Cisco IOS IP Routing: ISIS Command Reference

log-adjacency-changes

To configure the router to send a syslog message when an Open Shortest Path First (OSPF) neighbor goes up or down, use the log-adjacency-changes command in router configuration mode. To turn off this function, use the no form of this command.

log-adjacency-changes [detail]

no log-adjacency-changes [detail]

Syntax Description

Command Default

Enabled

Command Modes

Router configuration

Command History

Usage Guidelines

This command allows you to know about OSPF neighbors going up or down without turning on the debug ip ospf packet command or the debug ipv6 ospf adjacency command. The log-adjacency-changes command provides a higher level view of those changes of the peer relationship with less output than the debug command provides. The log-adjacency-changes command is on by default but only up/down (full/down) events are reported, unless the detail keyword is also used.

Examples

The following example configures the router to send a syslog message when an OSPF neighbor state changes:

log-adjacency-changes detail

Related Commands

lsp-full suppress

To control which routes are suppressed when the link-state protocol data unit (PDU) becomes full, use the lsp-full suppress command in router configuration mode. To stop suppression of redistributed routes, specify the none keyword or use the no form of this command.

lsp-full suppress {external [interlevel] | interlevel [external] | none}

no lsp-full suppress

Syntax Description

Command Default

Redistributed routes are suppressed.

Command Modes

Router configuration (config-router)

Command History

Usage Guidelines

In networks where there is no limit placed on the number of redistributed routes into IS-IS (that is, the redistribute maximum-prefix command was not configured), it is possible that the link-state PDU (LSP) could become full and routes will be dropped. Use the lsp-full suppress command to define in advance which routes are suppressed in the event that the LSP becomes full.

The external and interlevel keywords can be specified together or separately.

Use the clear isis lsp-full command to clear the LSPFULL state.

Examples

The following example shows how to specify that if the LSP becomes full, both redistributed routes and routes from another level will be suppressed from the LSP:

router isis

 lsp-full suppress interlevel external

Related Commands

lsp-gen-interval (IPX)

To set the minimum interval at which link-state packets (LSPs) are generated, use the lsp-gen-interval command in router configuration mode. To restore the default interval, use the no form of this command.

lsp-gen-interval seconds

no lsp-gen-interval seconds

Syntax Description

Defaults

5 seconds

Command Modes

Router configuration

Command History

Usage Guidelines

The lsp-gen-interval command controls the rate at which LSPs are generated on a per-LSP basis. For instance, if a link is changing state at a high rate, the default value of the LSP generation interval limits the signaling of this change to once every 5 seconds. Because the generation of an LSP may cause all routers in the area to perform the SPF calculation, controlling this interval may have area-wide impact. Raising this interval can reduce the load on the network imposed by a rapidly changing link.

Examples

The following example sets the minimum interval at which LSPs are generated to 10 seconds:

lsp-gen-interval 10

Related Commands

lsp-gen-interval (IS-IS)

To customize IS-IS throttling of LSP generation, use the lsp-gen-interval command in router configuration mode. To restore default values, use the no form of this command.

lsp-gen-interval [level-1 | level-2] lsp-max-wait [lsp-initial-wait lsp-second-wait]

no lsp-gen-interval

Syntax Description

Defaults

lsp-max-wait: 5 seconds
lsp-initial-wait: 50 milliseconds
lsp-second-wait: 5000 milliseconds

Command Modes

Router configuration

Command History

Usage Guidelines

The following description will help you determine whether to change the default values of this command:

•The lsp-initial-wait argument indicates the initial wait time (in milliseconds) before generating the first LSP.

•The third argument indicates the amount of time to wait (in milliseconds) between the first and second LSP generation.

•Each subsequent wait interval is twice as long as the previous one until the wait interval reaches the lsp-max-wait interval specified, so this value causes the throttling or slowing down of the LSP generation after the initial and second intervals. Once this interval is reached, the wait interval continues at this interval until the network calms down.

•After the network calms down and there are no triggers for 2 times the lsp-max-wait interval, fast behavior is restored (the initial wait time).

Notice that the lsp-gen-interval command controls the delay between LSPs being generated, as opposed to the following related commands:

•The isis lsp-interval command sets the delay (in milliseconds) between successive LSPs being transmitted (including LSPs generated by another system and forwarded by the local system).

•The isis retransmit-interval command sets the amount of time (in seconds) between retransmissions of the same LSP on a point-to-point link.

•The isis retransmit-throttle-interval command sets the minimum delay (in milliseconds) between retransmitted LSPs on a point-to-point interface.

These commands can be used in combination to control the rate of LSP packets being generated, transmitted, and retransmitted.

Examples

The following example configures intervals for SPF calculations, PRC, and LSP generation:

router isis

 spf-interval 5 10 20

 prc-interval 5 10 20

 lsp-gen-interval 2 50 100

Related Commands

lsp-refresh-interval (IS-IS)

To set the link-state packet (LSP) refresh interval, use the lsp-refresh-interval command in router configuration mode. To restore the default refresh interval, use the no form of this command.

lsp-refresh-interval seconds

no lsp-refresh-interval

Syntax Description

Defaults

900 seconds (15 minutes)

Command Modes

Router configuration

Command History

Usage Guidelines

The refresh interval determines the rate at which Cisco IOS software periodically transmits in LSPs the route topology information that it originates. This is done to keep the database information from becoming too old.

LSPs must be periodically refreshed before their lifetimes expire. The value set for the lsp-refresh-interval command should be less than the value set for the max-lsp-lifetime command; otherwise, LSPs will time out before they are refreshed. If you misconfigure the LSP lifetime to be too low compared to the LSP refresh interval, the software will reduce the LSP refresh interval to prevent the LSPs from timing out.

Reducing the refresh interval reduces the amount of time that undetected link state database corruption can persist at the cost of increased link utilization. (This is an extremely unlikely event, however, because there are other safeguards against corruption.) Increasing the interval reduces the link utilization caused by the flooding of refreshed packets (although this utilization is very small).

Examples

The following example configures the IS-IS LSP refresh interval to be 1080 seconds (18 minutes):

router isis 

 lsp-refresh-interval 1080

Related Commands

max-area-addresses

To configure additional manual addresses for an IS-IS area, use the max-area-addresses command in router configuration mode. To disable the manual addresses, use the no form of this command.

max-area-addresses number

no max-area-addresses number

Syntax Description

Command Default

No manual addresses are configured for an IS-IS area.

Command Modes

Router configuration

Command History

Usage Guidelines

The max-area-addresses command allows you to maximize the size of an IS-IS area by configuring additional manual addresses. You specify the number of manual addresses that you want to add by entering the max-area-addresses command, and you assign a NET address to create each manual address by entering the net command.

Examples

The following example configures three manual addresses as follows:

router isis

 max-area-addresses 3

 net 50.3131.3131.3131.00

 net 51.3131.3131.3131.00

 net 52.3131.3131.3131.00

In the following example, an error message appears because the user has exceeded the maximum number of manual addresses that were configured with the max-area-addresses command:

router isis

 max-area-addresses 2

 net 50.3131.3131.3131.00 

 net 51.3131.3131.3131.00 

 net 52.3131.3131.3131.00 

%The maximum allowed addresses already configured

Related Commands

metric

To globally change the metric value for all Intermediate System-to-Intermediate System (IS-IS) interfaces, use the metric command in interface configuration mode or address family configuration mode. To disable the metric value and reinstate the default metric value of 10, use the no form of this command.

metric default-value [level-1 | level-2]

no metric default-value [level-1 | level-2]

Syntax Description

Defaults

The default value for active IS-IS interfaces is 10; the default value for inactive IS-IS interfaces is 0. If the level-1 or level-2 keyword is not entered, the metric will be applied to both Level 1 and Level 2 IS-IS interfaces.

Command Modes

Interface configuration
Address family configuration

Command History

Usage Guidelines

When you need to change the default metric value for all IS-IS interfaces, it is recommended to use the metric command in order to configure all interfaces globally. Globally configuring the metric values prevents user errors, such as unintentionally removing a set metric from an interface without configuring a new value and unintentionally allowing the interface to revert to the default metric of 10, thereby becoming a highly preferred interface in the network.

