Configuring ISO CLNS

The following example shows an OSI network NSAP address format:

|     Domain|Area|     System ID| S|
47.0004.004D.0003.0000.0C00.62E6.00
 

The following example shows an GOSIP NSAP address structure. This structure is mandatory for addresses allocated from the International Code Designator (ICD) 0005 addressing domain. Refer to the GOSIP document, U.S. Government Open Systems Interconnection Profile (GOSIP), draft version 2.0, April 1989, for more information.

|                    Domain|Area|     System ID| S|
47.0005.80.ffff00.0000.ffff.0004.0000.0c00.62e6.00
 |   |    |    |    |    |
AFI IDI  DFI  AAI  Resv  RD

If an incoming packet has a destination NSAP address that does not match any existing NSAP addresses in the routing table, the Cisco IOS software will try to match the NSAP address with an NSAP prefix to route the packet. In the routing table, the best match means the longest NSAP prefix entry that matches the beginning of the destination NSAP address.

Table 5: Hierarchical Routing Examples

Datagram Destination NSAP Address	Table Entry Number Used
47.0005.000c.0001.0000.3456.01	1
47.0005.000c.0001.6789.2345.01	1
47.0004.1234.1234.1234.1234.01	2
47.0005.0003.4321.4321.4321.01	3
47.0005.000c.0004.5678.5678.01	4
47.0005.0001.0005.3456.3456.01	5

Octet boundaries must be used for the internal boundaries of NSAP addresses and NETs.

When you configure only ISO CLNS and not routing protocols, the Cisco IOS software only makes forwarding decisions. It does not perform other routing-related functions. In such a configuration, the software compiles a table of adjacency data, but does not advertise this information. The only information that is inserted into the routing table is the NSAP and NET addresses of this router, static routes, and adjacency information.

• ISO IGRP

• IS-IS

ESs communicate with ISs using the ES-IS protocol. Level 1 and Level 2 ISs communicate with each other using either ISO IS-IS or the Cisco ISO IGRP protocol.

• If your network includes WAN links that involve paying for connect time or for per-packet charges, you would use static routing, rather than pay to run a routing protocol and all its routing update packets over that link.

• If you want routers to advertise connectivity to external networks, but you are not running an interdomain routing protocol, you must use static routes.

• If you must interoperate with equipment from another vendor that does not support any of the dynamic routing protocols that Cisco supports, you must use static routing.

• For operation over X.25, Frame Relay, or SMDS networks, static routing is generally preferable.

Note An interface that is configured for static routing cannot reroute around failed links.

To configure ISO IGRP dynamic routing on the router, use the following commands in global configuration mode:

	Command	Purpose
Step 1	router iso-igrp [tag]	Enable the ISO IGRP routing process and enter router configuration mode.
Step2	net network-entity-title	Configure the NET or address for the routing process.

To configure ISO IGRP dynamic routing on the interface, use the following command in interface configuration mode:

Command	Purpose
clns router iso-igrp tag [level2]	Enable ISO IGRP on specified interfaces; also set the level type for routing updates.

NoteAdjusting the ISO IGRP metric can dramatically affect network performance, so ensure that all metric adjustments are made carefully. Because of the complexity of this task, it is not recommended unless it is done with guidance from an experienced system designer.

You can use different metrics for the ISO IGRP routing protocol on CLNS. To configure the metric constants used in the ISO IGRP composite metric calculation of reliability and load, use the following command in router configuration mode:

Command	Purpose
metric weights qos k1 k2 k3 k4 k5	Adjust the ISO IGRP metric.

Two additional ISO IGRP metrics can be configured: the bandwidth and delay associated with an interface. Refer to the Cisco IOS Interface Command Reference publication for details about the bandwidth (interface) and delay interface configuration commands used to set these metrics.

NoteUsing the bandwidth (interface) and delay commands to change the values of the ISO IGRP metrics also changes the values of IP IGRP metrics.

To adjust ISO IGRP timing parameters, use the following command in router configuration mode:

Command	Purpose
timers basic update-interval holddown-interval invalid-interval	Adjust the ISO IGRP timers (in seconds).

Split horizon blocks information about routes from being advertised out the interface from which that information originated. This feature usually optimizes communication among multiple routers, particularly when links are broken.

To either enable or disable split horizon for ISO IGRP updates, use the following commands in interface configuration mode:

Command	Purpose
clns split-horizon	Enable split horizon for ISO IGRP updates.
no clns split-horizon	Disable split horizon for ISO IGRP updates.

The default for all LAN interfaces is for split horizon to be enabled; the default for WAN interfaces on X.25, Frame Relay, or Switched Multimegabit Data Service (SMDS) networks is for split horizon to be disabled.

	Command	Purpose
Step1	Router#router isis [area tag]	Enables IS-IS routing for the specified routing process, and places you in router configuration mode. Use the area tag argument to identify the area to which this IS-IS router instance is assigned. A value for tag is required if you are configuring multiple IS-IS areas. The first IS-IS instance configured is Level1-2 by default. Later instances are automatically Level1. You can change the level of routing to be performed by a particular routing process using the is-type command.
Step2	Router(config)#net network-entity-title	Configures NETs for the routing process. Specify an NET for each routing process if you are configuring multiarea IS-IS. You can specify a name for a NET and for an address.

