-80010180))  
Separate Filters 4-X’XX0X’&12-6004  
4-X’XX0X’&12-0800&30-80010180  
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Programmable Filtering  
IP Router Pattern Filtering  
Pattern filtering may be used on any portion of the IP frame. IP pattern filtering behaves the same as bridge pattern filtering,  
except the start of the IP frame is offset 0, because the IP router function of the bridge/router handles only the IP frame  
itself.  
IP pattern filtering may use any combination of filtering operators as described in the bridge pattern filters.  
Protocol Discrimination  
Protocol discrimination may be required to prevent or limit the protocols within an IP frame that may traverse a routed Local  
Area Network.  
In Local Area Networks, there may be many different Transport layer protocols that coexist within the IP Network layer.  
TCP, UDP, and ICMP are just a few of the common protocols in use today. Each of these protocols is encapsulated within  
an IP frame, and therefore is subject to the IP routing function. If you would like to discriminate against a particular protocol  
to prevent its usage of the routed LAN facilities the P1705 & P1730 Router provides programmable filter masks that may be  
defined to act on any part of the IP frame.  
The IP Router Filter Patterns menu is located under the Filter Set-Up Menu. Within the IP Router Filter Patterns Menu there  
exists a Help function that can be used as a reference during IP Router Filter Pattern creation. This Help function includes all  
of the logical operators that may be applied to the mask expression.  
IPX Router Pattern Filtering  
Pattern filtering may be used on any portion of the IPX frame. IPX pattern filtering behaves the same as bridge pattern  
filtering, except the start of the IPX frame is offset 0, because the IPX router function of the bridge/router handles only the  
IPX frame itself.  
IPX pattern filtering may use any combination of filtering operators as described in the bridge pattern filters.  
The IPX Router Filter Patterns menu is located under the Filter Set-Up Menu. Within the IPX Router Filter Patterns Menu,  
there exists a Help function that can be used as a reference during IPX Router Filter Pattern creation. This Help function  
includes all of the logical operators that may be applied to the mask expression.  
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Appendix C - Frame Formats  
This appendix provides octet locations for the various portions of three of the common Ethernet frames. When creating  
pattern filters these diagrams will assist in the correct definition of the patterns. The offset numbers are indicated by the  
numbers above the frame representations.  
Note the differences in the TCP/IP and Novell frames when bridging and when routing. When routing, the TCP/IP and  
Novell frames are examined after the Level 2 Ethernet portion of the frame has been stripped from the whole data frame.  
This means that the offset numbers now start from 0 at the beginning of the routed frame and not the bridged frame.  
Some of the common Ethernet type codes are also shown here. The Ethernet type codes are located at offset 12 of the  
bridged Ethernet frame.  
Octet Locations on a Bridged TCP/IP Frame  
Octet Locations on a Bridged Novell Netware Frame  
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Frame Formats  
ETHERNET TYPE CODES  
Type Code  
0800  
Description  
DOD IP  
0801  
X.75 Internet  
0804  
Chaosnet  
0805  
X.25 Level 3  
0806  
ARP  
0807  
XNS Compatibility  
DEC MOP Dump/Load  
DEC MOP Remote Console  
DEC DECNET Phase IV Route  
DEC LAT  
6001  
6002  
6003  
6004  
6005  
DEC Diagnostic Protocol  
DEC Customer Protocol  
DEC LAVC, SCA  
Reverse ARP  
6006  
6007  
8035  
803D  
803F  
809B  
80D5  
80F3  
8137-8138  
814C  
8863  
DEC Ethernet Encryption  
DEC LAN Traffic Monitor  
Appletalk  
IBM SNA Service on Ether  
AppleTalk AARP (Kinetics)  
Novell, Inc.  
SNMP  
PPPoE Discovery Stage  
8864  
PPPoE Data Stage  
Octet Locations on an IP Routed TCP/IP Frame  
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Frame Formats  
Octet Locations on an IPX Routed Novell Netware Frame  
Octet Locations on a Bridged XNS Frame  
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