For networks running IPv4, enter the metric command in interface configuration mode. For networks running IPv6, enter the metric command in address family configuration mode.

Once you enter the metric command to change the default IS-IS interface metric value, an enabled interface will use the new value instead of the default value of 10. Passive interfaces will continue to use the metric value of 0.

Note The metric value that is directly configured for a specific interface with either the isis metric command or the isis ipv6 metric command will always take precedence over the metric value that you configure with the metric command.

Examples

The following example configures the IS-IS interfaces with a global default value of 111 for an IS-IS IPv4 network:

interface Ethernet3/1

 ip address 10.10.10.2 255.255.0.0

 ip router isis area1

 no ip route-cache

 duplex half

!

interface Ethernet3/2

 ip address 10.10.10.130 255.255.255.0

 ip router isis area1

 no ip route-cache

 duplex half

!

router isis area1

 net 01.0000.0309.1234.00

 metric-style wide

 metric 111

Entering the show clns interface command returns the following information:

Router# show clns interface

Ethernet3/1 is up, line protocol is up

  Checksums enabled, MTU 1497, Encapsulation SAP

  ERPDUs enabled, min. interval 10 msec.

  CLNS fast switching enabled

  CLNS SSE switching disabled

  DEC compatibility mode OFF for this interface

  Next ESH/ISH in 39 seconds

  Routing Protocol: IS-IS

    Circuit Type: level-1-2

    Interface number 0x0, local circuit ID 0x1

    Level-1 Metric: 111, Priority: 64, Circuit ID: mekong.01

    Level-1 IPv6 Metric: 10

    Number of active level-1 adjacencies: 0

    Level-2 Metric: 111, Priority: 64, Circuit ID: mekong.01

    Level-2 IPv6 Metric: 10

    Number of active level-2 adjacencies: 0

    Next IS-IS LAN Level-1 Hello in 922 milliseconds

    Next IS-IS LAN Level-2 Hello in 1 seconds

Ethernet3/2 is up, line protocol is up

  Checksums enabled, MTU 1497, Encapsulation SAP

  ERPDUs enabled, min. interval 10 msec.

  CLNS fast switching enabled

  CLNS SSE switching disabled

  DEC compatibility mode OFF for this interface

  Next ESH/ISH in 20 seconds

  Routing Protocol: IS-IS

    Circuit Type: level-1-2

    Interface number 0x1, local circuit ID 0x2

    Level-1 Metric: 111, Priority: 64, Circuit ID: mekong.02

    Level-1 IPv6 Metric: 10

    Number of active level-1 adjacencies: 1

    Level-2 Metric: 111, Priority: 64, Circuit ID: mekong.02

    Level-2 IPv6 Metric: 10

    Number of active level-2 adjacencies: 1

    Next IS-IS LAN Level-1 Hello in 2 seconds

    Next IS-IS LAN Level-2 Hello in 1 seconds

The following example configures IPv6 for IS-IS and a global default value of 222 IPv6 metric for the IS-IS interfaces. The metric of 10 that was entered using the isis metric command will take precedence.

interface Ethernet3/1

 ip address 10.10.10.2 255.255.0.0

 ip router isis area1

 no ip route-cache

 duplex half

 isis metric 10

!

interface Ethernet3/2

 ip address 10.10.10.10 255.255.255.0

 ip router isis area1

 no ip route-cache

 duplex half

router isis area1

 net 01.0000.0309.1234.00

 metric-style wide

 metric 111

 !

 address-family ipv6

 metric 222

 exit-address-family

Enter the show clns interface command to verify that the global default metric for IS-IS IPv6 interfaces for IPv6 network is 222:

Router# show clns interface

Ethernet3/1 is up, line protocol is up

  Checksums enabled, MTU 1497, Encapsulation SAP

  ERPDUs enabled, min. interval 10 msec.

  CLNS fast switching enabled

  CLNS SSE switching disabled

  DEC compatibility mode OFF for this interface

  Next ESH/ISH in 51 seconds

  Routing Protocol: IS-IS

    Circuit Type: level-1-2

    Interface number 0x0, local circuit ID 0x1

    Level-1 Metric: 10, Priority: 64, Circuit ID: mekong.01

    Level-1 IPv6 Metric: 222

    Number of active level-1 adjacencies: 0

    Level-2 Metric: 10, Priority: 64, Circuit ID: mekong.01

    Level-2 IPv6 Metric: 222

    Number of active level-2 adjacencies: 0

    Next IS-IS LAN Level-1 Hello in 2 seconds

    Next IS-IS LAN Level-2 Hello in 2 seconds

Ethernet3/2 is up, line protocol is up

  Checksums enabled, MTU 1497, Encapsulation SAP

  ERPDUs enabled, min. interval 10 msec.

  CLNS fast switching enabled

  CLNS SSE switching disabled

  DEC compatibility mode OFF for this interface

  Next ESH/ISH in 17 seconds

  Routing Protocol: IS-IS

    Circuit Type: level-1-2

    Interface number 0x1, local circuit ID 0x2

    Level-1 Metric: 111, Priority: 64, Circuit ID: mekong.02

    Level-1 IPv6 Metric: 222

    Number of active level-1 adjacencies: 1

    Level-2 Metric: 111, Priority: 64, Circuit ID: mekong.02

    Level-2 IPv6 Metric: 222

    Number of active level-2 adjacencies: 1

    Next IS-IS LAN Level-1 Hello in 1 seconds

    Next IS-IS LAN Level-2 Hello in 89 milliseconds

Related Commands

metric-style wide

To configure a router running Intermediate System-to-Intermediate System (IS-IS) so that it generates and accepts only new-style type, length, value objects (TLVs), use the metric-style wide command in router configuration mode. To disable this function, use the no form of this command.

metric-style wide [transition] [level-1 | level-2 | level-1-2]

no metric-style wide [transition] [level-1 | level-2 | level-1-2]

Syntax Description

Command Default

The Multiprotocol Label Switching (MPLS) traffic engineering image generates only old-style TLVs. To do MPLS traffic engineering, new-style TLVs that have wider metric fields must be generated.

Command Modes

Router configuration (config-router)

Command History

Usage Guidelines

If you enter the metric-style wide command, a router generates and accepts only new-style TLVs. Therefore, the router uses less memory and other resources than it would if it generated both old-style and new-style TLVs.

This style is appropriate for enabling MPLS traffic engineering across an entire network.

Note This discussion of metric styles and transition strategies is oriented toward traffic engineering deployment. Other commands and models could be appropriate if the new-style TLVs are desired for other reasons. For example, a network might require wider metrics, but might not use traffic engineering.

Examples

The following example shows how to configure a router to generate and accept only new-style TLVs on level 1:

Router(config-router)# metric-style wide level-1

Related Commands

net

To configure an Intermediate System-to-Intermediate System (IS-IS) network entity title (NET) for the routing process, use the net command in global configuration mode. To remove a NET, use the no form of this command.

net net1 alt net2

no net net

Syntax Description

Defaults

The defaults are as follows:

•No NET is configured.

•The IS-IS process is disabled.

Command Modes

Global configuration

Command History

Usage Guidelines

An IS (Intermediate system) is identified by an address known as a network access point (NASAP). The NSAP is divided up into three parts as specified by ISO/AI 10589:

Area address—This field is of variable length, composed of high order octets, and it excludes the System ID and N-selector (NSEL) fields. This area address is associated wit a single area within the routing domain.

System ID—This field is 6 octets long and should be set to a unique value with Level 1 and Level 2. The system IS defines an end system (ES) or an IS in an area. You configure the area address and the system ID with the NET command. You can display the system ID with the show isis topology command.

NSEL—This field is called the N-selector, also referred to as the NSAP, and it specifies the upper-layer protocol. The NSEL is the last byte of the NSAP and identifies a network service user. A network service user is a transport entity or the IS network entity itself. When the N-selector is set to zero, the entire NSAP is called a network entity title (NET).

A NET is an NSAP where the last byte is always the n-selector and is always zero. A NET can be from 8 to 20 bytes in length.