• Splitting up an area---Nodes within a given area can accumulate to a point that they are difficult to manage, cause excessive traffic, or threaten to exceed the usable address space for an area. Multiple area addresses can be assigned so that you can smoothly partition a network into separate areas without disrupting service.

• Merging areas---Use transitional area addresses to merge as many as three separate areas into a single area that shares a common area address.

• Change to a different address---You may need to change an area address for a particular group of nodes. Use multiple area addresses to allow incoming traffic intended for an old area address to continue being routed to associated nodes.

You must statically assign multiple area addresses on a router. Cisco currently supports assignment of up to three area addresses on a router. All the addresses must have the same system ID. For example, you can assign one address (area1 plus system ID), and two additional addresses in different areas (area2 plus system ID and area3 plus system ID) where the system ID is the same. The number of areas allowed in a domain is unlimited.

A router can dynamically learn about any adjacent router. As part of this process, the routers inform each other of their area addresses. If two routers share at least one area address, the set of area addresses of the two routers are merged. A merged set cannot contain more than three addresses. If there are more than three, the three addresses with the lowest numerical values are kept, and all others are dropped.

To configure multiple area addresses in IS-IS areas, use the following commands beginning in global configuration mode:

	Command	Purpose
Step1	Router#router isis [area tag]	Enables IS-IS routing for the specified routing process, and places you in router configuration mode. Use the area tag argument to identify the area to which this IS-IS router instance is assigned. A value for tag is required if you are configuring multiple IS-IS areas. The first IS-IS instance configured is Level1-2 by default. Later instances are automatically Level1. You can change the level of routing to be performed by a particular routing process using the is-type command.
Step2	Router(config)#net network-entity-title	Configures NETs for the routing process. Specify a NET for each routing process if you are configuring multiarea IS-IS. You can specify a name for a NET and for an address.

See the "NETs Configuration Examples" section at the end of this chapter for examples of configuring NETs and multiple area addresses.

To configure the link-state metric, use the following command in interface configuration mode:

Command	Purpose
isis metric default-metric {level-1 | level-2}	Configure the metric (or cost) for the specified interface.

The hold time determines how long a neighbor waits for another hello packet before declaring the neighbor down. This time determines how quickly a failed link or neighbor is detected so that routes can be recalculated.

To set the advertised hello interval and multiplier, use the following commands in interface configuration mode:

	Command	Purpose
Step1	isis hello-interval seconds {level-1 | level-2}	Specify the length of time between hello packets that the Cisco IOS software sends.
Step2	isis hello-multiplier multiplier [level-1 | level-2]	Specify the number of IS-IS hello packets a neighbor must miss before the router should declare the adjacency as down.

The hello interval can be configured independently for Level 1 and Level 2, except on serial point-to-point interfaces. (Because there is only a single type of hello packet sent on serial links, the hello packet is independent of Level 1 or Level 2.) Specify an optional level for X.25, SMDS, and Frame Relay multiaccess networks.

Use the isis hello-multiplier command in circumstances where hello packets are lost frequently and IS-IS adjacencies are failing unnecessarily. You can raise the hello multiplier and lower the hello interval (isis hello-interval command) correspondingly to make the hello protocol more reliable without increasing the time required to detect a link failure.

Command	Purpose
isis csnp-interval seconds {level-1 | level-2}	Configure the IS-IS CSNP interval for the specified interface.

The isis csnp-interval command does not apply to serial point-to-point interfaces. It does apply to WAN connections if the WAN is viewed as a multiaccess meshed network.

To set the retransmission level, use the following command in interface configuration mode:

Command	Purpose
isis retransmit-interval seconds	Configure the number of seconds between retransmission of IS-IS LSPs for point-to-point links.

The value you specify should be an integer greater than the expected round-trip delay between any two routers on the network. The setting of this parameter should be conservative, or needless retransmission will result. The value you determine should be larger for serial lines and virtual links.

If you specify Level 2 only, a Level 2 adjacency is established. If the neighbor router is a Level 1 router, no adjacency is established.

To configure area or domain passwords, use the following commands in router configuration mode:

Command	Purpose
area-password password	Configure the area authentication password.
domain-password password	Configure the routing domain authentication password.

You can completely block flooding (full blocking) on specific interfaces, so that new LSPs will not be flooded out over those interfaces. However, if flooding is blocked on a large number of links, and all remaining links go down, routers cannot synchronize their link-state databases even though there is connectivity to the rest of the network. When the link-state database is no longer updated, routing loops usually result.

To use CSNPs on selected point-to-point links to synchronize the link-state database, configure a CSNP interval using the isis csnp-interval command on selected point-to-point links over which normal flooding is blocked. You should use CSNPs for this purpose only as a last resort.

Configuring mesh groups (a set of interfaces on a router) can help to limit redundant flooding. All routers reachable over the interfaces in a particular mesh group are assumed to be densely connected (each router has many links to other routers), where many links can fail without isolating one or more routers from the network.

Normally, when a new LSP is received on an interface, it is flooded out over all other interfaces on the router. When the new LSP is received over an interface that is part of a mesh group, the new LSP will not be flooded out over the other interfaces that are part of that same mesh group.

Mesh groups rely on a full mesh of links between a group of routers. If one or more links in the full mesh goes down, the full mesh is broken, and some routers might miss new LSPs, even though there is connectivity to the rest of the network. When you configure mesh groups to optimize or limit LSP flooding, be sure to select alternative paths over which to flood in case interfaces in the mesh group go down.

To minimize the possibility of incomplete flooding, you should allow unrestricted flooding over at least a minimal set of links in the mesh. Selecting the smallest set of logical links that covers all physical paths results in very low flooding, but less robustness. Ideally you should select only enough links to ensure that LSP flooding is not detrimental to scaling performance, but enough links to ensure that under most failure scenarios no router will be logically disconnected from the rest of the network.

To configure the IS-IS level, use the following command in router configuration mode:

Command	Purpose
is-type {level-1 | level-1-2 | level-2-only}	Configure the IS-IS level at which the router is to operate.

The IS-IS protocol definition requires that a received LSP with an incorrect data-link checksum be purged by the receiver, which causes the initiator of the LSP to regenerate it. However, if a network has a link that causes data corruption while still delivering LSPs with correct data-link checksums, a continuous cycle of purging and regenerating large numbers of LSPs can occur, rendering the network nonfunctional.

To allow the router to ignore LSPs with an internal checksum error, use the following command in router configuration mode:

Command	Purpose
ignore-lsp-errors	Ignore LSPs with internal checksum errors rather than purging the LSPs.

To configure CLNS on the router, use the following commands in global configuration mode:

	Command	Purpose
Step1	clns routing	Configure CLNS.
Step2	clns net {net-address | name}	Assign an NSAP address to the router if the router has not been configured to route CLNS packets dynamically using ISO IGRP or IS-IS.
Step3	clns route nsap-prefix {next-hop-net | name}	Enter a specific static route.

NoteIf you have not configured the router to route CLNS packets dynamically using ISO IGRP or IS-IS, you must assign an address to the router.

To configure CLNS on an interface, use the following commands in interface configuration mode:

	Command	Purpose
Step1	clns enable	Enable ISO CLNS for each interface.
Step2	clns net {nsap-address | name}	Optionally, assign an NSAP address to a specific interface.

It is sometimes desirable for a router to have a neighbor configured statically rather than learned through ES-IS, ISO IGRP, or IS-IS.

NoteIt is necessary to use static mapping only for ESs that do not support ES-IS. The Cisco IOS software continues to dynamically discover ESs that do support ES-IS.

NoteIf you have configured interfaces for ISO IGRP or IS-IS, the ES-IS routing software automatically turns on ES-IS for those interfaces.

Command	Purpose
clns es-neighbor nsap snpa	Configure all end systems that will be used when you manually specify the NSAP-to-SNPA mapping.
clns is-neighbor nsap snpa	Configure all intermediate systems that will be used when you manually specify the NSAP-to-SNPA mapping.

To define a name-to-NSAP address mapping, use the following command in global configuration mode:

Command	Purpose
clns host name nsap	Define a name-to-NSAP address mapping.

The assigned NSAP name is displayed, where applicable, in show and debug EXEC commands. However, some effects and requirements are associated with using names to represent NETs and NSAP addresses.

The clns host global configuration command is generated after all other CLNS commands when the configuration file is parsed. As a result, you cannot edit the NVRAM version of the configuration to specifically change the address defined in the original clns host command. You must specifically change any commands that refer to the original address. These changes affect all commands that accept names.

The commands that are affected by these requirements include the following:

• net (router configuration command)

• clns is-neighbor (interface configuration command)

• clns es-neighbor (interface configuration command)

• clns route (global configuration command)

To enable or disable DNS queries for ISO CLNS addresses, use the following commands in global configuration mode:

Command	Purpose
ip domain-lookup nsap	Enable DNS queries for CLNS addresses.
no ip domain-lookup nsap	Disable DNS queries for CLNS addresses.

Command	Purpose
clns template-alias name template	Create aliases for frequently used address templates.
clns filter-set sname [permit | deny] template	Build filter sets of multiple address template permit and deny conditions.
clns filter-expr ename term	Build filter expressions, using one or more filter sets.

To apply filter expressions to an interface, use the following commands in interface configuration mode:

Command	Purpose
clns access-group name [in | out]	Apply a filter expression to frames forwarded in or out of an interface.
isis adjacency-filter name [match-all]	Apply a filter expression to IS-IS adjacencies.
iso-igrp adjacency-filter name	Apply a filter expression to ISO IGRP adjacencies.
clns adjacency-filter {es | is} name	Apply a filter expression to ES or IS adjacencies.