Under most circumstances, you should configure one NET only. It is possible to configure two or three NETs, but you should not configure more than one NET except for the following unusual circumstances:

•A network configuration has multiple areas that are merged.

•One area in the IS-IS process is being split into multiple areas.

Configuring multiple NETs in these two circumstances can be temporarily useful because multiple area addresses enable you to renumber an area individually as needed.

When entering the value for the net argument, use these guidelines:

•In a 3-slot chassis, slot 1 is the primary slot and slot 2 is the alternate slot.

•In a 6-slot chassis, slot 5 is the primary slot and slot 6 is the alternate slot.

•In a 9-slot chassis, slot 5 is the primary slot and slot 6 is the alternate slot.

•In a 13-slot chassis, slot 7 is the primary slot and slot 8 is the alternate slot.

If you are using IS-IS to perform IP routing only (no connectionless network service routing is enabled), you must configure a NET to define the router ID and area ID.

Examples

The following example shows how to configure a router with a NET which consists of the system ID 0000.0c11.1110 and area address 47.0004.004d.0001:

router isis firstcompany

 net 47.0004.004d.0001.0001.0c11.1111.00

The following example shows three IS-IS routing processes with three areas that are configured. Each area has a unique identifier, but the system ID is the same for all areas.

clns routing

.

.

.

interface Tunnel529

 ip address 10.0.0.5 255.255.255.0

 ip router isis BB

 clns router isis BB

interface Ethernet1

 ip address 10.1.1.5 255.255.255.0

 ip router isis A3253-01

 clns router isis A3253-01

!

interface Ethernet2

 ip address 10.2.2.5 255.255.255.0

 ip router isis A3253-02

 clns router isis A3253-02

.

.

.

router isis BB                          ! Defaults to "is-type level-1-2"

 net 49.2222.0000.0000.0005.00

!

router isis A3253-01

 net 49.0553.0001.0000.0000.0005.00

 is-type level-1

!

router isis A3253-02

 net 49.0553.0002.0000.0000.0005.00

 is-type level-1

Related Commands

partition avoidance

To cause an Intermediate System-to-Intermediate System (IS-IS) Level 1-2 border router to stop advertising the Level 1 area prefix into the Level 2 backbone when full connectivity is lost between the border router, all adjacent Level 1 routers, and end hosts, use the partition avoidance command in router configuration mode. To disable this output format, use the no form of the command.

partition avoidance area-tag

no partition avoidance area-tag

Syntax Description

Defaults

This command is disabled by default.

Command Modes

Router configuration

Command History

Usage Guidelines

When the partition avoidance command is enabled, a multiarea router withdraws a Level 1 area prefix from the Level 2 backbone when it no longer has any active adjacencies to that Level 1 area. This withdrawal prevents the Level 1 area from appearing to be partitioned within the Level 2 backbone.

In International Organization for Standardization (ISO) CLNS networks using a redundant topology, it is possible for an area to become "partitioned" when full connectivity is lost between a Level 1-2 border router, all adjacent Level 1 routers, and end hosts. In such a case, multiple Level 1-2 border routers advertise the Level 1 area prefix into the backbone area, even though any one router can reach only a subset of the end hosts in the Level 1 area.

When enabled, the partition avoidance command prevents this partitioning by causing the border router to stop advertising the Level 1 area prefix into the Level 2 backbone. This command displays the output from different areas as a string or additional white space.

Other cases of connectivity loss within the Level 1 area itself are not detected or corrected by the border router, and this command will have no effect.

Examples

The following example causes the routing process named Finance to stop advertising the prefix for the area named area1 when the router no longer has any active adjacencies to area1:

router isis Finance

 partition avoidance area1

Related Commands

prc-interval

To customize Intermediate System-to-Intermediate System (IS-IS) throttling of partial route calculations (PRC), use the prc-interval command in router configuration mode. To restore default values, use the no form of this command.

prc-interval prc-max-wait [prc-initial-wait prc-second-wait]

no prc-interval

Syntax Description

Defaults

prc-max-wait: 5 seconds
prc-initial-wait: 2000 milliseconds
prc-second-wait: 5000 milliseconds

Command Modes

Router configuration

Command History

Usage Guidelines

PRC is the software's process of calculating routes without performing an shortest path first (SPF) calculation. This is possible when the topology of the routing system itself has not changed, but a change is detected in the information announced by a particular IS or when it is necessary to attempt to reinstall such routes in the Routing Information Base (RIB).

The following description will help you determine whether to change the default values of this command:

•The prc-initial-wait argument indicates the initial wait time (in milliseconds) before generating the first link-state packet (LSP).

•The prc-second-wait argument indicates the amount of time to wait (in milliseconds) between the first and second LSP generation.

•Each subsequent wait interval is twice as long as the previous one until the wait interval reaches the prc-max-wait interval specified, so this value causes the throttling or slowing down of the PRC calculation after the initial and second intervals. Once this interval is reached, the wait interval continues at this interval until the network calms down.

•After the network calms down and there are no triggers for 2 times the prc-max-wait interval, fast behavior is restored (the initial wait time).

Examples

The following example configures intervals for SPF calculations, PRC, and LSP generation:

router isis

 spf-interval 5 10 20

 prc-interval 5 10 20

 lsp-gen-interval 2 50 100

protocol shutdown

To disable the Intermediate System-to-Intermediate System (IS-IS) protocol so that it cannot form any adjacency on any interface and will clear the IS-IS link-state packet (LSP) database, use the protocol shutdown command in router configuration mode. To reenable the IS-IS protocol, use the no form of this command.

protocol shutdown

no protocol shutdown

Syntax Description

This command has no arguments or keywords.

Defaults

No default behavior or values

Command Modes

Router configuration

Command History

Usage Guidelines

The protocol shutdown command allows you to disable the IS-IS protocol for a specific routing instance without removing any existing IS-IS configurations parameters. When you enter the protocol shutdown command, the IS-IS protocol will continue to run on the router, and you can use the current IS-IS configuration, but IS-IS will not form any adjacencies on any interface, and it will also clear the IS-IS LSP database.

If you want to disable the IS-IS protocol for a specific interface, use the isis protocol shutdown command.

Examples

The following example disables the IS-IS protocol for a specific routing instance:

Router(config)# router isis area1

Router(config-router)# protocol shutdown

Related Commands

redistribute isis

To redistribute Intermediate System-to-Intermediate System (IS-IS) routes specifically from Level 1 into Level 2 or from Level 2 into Level 1, use the redistribute isis command in router configuration mode. To disable the redistribution, use the no form of this command.

redistribute isis ip {level-1 | level-2} into {level-2 | level-1} [[distribute-list list-number] | [route-map map-tag]]

no redistribute isis ip {level-1 | level-2} into {level-2 | level-1}{[distribute-list list-number] | [route-map map-tag]}

Syntax Description

Defaults

There are no default values for this command.

Command Modes

Router configuration

Command History

Usage Guidelines

Specify either level-l into level-2 or level-2 into level-1. You may optionally specify either a distribute list or a route map, but not both. You must also specify the metric-style wide command in order for the redistribute isis command to work.

In IS-IS, all areas are stub areas, which means that no routing information is leaked from the backbone (Level 2) into areas (Level 1). Level 1-only routers use default routing to the closest Level 1-Level 2 router in their area. This command enables you to redistribute Level 2 IP routes into Level 1 areas. This redistribution enables Level 1-only routers to pick the best path for an IP prefix to get out of the area. This is an IP-only feature, CLNS routing is still stub routing.

For more control and scalability, a distribute list or a route map can control which Level 2 IP routes can be redistributed into Level 1. This command allows large IS-IS-IP networks to use areas for better scalability.