For IS-IS routing, redistribution of all area addresses of all Level1 areas into Level2 is implicit, and no additional configuration is required for this redistribution. Explicit redistribution between IS-IS areas cannot be configured. Redistribution from any other routing protocol into a particular area is possible, and is configured per router instance using the redistribute and route map commands. By default, redistribution is into Level2.

NoteIt is not necessary to use redistribution between areas. Redistribution only occurs for Level2 routing.

To configure the router to redistribute routing information into the ISO IGRP domain, use the following commands in global configuration mode:

Command	Purpose
router iso-igrp [tag]	Specify the routing protocol and tag (if applicable) into which you want to distribute routing information.
redistribute iso-igrp [tag] [route-map map-tag]	Specify one or more ISO IGRP routing protocol and tag (if applicable) you want to redistribute.
redistribute isis [tag] [route-map map-tag]	Specify the IS-IS routing protocol and tag (if applicable) you want to redistribute.
redistribute static [clns | ip]	Specify the static routes you want to redistribute.

To configure the router to redistribute routing information into the IS-IS domains, use the following commands in global configuration mode:

Command	Purpose
router isis [tag]	Specify the routing protocol and tag (if applicable) into which you want to distribute routing information.
redistribute isis [tag] [route-map map-tag]	Specify the IS-IS routing protocol and tag (if applicable) you want to redistribute.

NoteBy default, static routes are redistributed into IS-IS.

To conditionally control the redistribution of routes between domains, use the following command in global configuration mode:

Command	Purpose
route-map map-tag {permit | deny} sequence-number	Define any route maps needed to control redistribution.

One or more match command and one or more set commands typically follow a route-map command to define the conditions for redistributing routes from one routing protocol into another. If there are no match commands, everything matches. If there are no set commands, nothing is done (other than the match).

The match route-map configuration command has multiple formats. The match commands may be given in any order, and all defined match criteria must be satisfied to cause the route to be redistributed according to the set actions given with the set commands.

To define the match criteria for redistribution of routes from one routing protocol into another, use at least one of the following commands in route-map configuration mode:

Command	Purpose
match clns address name [name...name]	Match routes that have a network address matching one or more of the specified names (the names can be a standard access list, filter set, or expression).
match clns next-hop name [name...name]	Match routes that have a next hop address matching one or more of the specified names (the names can be a standard access list, filter set, or expression).
match clns route-source name [name...name]	Match routes that have been advertised by routers matching one or more of the specified names (the names can be a standard access list, filter set, or expression).
match interface type number [typenumber...type number]	Match routes that have the next hop out matching one or more of the specified interfaces.
match metric metric-value	Match routes that have the specified metric.
match route-type {level-1 | level-2}	Match routes that have the specified route type.

To define set actions for redistribution of routes from one routing protocol into another, use at least one of the following commands in route-map configuration mode:

Command	Purpose
set level {level-1 | level-2 | level-1-2}	Set the routing level of the routes to be advertised into a specified are of the routing domain.
set metric metric-value	Set the metric value to give the redistributed routes.
set metric-type {internal | external}	Set the metric type to give the redistributed routes.
set tag tag-value	Set the tag value to associate with the redistributed routes.

When configuring an ES-IS router, be aware of the following:

• ES-IS does not run over X.25 links unless the broadcast facility is enabled.

• ES hello packets and IS hello packets are sent without options. Options in received packets are ignored.

The recipient of a hello packet creates an adjacency entry for the system that sent it. If the next hello packet is not received within the interval specified, the adjacency times out and the adjacent node is considered unreachable.

A default rate has been set for hello packets and packet validity; however, to change the defaults, use the following commands in global configuration mode:

Command	Purpose
clns configuration-time seconds	Specify the rate at which ES hello and IS hello packets are sent.
clns holding-time seconds	Allow the sender of an ES hello or IS hello packet to specify the length of time you consider the information in these packets to be valid.

A default rate has been set for the ES Configuration Timer (ESCT) option; however, to change the default, use the following command in interface configuration mode:

Command	Purpose
clns esct-time seconds	Specify how often the end system should send ES hello packet PDUs.

To use HDLC encapsulation, you must have a router at both ends of the link. If you use X.25 encapsulation, and if IS-IS or ISO IGRP is not used on an interface, you must manually enter the NSAP-to-X.121 address mapping. The LAPB, SMDS, Frame Relay, and X.25 encapsulations interoperate with other vendors.

Both ISO IGRP and IS-IS can be configured over WANs.

Configuring a serial line to use CLNS over X.25 requires configuring the general X.25 information and the CLNS-specific information. First, configure the general X.25 information. Then, enter the CLNS static mapping information.

You can specify X.25 nondefault packet and window sizes, reverse charge information, and so on. The X.25 facilities information that can be specified is exactly the same as in the x25 map interface configuration command described in the "Configuring X.25 and LAPB" chapter in the CiscoIOS Wide-Area Networking Configuration Guide.