Examples

In the following example, access list 100 controls the redistribution of IS-IS from Level 1 into Level 2:

router isis

 net 49.0000.0000.0001.00

 metric-style wide

 redistribute isis ip level-1 into level-2 distribute-list 100

access-list 100 permit ip 10.10.10.0 0.0.0.255 any

In the following example, the route map named "match-tag" controls the redistribution of IS-IS from Level 1 into Level 2 so that only routes tagged with 110 are redistributed:

router isis

 net 49.0000.0000.0001.00

 metric-style wide

 redistribute isis ip level-1 into level-2 route-map match-tag

route-map match-tag permit 10

 match tag 110

Related Commands

router isis

To enable the Intermediate System-to-Intermediate System (IS-IS) routing protocol and to specify an IS-IS process, use the router isis command in global configuration mode. To disable IS-IS routing, use the no form of this command.

router isis [area-tag]

no router isis [area-tag]

Syntax Description

Command Default

This command is disabled by default.

Command Modes

Global configuration (config)

Command History

Usage Guidelines

This command is used to enable routing for an area. An appropriate network entity title (NET) must be configured to specify the area address of the area and system ID of the router. Routing must be enabled on one or more interfaces before adjacencies may be established and dynamic routing is possible.

If you have IS-IS running and at least one International Standards Organization Interior Gateway Routing Protocol (ISO-IGRP) process, the IS-IS process and the ISO-IGRP process cannot both be configured without an area tag. The null tag can be used by only one process. If you run ISO-IGRP and IS-IS, a null tag can be used for IS-IS, but not for ISO-IGRP at the same time. However, each area in an IS-IS multiarea configuration should have a nonnull area tag to facilitate identification of the area.

You can configure only one IS-IS routing process to perform Level 2 (interarea) routing. You can configure this process to perform Level 1 (intra-area) routing at the same time. You can configure up to 29 additional processes as Level 1-only processes. If Level 2 routing is configured on any process, all additional processes are automatically configured as Level 1.

An interface cannot be part of more than one area, except in the case where the associated routing process is performing both Level 1 and Level 2 routing. On media such as WAN media where subinterfaces are supported, different subinterfaces could be configured for different areas.

If Level 2 routing is not desired for a given area, use the is-type command to remove Level 2. Level 2 routing can then be enabled on some other router instance.

Explicit redistribution between IS-IS instances is prohibited (prevented by the parser). In other words, you cannot issue a redistribute isis area-tag command in the context of another IS-IS router instance (router isis area-tag). Redistribution from any other routing protocol into a particular area is possible, and is configured per router instance, as in Cisco IOS Release 12.0, using the redistribute and route map commands. By default, redistribution is into Level 2.

If multiple Level 1 areas are defined, the Target Address Resolution Protocol (TARP) behaves in the following way:

•The locally assigned target identifier gets the network service access point (NSAP) of the Level 2 area, if present.

•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 target identifier NSAP could change following a reload if a new Level 1 area is added to the configuration after TARP is running.

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

•Type 2 PDUs are processed locally if the specified target identifier is in the local target identifier cache. If not, they are propagated via all interfaces (all Level 1 or Level 2 areas) with TARP enabled. If the source of the PDU is from a different area, the information is also added to the local target identifier cache. Type 2 PDUs are propagated via all static adjacencies.

•Type 4 PDUs (for changes originated locally) are propagated to all Level 1 and Level 2 areas (because internally they are treated as "Level 1-2").

•Type 3 and 5 PDUs continue to be routed.

•Type 1 PDUs are propagated only via Level 1 static adjacencies if the static NSAP is in one of the Level 1 areas in this router.

After you enter the router isis command, you can enter the maximum number of paths. There can be from 1 to 32 paths.

Examples

The following example shows how to configure IS-IS for IP routing, with system ID 0000.0000.0002 and area ID 01.0001, and enable IS-IS to form adjacencies on Ethernet interface 0 and serial interface 0. The IP prefix assigned to Ethernet interface 0 will be advertised to other IS-IS routers.

router isis tag1

 net 01.0001.0000.0000.0002

 is-type level-1

!

interface ethernet 0

 ip address 10.1.1.1 255.255.255.0

 ip router isis

!

interface serial 0

 ip unnumbered ethernet0

 ip router isis

The following example shows how to start IS-IS routing with the optional area-tag argument, where "example" is the value for the area-tag argument:

router isis example

The following example shows how to specify IS-IS as an IP routing protocol for a process named Finance, and specify that the Finance process will be routed on Ethernet interface 0 and serial interface 0:

router isis Finance

 net 49.0001.aaaa.aaaa.aaaa.00

interface Ethernet 0

 ip router isis Finance

interface serial 0

 ip router isis Finance

The following example shows usage of the maximum-paths option:

router isis

maximum-paths?

20

Related Commands

set-attached-bit

To specify constraints for when a Level 1 - Level 2 (L1L2) router should set its attached-bit, use the set-attached-bit command in router configuration mode. To disable this function, use the no form of this command.

set-attached-bit route-map map-tag

no set-attached-bit route-map map-tag

Syntax Description

Defaults

This command is disabled by default.

Command Modes

Router configuration

Command History

Usage Guidelines

In the current IS-IS implementation, as specified in ISO 10589, L1L2 routers set their Level 1 (L1) link-state packet (LSP) attached-bit when they see other areas in their own domain, or see other domains. However, in some network topologies, adjacent L1L2 routers in different areas may lose connectivity to the Level 2 (L2) backbone. Level 1 (L1) routers may then send traffic destined outside of the area or domain to L1L2 routers that may not have such connectivity.

To allow more control over the attached-bit setting for L1L2 routers, enter the set-attached-bit command in router configuration mode. The route map can specify one or more CLNS routes. If at least one of the match address route-map clauses matches a route in the L2 CLNS routing table, and if all other requirements for setting the attached-bit are met, the L1L2 router will continue to set the attached-bit in its L1 LSP. If the requirements are not met or no match address route-map clauses match a route in the L2 CLNS routing table, the attached-bit will not be set.

Note Wildcarded matches are not supported. For each route-map statement, an exact route lookup of the specified route will be performed. The first matched route will have other match statements applied.

Examples

In the following example, the attached-bit will stay set when the router matches 49.00aa in the L2 CLNS routing table.

router isis

 clns filter-set L2_backbone_connectivity permit 49.00aa

 route-map check-for-L2_backbone_connectivity

 match clns address L2_backbone_connectivity

router isis

 set-attached-bit route-map check-for-L2_backbone_connectivity

end

show clns route 49.00aa

Known via "isis", distance 110, metric 30, Dynamic Entry

Routing Descriptor Blocks:

 via tr2, Serial0

   isis, route metric is 30, route version is 58

Related Commands

set-overload-bit

To configure the router to signal other routers not to use it as an intermediate hop in their shortest path first (SPF) calculations, use the set-overload-bit command in router configuration mode. To remove the designation, use the no form of this command.

set-overload-bit [on-startup {seconds | wait-for-bgp}] [suppress [[interlevel] [external]]]

no set-overload-bit

Syntax Description

Defaults

The overload bit is not set.

Command Modes

Router configuration

Command History

Usage Guidelines

This command forces the router to set the overload bit (also known as the hippity bit) in its nonpseudonode link-state packets (LSPs). Normally, the setting of the overload bit is allowed only when a router runs into problems. For example, when a router is experiencing a memory shortage, it might be that the link-state database is not complete, resulting in an incomplete or inaccurate routing table. By setting the overload bit in its LSPs, other routers can ignore the unreliable router in their SPF calculations until the router has recovered from its problems.

The result will be that no paths through this router are seen by other routers in the IS-IS area. However, IP and Connectionless Network Service (CLNS) prefixes directly connected to this router will still be reachable.

This command can be useful when you want to connect a router to an IS-IS network but do not want real traffic flowing through it under any circumstances. Examples situations are as follows:

•A test router in the lab, connected to a production network.

•A router configured as an LSP flooding server, for example, on a nonbroadcast multiaccess (NBMA) network, in combination with the mesh group feature.

•A router that is aggregating virtual circuits (VCs) used only for network management. In this case, the network management stations must be on a network directly connected to the router with the set-overload-bit command configured.

Unless you specify the on-startup keyword, this command sets the overload bit immediately.

In addition to setting the overload bit, you might want to suppress certain types of IP prefix advertisements from LSPs. For example, allowing IP prefix propagation between Level 1 and Level 2 effectively makes a node a transit node for IP traffic, which might be undesirable. The suppress keyword used with the interlevel or external keyword (or both) accomplishes that suppression while the overload bit is set.

Examples

The following example sets the overload bit upon startup and until BGP has converged, and suppresses redistribution between IS-IS levels and suppresses redistribution from external routing protocols while the overload bit is set:

interface Ethernet0

 ip address 10.1.1.1 255.255.255.0

 ip router isis

router isis

 net 49.0001.0000.0000.0001.00

 set-overload-bit on-startup wait-for-bgp suppress interlevel external

router bgp 100

show clns interface

To list the CLNS-specific information about each interface, use the show clns interface command in privileged EXEC mode.

show clns interface [type number]

Syntax Description

Command Modes

Privileged EXEC

Command History

Examples

The following is sample output from the show clns interface command that includes information for Token Ring and serial interfaces:

Router# show clns interface

TokenRing 0 is administratively down, line protocol is down

  CLNS protocol processing disabled

TokenRing 1 is up, line protocol is up

  Checksums enabled, MTU 4461, Encapsulation SNAP

  ERPDUs enabled, min. interval 10 msec.

  RDPDUs enabled, min. interval 100 msec., Addr Mask enabled

  Congestion Experienced bit set at 4 packets

  CLNS fast switching disabled

  DEC compatibility mode OFF for this interface

  Next ESH/ISH in 18 seconds

  Routing Protocol: ISO IGRP

      Routing Domain/Area: <39.0003> <0020>

Serial 2 is up, line protocol is up

  Checksums enabled, MTU 1497, Encapsulation HDLC

ERPDUs enabled, min. interval 10 msec.

     RDPDUs enabled, min. interval 100 msec., Addr Mask enabled

     Congestion Experienced bit set at 4 packets

     CLNS fast switching enabled

     DEC compatibility mode OFF for this interface

     CLNS cluster alias enabled on this interface

     Next ESH/ISH in 48 seconds

  Routing Protocol: IS-IS

       Circuit Type: level-1-2

       Level-1 Metric: 10, Priority: 64, Circuit ID: 0000.0C00.2D55.0A

       Number of active level-1 adjacencies: 0

       Level-2 Metric: 10, Priority: 64, Circuit ID: 0000.0000.0000.00

       Number of active level-2 adjacencies: 0

       Next IS-IS LAN Level-1 hello in 3 seconds

       Next IS-IS LAN Level-2 hello in 3 seconds

Cisco IOS Release 12.2(18)SXE, 12.0(31)S, and 12.4(4)T

The following is sample output from the show clns interface command that verifies that the BFD feature has been enabled on Ethernet interface 3/0. The relevant command output is shown in bold in the output.

Router# show clns interface ethernet 3/0

Ethernet3/0 is up, line protocol is up

  Checksums enabled, MTU 1497, Encapsulation SAP

  ERPDUs enabled, min. interval 10 msec.

  CLNS fast switching enabled

  CLNS SSE switching disabled

  DEC compatibility mode OFF for this interface

  Next ESH/ISH in 42 seconds

  Routing Protocol: IS-IS

    Circuit Type: level-1-2

    Interface number 0x1, local circuit ID 0x2

    Level-1 Metric: 10, Priority: 64, Circuit ID: RouterA.02

    DR ID: 0000.0000.0000.00

    Level-1 IPv6 Metric: 10

    Number of active level-1 adjacencies: 0

    Level-2 Metric: 10, Priority: 64, Circuit ID: RouterA.02

    DR ID: 0000.0000.0000.00

    Level-2 IPv6 Metric: 10

    Number of active level-2 adjacencies: 0

    Next IS-IS LAN Level-1 Hello in 3 seconds

    Next IS-IS LAN Level-2 Hello in 5 seconds

    BFD enabled

Table 8 describes the significant fields shown in the display.

show clns is-neighbors

To display Intermediate System-to-Intermediate System (IS-IS) related information for IS-IS router adjacencies, use the show clns is-neighbors command in EXEC mode. Neighbor entries are sorted according to the area in which they are located.

show clns area-tag is-neighbors [type number] [detail]

Syntax Description

Command Modes

EXEC

Command History

Examples

The following is sample output from the show clns is-neighbors command:

Router# show clns is-neighbors

System Id       Interface   State  Type  Priority  Circuit Id         Format

0000.0C00.0C35  Ethernet1   Up     L1    64        0000.0C00.62E6.03  Phase V

0800.2B16.24EA  Ethernet0   Up     L1L2  64/64     0800.2B16.24EA.01  Phase V

0000.0C00.3E51  Serial1     Up     L2    0         04                 Phase V

0000.0C00.62E6  Ethernet1   Up     L1    64        0000.0C00.62E6.03  Phase V

Table 9 describes significant fields shown in the display.

The following is sample output from the show clns is-neighbors detail command:

Router# show clns is-neighbors detail

System Id       Interface   State  Type  Priority  Circuit Id         Format

0000.0C00.0C35  Ethernet1   Up     L1    64        0000.0C00.62E6.03  Phase V

  Area Address(es): 47.0004.004D.0001 39.0001

  Uptime: 0:03:35 

0800.2B16.24EA  Ethernet0   Up     L1L2  64/64     0800.2B16.24EA.01  Phase V

  Area Address(es): 47.0004.004D.0001

  Uptime: 0:03:35 

0000.0C00.3E51  Serial1     Up     L2    0         04                 Phase V

  Area Address(es): 39.0004

  Uptime: 0:03:35 

000.0C00.62E6  Ethernet1    Up     L1    64        0000.0C00.62E6.03  Phase V

  Area Address(es): 47.0004.004D.0001

  Uptime: 0:03:35 

Notice that the information displayed in show clns is-neighbors detail output includes everything shown in show clns is-neighbors output, but it also includes the area addresses associated with the IS neighbors (intermediate-system adjacencies) and how long (uptime) the adjacency has existed.

Related Commands

show clns traffic

To list the CLNS packets that this router has seen, use the show clns traffic command in user EXEC or privileged EXEC mode.

show clns area-tag traffic

Syntax Description

Command Modes

User EXEC
Privileged EXEC

Command History

Examples

The following is sample output from the show clns traffic command:

Router# show clns traffic

CLNS & ESIS Output: 139885, Input: 90406

CLNS Local: 0, Forward: 0

CLNS Discards:

  	Hdr Syntax: 150, Checksum: 0, Lifetime: 0, Output cngstn: 0

  No Route: 0, Dst Unreachable 0, Encaps. Failed: 0

  NLP Unknown: 0, Not an IS: 0

CLNS Options: Packets 19, total 19, bad 0, GQOS 0, cngstn exprncd 0

CLNS Segments: Segmented: 0, Failed: 0

CLNS Broadcasts: sent: 0, rcvd: 0

Echos: Rcvd 0 requests, 69679 replies

  Sent 69701 requests, 0 replies

ESIS(sent/rcvd): ESHs: 0/34, ISHs: 483/1839, RDs: 0/0, QCF: 0/0

ISO IGRP: Querys (sent/rcvd): 0/0 Updates (sent/rcvd): 1279/1402

ISO IGRP: Router Hellos: (sent/rcvd): 1673/1848

ISO IGRP Syntax Errors: 0

IS-IS: Level-1 Hellos (sent/rcvd): 0/0

IS-IS: Level-2 Hellos (sent/rcvd): 0/0

IS-IS: PTP Hellos (sent/rcvd): 0/0

IS-IS: Level-1 LSPs (sent/rcvd): 0/0

IS-IS: Level-2 LSPs (sent/rcvd): 0/0

IS-IS: Level-1 CSNPs (sent/rcvd): 0/0

IS-IS: Level-2 CSNPs (sent/rcvd): 0/0

IS-IS: Level-1 PSNPs (sent/rcvd): 0/0

IS-IS: Level-2 PSNPs (sent/rcvd): 0/0

IS-IS: Level-1 DR Elections: 0

IS-IS: Level-2 DR Elections: 0

IS-IS: Level-1 SPF Calculations: 0

IS-IS: Level-2 SPF Calculations: 0

Table 10 describes significant fields shown in the display.

show isis database

To display the Intermediate System-to-Intermediate System (IS-IS) link-state database, use the show isis database command in user EXEC or privileged EXEC mode.

show isis [process-tag] database [level-1 | l1] [level-2 | l2][detail] [lspid]

Syntax Description

Command Modes

User EXEC (>)
Privileged EXEC (#)

Command History

Usage Guidelines

The order of the optional argument and keywords is not important when this command is entered. For example, the following are both valid command specifications and provide the same output: show isis database detail l2 and show isis database l2 detail.