Changing the MTU value with the mtu interface configuration command can affect the CLNS MTU value. If the CLNS MTU is at its maximum given the interface MTU, the CLNS MTU will change with the interface MTU. However, the reverse is not true; changing the CLNS MTU value has no effect on the value for the mtu interface configuration command.

To set the CLNS MTU packet size for a specified interface, use the following command in interface configuration mode:

Command	Purpose
clns mtu bytes	Set the MTU size of the packets sent on the interface.

NoteThe CTR card does not support the switching of frames larger than 4472 bytes. Interoperability problems might occur if CTR cards are intermixed with other Token Ring cards on the same network. These problems can be minimized by lowering the CLNS MTU sizes to be the same on all routers on the network.

You can set an interval time between ERPDUs. Setting a minimum interval between ERDPUs can reduce the amount of bandwidth used by ERDPUs. When you set a minimum interval between ERPDUs, the Cisco IOS software does not send ERPDUs more frequently than one per millisecond on the specified interface, where milliseconds is the argument used in the clnserpdu-interval command for setting the minimal interval time between ERPDUs.

To send ERPDUs and set the minimum interval time between ERPDUs, use the following commands in interface configuration mode:

	Command	Purpose
Step1	clns send-erpdu	Send an ERPDU when the routing software detects an error in a data PDU; this is enabled by default.
Step2	clns erpdu-interval milliseconds	Set the minimum interval time, in milliseconds, between ERPDUs.

Command	Purpose
clear clns cache	Clear and reinitialize the CLNS routing cache.
clear clns es-neighbors	Remove ES neighbor information from the adjacency database.
clear clns is-neighbors	Remove IS neighbor information from the adjacency database.
clear clns neighbors	Remove CLNS neighbor information from the adjacency database.
clear clns route	Remove dynamically derived CLNS routing information.
ping clns {host | address}	Invoke a diagnostic tool for testing connectivity.
show clns	Display information about the CLNS network.
show clns cache	Display the entries in the CLNS routing cache.
show clns area-tag es-neighbors [type number] [detail]	Display ES neighbor entries, including the associated areas.
show clns filter-expr [name] [detail]	Display filter expressions.
show clns filter-set [name]	Display filter sets.
show clns interface [type number]	List the CLNS-specific or ES-IS information about each interface.
show clns area-tag is-neighbors [type number] [detail]	Display IS neighbor entries, according to the area in which they are located.
show clns area-tag neighbors [type number] [detail]	Display both ES and IS neighbors.
show clns area-tag neighbor areas	Display information about IS-IS neighbors and the areas to which they belong.
show clns area-tag protocol [domain | area-tag]	List the protocol-specific information for each IS-IS or ISO IGRP routing process in this router.
show clns route [nsap]	Display all the destinations to which this router knows how to route CLNS packets.
show clns area-tag traffic	Display information about the CLNS packets this router has seen.
show isis area-tag database [level-1] [level-2] [l1] [l2] [detail] [lspid]	Display the IS-IS link-state database.
show isis area-tag routes	Display the IS-IS Level 1 routing table.
show isis area-tag spf-log	Display a history of the shortest path first (SPF) calculations for IS-IS.
show isis area-tag topology	Display a list of all connected routers in all areas.
show route-map [map-name]	Display all route maps configured or only the one specified.
trace clns destination	Discover the paths taken to a specified destination by packets in the network.
which-route {nsap-address | clns-name}	Display the routing table in which the specified CLNS destination is found.

Requests for information and associated responses are sent as TARP PDUs, which are sent as Connectionless Network Protocol (CLNP) data packets. TARP PDUs are distinguished by a unique N-selector in the NSAP address. Following are the five types of TARP PDUs:

TARP can be used for a conventional IS-IS configuration with a single Level1 and a Level2 area (or configuration with a single Level1 area or a Level2 area).

If multiple Level1 areas are defined, the router resolves addresses using TARP in the following way:

1. The router obtains the NSAP of the Level2 area, if present, from the locally assigned target identifier.

2. If only Level 1 areas are configured, the router uses the NSAP of the first active Level 1 area as shown in the configuration at the time of TARP configuration ("tarp run"). (Level 1 areas are sorted alphanumerically by tag name, with capital letters coming before lowercase letters. For example, AREA-1 precedes AREA-2, which precedes area-1.) Note that the TID NSAP could change following a reload if a new Level 1 area is added to the configuration after TARP is running.

3. The router continues to process all Type 1 and 2 PDUs that are for this router. Type 1 PDUs are processed locally if the target identifier is in the local TID cache. If not, they are "propagated" (routed) to all interfaces in the same Level1 area. (The same area is defined as the area configured on the input interface.)

4. Type 2 PDUs are processed locally if the specified target identifier is in the local TID cache. If not, they are propagated via all interfaces (all Level1 or Level2 areas) with TARP enabled. If the source of the PDU is from a different area, the information is also added to the local TID cache. Type 2 PDUs are propagated via all static adjacencies.

5. Type 4 PDUs (for changes originated locally) are propagated to all Level1 and Level2 areas (because internally they are treated as "Level1-2").