Examples

The following is sample output from the show isis database command:

Router# show isis database

IS-IS Level-1 Link State Database

LSPID                 LSP Seq Num    LSP Checksum  LSP Holdtime  ATT/P/OL

0000.0C00.0C35.00-00  0x0000000C     0x5696        792           0/0/0

0000.0C00.40AF.00-00* 0x00000009     0x8452        1077          1/0/0

0000.0C00.62E6.00-00  0x0000000A     0x38E7        383           0/0/0

0000.0C00.62E6.03-00  0x00000006     0x82BC        384           0/0/0

0800.2B16.24EA.00-00  0x00001D9F     0x8864        1188          1/0/0

0800.2B16.24EA.01-00  0x00001E36     0x0935        1198          1/0/0

IS-IS Level-2 Link State Database

LSPID                 LSP Seq Num    LSP Checksum  LSP Holdtime  ATT/P/OL

0000.0C00.0C35.03-00  0x00000005     0x04C8        792           0/0/0

0000.0C00.3E51.00-00  0x00000007     0xAF96        758           0/0/0

0000.0C00.40AF.00-00* 0x0000000A     0x3AA9        1077          0/0/0

The following is sample output from the show isis database command using the process-tag argument to display information about a VPN routing and forwarding instance (VRF)-aware IS-IS instance tagFirst:

Router# show isis tagFirst database level-2

Tag tagFirst:

IS-IS Level-2 Link State Database:

LSPID                 LSP Seq Num    LSP Checksum  LSP Holdtime  ATT/P/OL

igp-01.00-00          0x0000000A     0x5E73        914           0/0/0

igp-01.03-00          0x00000001     0x8E41        894           0/0/0

igp-01.04-00          0x00000001     0x8747        894           0/0/0

igp-03.00-00        * 0x00000005     0x55AD        727           0/0/0

igp-03.02-00        * 0x00000001     0x3B97        727           0/0/0

igp-02.00-0           0x00000004     0xC1FB        993           0/0/0

igp-02.01-00          0x00000001     0x448D        814           0/0/0

igp-04.00-00          0x00000004     0x76D0        892           0/0/0

Table 11 describes the significant fields shown in the display.

.

The following is sample output from the show isis database detail command:

Router# show isis database detail

IS-IS Level-1 Link State Database

LSPID                 LSP Seq Num  LSP Checksum  LSP Holdtime  ATT/P/OL

0000.0C00.0C35.00-00  0x0000000C   0x5696        325           0/0/0

  Area Address: 47.0004.004D.0001

  Area Address: 39.0001

  Metric: 10   IS 0000.0C00.62E6.03

  Metric: 0    ES 0000.0C00.0C35

0000.0C00.40AF.00-00* 0x00000009   0x8452        608           1/0/0

  Area Address: 47.0004.004D.0001

  Topology: IPv4 (0x0) IPv6 (0x2)

  NLPID: 0xCC 0x8E

  IP Address: 172.16.21.49

  Metric: 10   IS 0800.2B16.24EA.01

  Metric: 10   IS 0000.0C00.62E6.03

  Metric: 0    ES 0000.0C00.40AF

  IPv6 Address: 2001:0DB8::/32

  Metric: 10   IPv6 (MT-IPv6) 2001:0DB8::/64

  Metric: 5    IS-Extended cisco.03

  Metric: 10   IS-Extended cisco1.03

  Metric: 10    IS (MT-IPv6) cisco.03

As the output shows, in addition to the information displayed with the show isis database command, the show isis database detail command displays the contents of each LSP.

Table 12 describes the significant fields shown in the display.

.

The following is additional sample output from the show isis database detail command. This LSP is a Level 2 LSP. The area address 39.0001 is the address of the area in which the router resides.

Router# show isis database 12 detail

IS-IS Level-2 Link State Database

LSPID                 LSP Seq Num  LSP Checksum  LSP Holdtime  ATT/P/OL

0000.0C00.1111.00-00* 0x00000006   0x4DB3        1194          0/0/0

  Area Address: 39.0001

  NLPID:       0x81 0xCC

  IP Address:  172.16.64.17

  Metric: 10   IS 0000.0C00.1111.09

  Metric: 10   IS 0000.0C00.1111.08

  Metric: 10   IP 172.16.65.0 255.255.255.0

show isis database verbose

To display additional information about the Intermediate System-to-Intermediate System (IS-IS) database, use the show isis database verbose command in user EXEC or privileged EXEC mode.

show isis database verbose

Syntax Description

This command has no arguments or keywords.

Command Modes

User EXEC
Privileged EXEC

Command History

Examples

The following is sample output from the show isis database verbose command:

Router# show isis database verbose

IS-IS Level-1 Link State Database

LSPID                 LSP Seq Num  LSP Checksum  LSP Holdtime      ATT/P/OL

dtp-5.00-00         * 0x000000E6   0xC9BB        1042              0/0/0

  Area Address:49.0001

  NLPID:       0xCC 

  Hostname:dtp-5

  Router ID:   10.5.5.5

  IP Address:  172.16.39.5

  Metric:10         IP 172.16.39.0/24

dtp-5.00-01         * 0x000000E7   0xAB36        1065              0/0/0

  Metric:10         IS-Extended dtp-5.01

    Affinity:0x00000000

    Interface IP Address:172.21.39.5

    Physical BW:10000000 bits/sec

    Reservable BW:1166000 bits/sec

    BW Unreserved[0]: 1166000 bits/sec, BW Unreserved[1]: 1166000 bits/sec

    BW Unreserved[2]: 1166000 bits/sec, BW Unreserved[3]: 1166000 bits/sec

    BW Unreserved[4]: 1166000 bits/sec, BW Unreserved[5]: 1166000 bits/sec

    BW Unreserved[6]: 1166000 bits/sec, BW Unreserved[7]: 1153000 bits/sec

  Metric:0          ES dtp-5

Table 13 describes the significant fields shown in the display.

The following example includes a route tag:

Router# show isis database verbose

IS-IS Level-1 Link State Database:

LSPID                 LSP Seq Num    LSP Checksum    LSP Holdtime    ATT/P/OL

dasher.00-00          0x000000F8     0xE57B          518             1/0/0

  Area Address: 49.0002

  NSPID:        0xCC

  Hostname: dasher

  IP Address: 10.3.0.1

  Metric: 10     IP 172.16.170.0/24

  Metric: 10     IP 10.0.3.0/24

  Metric: 10     IP 10.0.3.3/30

  Metric: 10     IS-Extended dasher.02172.19.170.0/24

  Metric: 20     IP-Interarea 10.1.1.1/32

    Route Admin Tag: 60

  Metric: 20     IP-Interarea 192.168.0.6/32

    Route Admin Tag: 50

Related Commands

show isis fast-reroute

To display information about Intermediate System-to-Intermediate System (IS-IS) Fast Reroute (FRR) configurations, use the show isis fast-reroute command in user EXEC or privileged EXEC mode.

show isis fast-reroute {interfaces [type number] | summary}

Syntax Description

Command Default

This command has no default settings.

Command Modes

User EXEC (>)
Privileged EXEC (#)

Command History

Usage Guidelines

The show isis fast-reroute interfaces command displays whether or not an interface is supported by a platform.

Examples

The following is sample output from the show isis fast-reroute interfaces command:

Router# show isis fast-reroute interfaces

Tag Null - Fast-Reroute Platform Support Information:

   Serial6/3: Protectable: Yes. Usable for repair: Yes

   Serial6/2: Protectable: Yes. Usable for repair: Yes

   Loopback16: Protectable: No. Usable for repair: No

Table 14 describes the significant fields shown in the display.