6. Type 3 and 5 PDUs continue to be routed.

7. Type 1 PDUs are only "propagated" (routed) via Level1 static adjacencies if the static NSAP is in one of the Level1 areas in this router.

The router will use the CLNS capability to send and receive TARP PDUs. If the router is configured as an IS, the router must be running IS-IS. If the router is configured as an ES, the router must be running ES-IS.

To turn on the TARP functionality, use the following commands in global configuration mode:

Command	Purpose
tarp run	Turn on the TARP functionality.
tarp tid tid	Assign a TID to the router.

To enable TARP on one or more interfaces, use the following command in interface configuration mode:

Command	Purpose
tarp enable	Enable TARP on the interface.

To disable TID-to-NSAP address mapping in the TID cache, use the following command in global configuration mode:

Command	Purpose
no tarp allow-caching	Disable TARP TID-to-NSAP address mapping.

To disable origination and propagation of TARP PDUs, use the following commands in global configuration mode:

Command	Purpose
no tarp originate	Disable TARP PDU origination.
no tarp global-propagate	Disable global propagation of TARP PDUs.

To disable propagation of TARP PDUs on a specific interface, use the following command in interface configuration mode:

Command	Purpose
no tarp propagate [all | message-type type-number [type-number] [type-number]]	Disable propagation of TARP PDUs on the interface.

To create a TID-to-NSAP static route, use the following command in global configuration mode:

Command	Purpose
tarp map tid nsap	Enter a TID-to-NSAP static route.

To create a static TARP adjacency, use the following command in global configuration mode:

Command	Purpose
tarp route-static nsap [all | message-type type-number [type-number] [type-number]]	Enter a static TARP adjacency.

To stop TARP from propagating PDUs to an IS-IS/ES-IS adjacency that may not have TARP running, TARP provides a blacklist adjacency capability. The router will not propagate TARP PDUs to blacklisted routers.

To blacklist a router, use the following command in global configuration mode:

Command	Purpose
tarp blacklist-adjacency nsap	Bypass a router not running TARP.

Command	Purpose
tarp query nsap	Get the TID associated with a specific NSAP.
tarp resolve tid [1 | 2]	Get the NSAP associated with a specific TID.

To determine the TID, the router first checks the local TID cache. If there is a TID entry in the local TID cache, the requested information is displayed. If there is no TID entry in the local TID cache, a TARP Type 5 PDU is sent out to the specified NSAP address.

To determine the NSAP address, the router first checks the local TID cache. If there is an NSAP entry in the local TID cache, the requested information is displayed. If there is no NSAP entry in the local TID cache, a TARP Type 1 or Type 2 PDU is sent out. By default, a Type 1 PDU is sent to all Level1 (IS-IS and ES-IS) neighbors. If a response is received, the requested information is displayed. If a response is not received within the response time, a Type 2 PDU is sent to all Level 1 and Level 2 neighbors. Specifying the tarp resolve tid 2 EXEC command causes only a Type 2 PDU to be sent.

You can configure the length of time that the router will wait for a response (in the form of a Type 3 PDU).

You can configure the amount of time that the router waits to receive a response from a Type 1 PDU, a Type 2 PDU, and a Type 5 PDU. You can also configure lifetime of the PDU based on the number of hops.

You can also set timers that control how long dynamically created TARP entries remain in the TID cache, and how long the system ID-to-sequence number mapping entry remains in the loop detection buffer table. The loop detection buffer table prevents TARP PDUs from looping.

To configure TARP PDU timers, control PDU lifetime, and set how long entries remain in cache, use the following commands in global configuration mode:

Command	Purpose
tarp t1-response-timer seconds	Configure the number of seconds that the router will wait for a response from a TARP Type 1 PDU.
tarp t2-response-timer seconds	Configure the number of seconds that the router will wait for a response from a TARP Type 2 PDU.
tarp post-t2-response-tim er seconds	Configure the number of seconds that the router will wait for a response from a TARP Type 2 PDU after the default timer has expired.
tarp arp-request-timer seconds	Configure the number of seconds that the router will wait for a response from a TARP Type 5 PDU.
tarp lifetime hops	Configure the number of routers that a TARP PDU can traverse before it is discarded.
tarp cache-timer seconds	Configure the number of seconds a dynamically created TARP entry remains in the TID cache.
tarp ldb-timer seconds	Configure the number of seconds that a system ID-to-sequence number mapping entry remains in the loop detection buffer table.

To configure miscellaneous PDU information, use the following commands in global configuration mode:

Command	Purpose
tarp sequence-number number	Change the sequence number in the next outgoing TARP PDU.
tarp urc [0 | 1]	Set the update remote cache bit in all subsequent outgoing TARP PDUs so that the remote router does or does not update the cache.
tarp nselector-type hex-digit	Specify the N-selector used to identify TARP PDUs.
tarp protocol-type hex-digit	Specify the protocol type used in outgoing TARP PDUs. Only Fast Ethernet (FE) (to indicate Connectionless Network Protocol (CLNP)) is supported.