The following is sample output from the show isis fast-reroute summary command:

Router# show isis fast-reroute summary 

Prefix Counts:          Total      Protected    Coverage

   High priority:        17         17           100%

   Normal priority:      0          0            0%

Table 15 describes the significant fields shown in the display.

Related Commands

show isis hostname

To display the router-name-to-system-ID mapping table entries for an Intermediate System-to-Intermediate System (IS-IS) router, use the show isis hostname command in privileged EXEC mode.

show isis hostname

Syntax Description

This command has no arguments or keywords.

Command Modes

Privileged EXEC

Command History

Usage Guidelines

In the IS-IS routing domain, the system ID is used to represent each router. The system ID is part of the network entity title (NET) that is configured for each IS-IS router. For example, a router with a configured NET of 49.0001.0023.0003.000a.00 has a system ID of 0023.0003.000a. Router-name-to-system-ID mapping is difficult for network administrators to remember during maintenance and troubleshooting on the routers. Entering the show isis hostname command displays the entries in the router-name-to-system-ID mapping table.

If the dynamic hostname feature has not been disabled by entering the no hostname dynamic command, the mapping will consist of a dynamic host mapping table. However, if the clns host command has been entered to create a mapping between the router name and the system ID, this locally defined mapping will take precedence over the dynamically learned one from the dynamic hostname feature.

Examples

The following example changes the hostname to RouterA and assigns the NET 49.0001.0000.0000.000b.00 to RouterA.

Router> enable

Router# configure terminal

Router(config)# hostname RouterA

RouterA(config)# router isis CompanyA

RouterA(config-router)# net 49.0001.0000.0000.000b.00

RouterA(config-router)# hostname dynamic

RouterA(config-router)# end

Entering the show isis hostname command displays the dynamic host mapping table. The dynamic host mapping table displays the router-name-to-system-ID mapping table entries for Router-b, Router-c and for the local router named Router-a. The command output shows that the local router is running the IS-IS process named CompanyA. The table also shows that the neighbor router Router-b is a Level-1 router, and its hostname is advertised by the Level-1 (L1) link-state protocol (LSP). Router-b is a Level-2 router and its hostname is advertised by the L2 LSP. The * symbol that appears under Level for the local router Router-a signifies that this is the router-name-to-system-ID mapping information for the local router.

Router-a# show isis hostname

Level  System ID      Dynamic Hostname    (CompanyA)

   1   3333.3333.333b Router-b

   2   3131.3131.313b Router-c

   *   3232.3232.323b Router-a

Related Commands

show isis lsp-log

To display the Level 1 and Level 2 Intermediate System-to-Intermediate System (IS-IS) link-state packet (LSP) log of the interfaces that triggered the new LSP, use the show isis lsp-log command in EXEC mode.

show isis lsp-log

Syntax Description

This command has no arguments or keywords.

Command Modes

EXEC

Command History

Examples

The following is sample output from the show isis lsp-log command:

Router# show isis lsp-log

   Level 1 LSP log

  When       Count      Interface   Triggers

07:05:18        3                   CONFIG NEWADJ DIS

07:05:13        2       Ethernet0   NEWADJ DIS

07:04:43        1                   ATTACHFLAG

07:01:38        2       Ethernet0   IPUP

07:01:33        2       Loopback0   CONFIG

07:01:24        1       Ethernet0   DELADJ

07:01:17        2       Ethernet0   DIS ES

07:01:02        1       Ethernet0   NEWADJ

07:00:57        2       Ethernet0   NEWADJ DIS

   Level 2 LSP log

  When       Count      Interface   Triggers

07:05:24        2                   CONFIG NEWADJ

07:05:23        1       Ethernet0   NEWADJ

07:05:18        1       Ethernet0   DIS

07:05:00        1         Serial0   NEWADJ

07:01:44        2       Ethernet0   IPUP

07:01:39        3       Loopback0   CONFIG DELADJ

07:01:30        1       Ethernet0   DELADJ

07:01:25        1         Serial0   NEWADJ

07:00:56        1                   IPIA

07:00:47        2                   AREASET IPIA

Table 16 describes the fields shown in the display.

show isis neighbors

To display information about Intermediate System-to-Intermediate System (IS-IS) neighbors, use the show isis neighbors command in privileged EXEC mode.

show isis neighbors [detail]

Syntax Description

Command Default

Brief information for IS-IS neighbors is displayed.

Command Modes

Privileged EXEC

Command History

Usage Guidelines

The show isis neighbors command is used to display brief information about connected IS-IS routers. Enter the detail keyword to display more detailed information.

Examples

Release 12.0(29)S

The show isis neighbors command is entered to display information about the IS-IS neighbor Router1.

Router5# show isis neighbors

System Id      Type Interface IP Address      State Holdtime Circuit Id

0000.0000.0002 L1   Et0/0     192.168.128.2   UP    21       R5.02              

0000.0000.0002 L2   Et0/0     192.168.128.2   UP    28       R5.02              

Thee show isis neighbors detail command is entered to display more detailed information about the IS-IS neighbor Router1.

Router5# show isis neighbors detail

System Id           Type Interface IP Address      State Holdtime Circuit Id

0000.0000.0002      L1   Et0/0     192.168.128.2   UP    21       R5.02              

  Area Address(es): 49.0001

  SNPA: aabb.cc00.1f00      

  State Changed: 00:00:52

  LAN Priority: 64

  Format: Phase V

0000.0000.0002      L2   Et0/0     192.168.128.2   UP    22       R5.02              

  Area Address(es): 49.0001

  SNPA: aabb.cc00.1f00      

  State Changed: 00:00:52

  LAN Priority: 64

  Format: Phase V

Release 12.2(33)SRB

The show isis neighbors detail command is entered to verify the status of the IS-IS neighbor Router1 for a network that has MTR configured. For each of the topologies - unicast, DATA and VOICE, the interface information is displayed.

Router5# show isis neighbors detail

System Id      Type Interface IP Address      State Holdtime Circuit Id

0000.0000.0005 L2   Et0/0     192.168.128.2   UP    28       R5.01              

  Area Address(es): 33

  SNPA: aabb.cc00.1f00      

  State Changed: 00:07:05

  LAN Priority: 64

  Format: Phase V

  Remote TID:  100, 200

  Local TID:   100, 200

Table 17 describes the significant fields shown in the display.

show isis nsf

To display current state information regarding Intermediate System-to-Intermediate System (IS-IS) Cisco nonstop forwarding (NSF), use the show isis nsf command in user EXEC mode.

show isis nsf

Syntax Description

This command has no arguments or keywords.

Command Modes

User EXEC

Command History

Usage Guidelines

The show isis nsf command can be used with both Cisco proprietary IS-IS NSF and Internet Engineering Task Force (IETF) IS-IS NSF. The information displayed when this command is entered depends on which protocol has been configured. To configure nsf for a specific routing protocol, use the router bgp, router ospf, or router isis commands in global configuration mode.