Command	Purpose
clear tarp counters	Reset the TARP counters that are shown with the show tarp traffic command.
clear tarp ldb-table	Remove all system ID-to-sequence number mapping entries in the TARP loop detection buffer table.
clear tarp tid-table	Remove all dynamically created TARP TID-to-NSAP address mapping entries in the TID cache.
show tarp	Display all global TARP parameters.
show tarp blacklisted-adjacencies	List all adjacencies that are blacklisted (that is, adjacencies that will not receive propagated TARP PDUs).
show tarp host tid	Display information about a specific TARP router stored in the local TID cache.
show tarp interface [type number]	List all interfaces on the router that have TARP enabled.
show tarp ldb	Display the contents of the loop detection buffer table.
show tarp map	List all the static entries in the TID cache.
show tarp static-adjacencies	List all static TARP adjacencies.
show tarp tid-cache	Display information about the entries in the TID cache.
show tarp traffic	Display statistics about TARP PDUs.

! define a tag castor for the routing process 
router iso-igrp castor 
! configure the net for the process in area 2, domain 47.0004.004d
net 47.0004.004d.0002.0000.0C00.0506.00
! specify iso-igrp routing using the previously specified tag castor
interface ethernet 0
clns router iso-igrp castor
! specify iso-igrp routing using the previously specified tag castor
interface ethernet 1
clns router iso-igrp castor
! specify iso-igrp routing using the previously specified tag castor
interface serial 0
clns router iso-igrp castor

! define a tag orion for the routing process 
router iso-igrp orion 
! configure the net for the process in area 1, domain 47.0004.004d
net 47.0004.004d.0001.212223242526.00
! specify iso-igrp routing using the previously specified tag orion 
interface ethernet 0
clns router iso-igrp orion
! specify iso-igrp routing using the previously specified tag orion 
interface ethernet 1
clns router iso-igrp orion

Router Chicago

The following example shows how to configure Router Chicago for dynamic interdomain routing:

! define a tag A for the routing process 
router iso-igrp A
! configure the NET for the process in area 2, domain 47.0007.0200
net 47.0007.0200.0002.0102.0104.0506.00
! redistribute iso-igrp routing information throughout domain A
redistribute iso-igrp B
! define a tag B for the routing process 
router iso-igrp B
! configure the NET for the process in area 3, domain 47.0006.0200
net 47.0006.0200.0003.0102.0104.0506.00
! redistribute iso-igrp routing information throughout domain B
redistribute iso-igrp A
! specify iso-igrp routing with the tag A
interface ethernet 0
clns router iso-igrp A
! specify iso-igrp routing with the tag B
interface serial 0
clns router iso-igrp B

Router Detroit

The following example shows how to configure Router Detroit for dynamic interdomain routing. Comment lines have been eliminated from this example to avoid redundancy.

router iso-igrp B 
net 47.0006.0200.0004.0102.0104.0506.00
redistribute iso-igrp C
router iso-igrp C 
net 47.0008.0200.0005.0102.01040.506.00
redistribute iso-igrp B
interface serial 0
clns router iso-igrp B
interface serial 1
clns router iso-igrp C
 

Chicago injects a prefix route for domain A into domain B. Domain B injects this prefix route and a prefix route for domain B into domain C.

OSI Configuration

The following example shows an OSI configuration example. In this example, IS-IS runs with two area addresses, metrics tailored, and different circuit types specified for each interface. Most comment lines have been eliminated from this example to avoid redundancy.

! enable is-is routing in area 1
router isis area1
! Router is in areas 47.0004.004d.0001 and 47.0004.004d.0011
net 47.0004.004d.0001.0000.0c11.1111.00
net 47.0004.004d.0011.0000.0c11.1111.00
! enable the router to operate as a station router and an interarea router
is-type level-1-2
!
interface ethernet 0
clns router isis area1
! specify a cost of 5 for the level-1 routes
isis metric 5 level-1
! establish a level-1 adjacency
isis circuit-type level-1
!
interface ethernet 1
clns router isis area1
isis metric 2 level-2
isis circuit-type level-2-only
!
interface serial 0
clns router isis area1
isis circuit-type level-1-2
! set the priority for serial 0 to 3 for a level-1 adjacency
isis priority 3 level-1
isis priority 1 level-2

The following example shows route redistribution between IS-IS and ISO IGRP domains. In this case, the IS-IS domain is on Ethernet interface 0; the ISO IGRP domain is on serial interface 0. The IS-IS routing process is assigned a null tag; the ISO IGRP routing process is assigned a tag of remote-domain. Most comment lines have been eliminated from this example to avoid redundancy.

router isis
net 39.0001.0001.0000.0c00.1111.00
! redistribute iso-igrp routing information throughout remote-domain
redistribute iso-igrp remote-domain
!
router iso-igrp remote-domain
net 39.0002.0001.0000.0c00.1111.00
! redistribute is-is routing information 
redistribute isis
!
interface ethernet 0
clns router isis
!
interface serial 0
clns router iso-igrp remote

router iso-igrp test-proc1
! 001F in the following net is the hex value for area 31
net 49.0001.001F.aaaa.aaaa.aaaa.00
router iso-igrp test-proc2
! 0028 in the following net is the hex value for area 40 
net 49.0001.0028.aaaa.aaaa.aaaa.00 
!
interface ethernet 1
clns router iso-igrp test-proc1
!
interface serial 2
clns router iso-igrp test-proc1
!
interface ethernet 2
clns router iso-igrp test-proc2

IS-IS

clns host sid 39.0001.1111.1111.1111.00
clns host bar 39.0002.2222.2222.2222.00
! assign a static address for the router
clns net sid
! enable CLNS packets to be routed
clns routing
! pass ISO CLNS packet traffic to end systems without routing them
interface ethernet 0
clns enable
! pass ISO CLNS packet traffic to end systems without routing them
interface ethernet 1
clns enable
! specify end system for static routing 
clns es-neighbor bar 0000.0C00.62e7
! create an interface-static route to bar for packets with the following NSAP address
clns route 47.0004.000c bar

The following example shows one way to configure the Router Chicago:

! define the name chicago to be used in place of the following NSAP
clns host chicago 47.0004.0050.0001.0000.0c00.243b.00
! define the name detroit to be used in place of the following NSAP
clns host detroit 47.0004.0050.0002.0000.0c00.1e12.00
! enable ISO IGRP routing of CLNS packets
router iso-igrp sales
! configure net chicago, as defined above
net chicago
! specify iso-igrp routing using the previously specified tag sales
interface ethernet 0
clns router iso-igrp sales
! set the interface up as a DTE with X.25 encapsulation 
interface serial 0
encapsulation x25
x25 address 1111
x25 nvc 4
! specify iso-igrp routing using the previously specified tag sales 
clns router iso-igrp sales
! define a static mapping between Detroit's nsap and its X.121 address
x25 map clns 2222 broadcast
 

This configuration brings up an X.25 virtual circuit between the Router Chicago and the Router Detroit. Routing updates will be sent across this link. This implies that the virtual circuit could be up continuously.

If the Chicago office should grow to contain multiple routers, it would be appropriate for each of those routers to know how to get to Router Detroit. Add the following command to redistribute information between routers in Chicago:

router iso-igrp sales 
redistribute static

The following example shows how to configure Router A for static interdomain routing:

! define tag orion for net 47.0006.0200.0100.0102.0304.0506.00
router iso-igrp orion 
! configure the following network entity title for the routing process
net 47.0006.0200.0100.0102.0304.0506.00
! define the tag bar to be used in place of Router B's NSAP
clns host bar 47.0007.0200.0200.1112.1314.1516.00
! specify iso-igrp routing using the previously specified tag orion 
interface ethernet 0
clns router iso-igrp orion
! pass ISO CLNS traffic to end systems without routing 
interface serial 1
clns enable
! configure a static route to Router B
clns route 47.0007 bar
 

The following example shows how to configure Router B for static interdomain routing:

router iso-igrp pleiades 
! configure the network entity title for the routing process
net 47.0007.0200.0200.1112.1314.1516.00
! define the name sid to be used in place of Router A's NSAP
clns host sid 47.0006.0200.0100.0001.0102.0304.0506.00
! specify iso-igrp routing using the previously specified tag pleiades 
interface ethernet 0
clns router iso-igrp pleiades
! pass ISO CLNS traffic to end systems without routing 
interface serial 0
clns enable
! pass packets bound for sid in domain 47.0006.0200 through serial 0
clns route 47.0006.0200 sid
 

CLNS routing updates will not be sent on the serial link; however, CLNS packets will be sent and received over the serial link.

Router A

router iso-igrp test-proc
net 49.0001.aaaa.aaaa.aaaa.00
!
interface serial 1
clns router iso-igrp test-proc
! assume the host is a DTE and encapsulates x.25
encapsulation x25
! define the X.121 address of 31101 for serial 1
X25 address 31101
! set up an entry for the other side of the X.25 link (Router B)
x25 map clns 31101 broadcast

Router B

router iso-igrp test-proc
net 49.0001.bbbb.bbbb.bbbb.00
!
interface serial 2
clns router iso-igrp test-proc
! configure this side as a DCE
encapsulation x25-dce
! define the X.121 address of 31102 for serial 2
X25 address 31102
! configure the NSAP of Router A and accept reverse charges
x25 map clns 31101 broadcast accept-reverse

Basic TARP Configuration Example

The following example shows how to enable TARP on the router and interface Ethernet 0. The router is assigned the TID myname.

clns routing
tarp run
tarp tid myname
 
interface ethernet 0
tarp enable

Complex TARP Configuration Example

clns routing
tarp run 
tarp cache-timer 300
tarp route-static 49.0004.1234.1234.1234.00 
tarp blacklist-adjacency 49.0001.7777.7777.7777.00 
tarp tid myname
interface ethernet 0
tarp enable