Examples

The following example shows state information for an active RP that is configured to use Cisco proprietary IS-IS NSF:

Router# show isis nsf

NSF enabled, mode 'cisco'

RP is ACTIVE, standby ready, bulk sync complete

NSF interval timer expired (NSF restart enabled)

Checkpointing enabled, no errors

Local state:ACTIVE,  Peer state:STANDBY HOT,  Mode:SSO

The following example shows state information for a standby RP that is configured to use Cisco proprietary IS-IS NSF:

Router# show isis nsf

NSF enabled, mode 'cisco'

RP is STANDBY, chkpt msg receive count:ADJ 2, LSP 314

NSF interval timer notification received (NSF restart enabled)

Checkpointing enabled, no errors

Local state:STANDBY HOT,  Peer state:ACTIVE,  Mode:SSO

The following example shows state information when the networking device is configured to use IETF IS-IS NSF:

Router# show isis nsf 

NSF is ENABLED, mode IETF 

NSF pdb state:Inactive

NSF L1 active interfaces:0

NSF L1 active LSPs:0

NSF interfaces awaiting L1 CSNP:0

Awaiting L1 LSPs:

NSF L2 active interfaces:0

NSF L2 active LSPs:0

NSF interfaces awaiting L2 CSNP:0

Awaiting L2 LSPs:

Interface:Serial3/0/2

    NSF L1 Restart state:Running

    NSF p2p Restart retransmissions:0

    Maximum L1 NSF Restart retransmissions:3

    L1 NSF ACK requested:FALSE

    L1 NSF CSNP requested:FALSE

    NSF L2 Restart state:Running

    NSF p2p Restart retransmissions:0

    Maximum L2 NSF Restart retransmissions:3

    L2 NSF ACK requested:FALSE

Interface:GigabitEthernet2/0/0

    NSF L1 Restart state:Running

    NSF L1 Restart retransmissions:0

    Maximum L1 NSF Restart retransmissions:3

    L1 NSF ACK requested:FALSE

    L1 NSF CSNP requested:FALSE

    NSF L2 Restart state:Running

    NSF L2 Restart retransmissions:0

    Maximum L2 NSF Restart retransmissions:3

    L2 NSF ACK requested:FALSE

    L2 NSF CSNP requested:FALSE

Related Commands

show isis rib

To display paths for a specific route or for all routes under a major network that are stored in the IP local Routing Information Base (RIB), use the show isis rib command in privileged EXEC mode.

show isis rib [ip-address | ip-address-mask]

Syntax Description

Command Default

If no ip-address or ip-address-mask argument is specified, all routes in the Integrated Intermediate System-to-Intermediate System (IS-IS) local RIB will be displayed.

Command Modes

Privileged EXEC

Command History

Usage Guidelines

To verify that an IP prefix update that exists in the IP global RIB also has been updated in the IS-IS local RIB, enter the show isis rib command.

Examples

The following is sample output from the show isis rib command to show all routes under the major network with the IP address mask 10.2.2.0 255.255.255.0 that are stored within the IS-IS local RIB:

Router# show isis rib 10.2.2.0 255.255.255.0

IPv4 local RIB for IS-IS process

10.2.2.0/24 

 [115/L2/20} via 10.2.2.2(Ethernet2), from 10.22.22.22, tag 0, LSP[10/10]

Table 18 describes the significant fields shown in the display.

Related Commands

show isis rib redistribution

To display the prefixes in the local redistribution cache, use the show isis rib redistribution command in user EXEC or privileged EXEC mode.

show isis rib redistribution [level-1 | level-2] [network-prefix]

Syntax Description

Command Modes

User EXEC
Privileged EXEC

Command History

Usage Guidelines

You can use the show isis rib redistribution command to verify that desired routes have been redistributed into Intermediate System-to-Intermediate System (IS-IS). The command output will show the network prefixes in the local redistribution cache.

Examples

In the following example, the output from the show isis rib redistribution command verifies that Internet Protocol version 4 (IPv4) routes have been redistributed into IS-IS. The output is self-explanatory.

Router# show isis rib redistribution

IPv4 redistribution RIB for IS-IS process 

====== Level 1 ======

10.3.3.0/24

  [Connected/0] external 

10.0.18.48/28

  [Connected/0] external 

====== Level 2 ======

The following lines indicate that the prefix 10.3.3.0 with a mask 24 was redistributed from the connected routing protocol into IS-IS as a level 1 route, cost 0, with a metric type external:

10.3.3.0/24

  [Connected/0] external 

The following lines show that the connected routing protocol owns the prefix 10.0.18.48 and that the metric for the route is 28:

10.0.18.48/28

  [Connected/0] external 

Related Commands

show isis spf-log

To display how often and why the router has run a full shortest path first (SPF) calculation, use the show isis spf-log user command in user EXEC or privileged EXEC mode.

show isis [area-tag] [ipv6 | *] spf-log

Syntax Description

Command Modes

User EXEC
Privileged EXEC

Command History

Examples

The following is sample output from the show isis spf-log command with the optional ipv6 keyword:

Router# show isis ipv6 spf-log

                   IPv6 Level 1 SPF log

  When   Duration  Nodes  Count     Last trigger LSP   Triggers

00:15:46    3124     40      1          milles.00-00  TLVCODE

00:15:24    3216     41      5          milles.00-00  TLVCODE NEWLSP

00:15:19    3096     41      1          deurze.00-00  TLVCODE

00:14:54    3004     41      2          milles.00-00  ATTACHFLAG LSPHEADER

00:14:49    3384     41      1          milles.00-01  TLVCODE

00:14:23    2932     41      3          milles.00-00  TLVCODE

00:05:18    3140     41      1                        PERIODIC

00:03:54    3144     41      1          milles.01-00  TLVCODE

00:03:49    2908     41      1          milles.01-00  TLVCODE

00:03:28    3148     41      3           bakel.00-00  TLVCODE TLVCONTENT

00:03:15    3054     41      1          milles.00-00  TLVCODE

00:02:53    2958     41      1          mortel.00-00  TLVCODE

00:02:48    3632     41      2          milles.00-00  NEWADJ TLVCODE

00:02:23    2988     41      1          milles.00-01  TLVCODE

00:02:18    3016     41      1          gemert.00-00  TLVCODE

00:02:14    2932     41      1           bakel.00-00  TLVCONTENT

00:02:09    2988     41      2           bakel.00-00  TLVCONTENT

00:01:54    3228     41      1          milles.00-00  TLVCODE

00:01:38    3120     41      3            rips.03-00  TLVCONTENT

Table 19 describes the significant fields shown in the display.

Table 20 lists possible triggers of a full SPF calculation.

show isis topology

To display a list of all connected routers in all areas, use the show isis topology command in user EXEC or privileged EXEC mode.

show isis [process-tag] [ipv6 | *] topology

Syntax Description

Command Modes

User EXEC (>)
Privileged EXEC (#)

Command History

Usage Guidelines

Use the show isis topology EXEC command to verify the presence and connectivity between all routers in all areas.

Examples

The following example shows output from the show isis topology command using the optional ipv6 keyword. The command shown is used in a dual CLNS-IP network:

Router# show isis ipv6 topology

Tag L2BB:

IS-IS IPv6 paths to level-1 routers

System Id       Metric  Next-Hop        Interface       SNPA

0000.0000.0005 --

0000.0000.0009  10      0000.0000.0009  Tu529           *Tunnel*        

0000.0000.0017  20      0000.0000.0009  Tu529           *Tunnel*        

0000.0000.0053  30      0000.0000.0009  Tu529           *Tunnel*        

0000.0000.0068  20      0000.0000.0009  Tu529           *Tunnel*        

IS-IS paths to level-2 routers

System Id       Metric  Next-Hop        Interface       SNPA

0000.0000.0005  --

0000.0000.0009  10      0000.0000.0009  Tu529           *Tunnel*        

0000.0000.0017  20      0000.0000.0009  Tu529           *Tunnel*        

0000.0000.0053  30      0000.0000.0009  Tu529           *Tunnel*        

0000.0000.0068  20      0000.0000.0009  Tu529           *Tunnel* 

Tag A3253-01:

IS-IS paths to level-1 routers

System Id       Metric  Next-Hop        Interface       SNPA

0000.0000.0003  10      0000.0000.0003  Et1             0000.0c03.6944  

0000.0000.0005  --

0000.0000.0053  10      0000.0000.0053  Et1             0060.3e58.ccdb  

Tag A3253-02:

IS-IS paths to level-1 routers

System Id       Metric  Next-Hop        Interface       SNPA

0000.0000.0002  10      0000.0000.0002  Et2             0000.0c03.6bc5  

0000.0000.0005  --

0000.0000.0053  10      0000.0000.0053  Et2             0060.3e58.ccde 

Table 21 describes the significant fields shown in the display.

snmp-server enable traps isis

To enable Simple Network Management Protocol (SNMP) notifications for Intermediate System-to-Intermediate System (IS-IS) errors and transition state changes, use the snmp-server enable traps isis command in global configuration mode. To disable all or some of the IS-IS SNMP notifications, use the no form of this command.

snmp-server enable traps isis [errors [error-type]] [state-change [state-change-type]]