Cisco IOS IP Routing: ISIS Command Reference
Integrated IS-IS Commands: L through V
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Integrated IS-IS Commands: L through V

Contents

Integrated IS-IS Commands: L through V

log-adjacency-changes (IS-IS)

To configure the router to send a syslog message when an Intermediate System to Intermediate System (IS-IS) 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 [all]

no log-adjacency-changes [all]

Syntax Description

all

(Optional) Includes changes generated by non-IIH (IS-IS Hello) event.

Command Default

This feature is disabled.

Command Modes


Router configuration (config-router)

Command History

Release

Modification

10.3T

This command was introduced.

12.2(28)SB

This command was integrated into Cisco IOS Release 12.2(28)SB.

12.2SX

This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.

Usage Guidelines

This command allows you to know about IS-IS neighbors going up or down. The log-adjacency-changes command is on by default but only changes generated by IIH events are included, unless the all keyword is also used.

Examples

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

Device# enable
Device# configure terminal
Device(config)# router isis ABCD
Device(config-router)# log-adjacency-changes all

Related Commands

Command

Description

show isis neighbors

Displays information about IS-IS neighbors.

show isis topology

Displays IS-IS paths to Intermediate Systems.

lsp-full suppress

To control which routes are suppressed when the link-state protocol data unit (PDU) becomes full, use the lsp-full suppresscommand 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

external

Suppresses any redistributed routes on this router.

interlevel

Suppresses any routes coming from the other level. For example, if the Level-2 LSP becomes full, routes from Level 1 are suppressed.

none

Suppresses no routes.

Command Default

Redistributed routes are suppressed.

Command Modes


Router configuration (config-router)

Command History

Release

Modification

12.0(25)S

This command was introduced.

12.2(18)S

This command was integrated into Cisco IOS Release 12.2(18)S.

12.3(4)T

This command was integrated into Cisco IOS Release 12.3(4)T.

12.2(27)SBC

This command was integrated into Cisco IOS Release 12.2(27)SBC.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2SX

This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.

Cisco IOS XE Release 2.1

This command was introduced on Cisco ASR 1000 Series Aggregation Services Routers.

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

Command

Description

clear isis lsp-full

Clears the LSPFULL state.

redistribute maximum-prefix

Limits the number of prefixes redistributed into IS-IS or generates a warning when the number of prefixes redistributed into IS-IS reaches a maximum.

lsp-gen-interval (IPX)

To set the minimum interval at which link-state packets (LSPs) are generated, use the lsp-gen-intervalcommand 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

seconds

Minimum interval, in seconds. It can be a number in the range 0 to 120. The default is 5 seconds.

Command Default

5 seconds

Command Modes


Router configuration

Command History

Release

Modification

10.3

This command was introduced.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2SX

This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.

Usage Guidelines

The lsp-gen-intervalcommand 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

Command

Description

ipx router

Specifies the routing protocol to use.

spf-interval

Controls how often Cisco IOS software performs the SPF calculation.

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

level-1

(Optional) Apply intervals to Level-1 areas only.

level-2

(Optional) Apply intervals to Level-2 areas only.

lsp-max-wait

Indicates the maximum interval (in seconds) between two consecutive occurrences of an LSP being generated. The range is 1 to 120 seconds. The default is 5 seconds.

lsp-initial-wait

(Optional) Indicates the initial LSP generation delay (in milliseconds). The range is 1 to 120,000 milliseconds. The default is 50 milliseconds.

lsp-second-wait

(Optional) Indicates the hold time between the first and second LSP generation (in milliseconds). The range is 1 to 120,000 milliseconds. The default is 5000 milliseconds (5 seconds).

Command Default

lsp-max-wait : 5 secondslsp-initial-wait: 50 millisecondslsp-second-wait: 5000 milliseconds

Command Modes


Router configuration (config-router)

Command History

Release

Modification

12.1

This command was introduced.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2SX

This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.

15.1(2)S

This command was integrated into Cisco IOS Release 15.1(2)S.

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

Command

Description

isis lsp-interval

Sets the time delay between successive IS-IS LSP transmissions.

isis retransmit-interval

Sets the amount of time between retransmission of each IS-IS LSP on a point-to-point link.

isis retransmit-throttle-interval

Sets the minimum delay between retransmissions on each LSP on a point-to-point interface.

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

seconds

Interval (in seconds) at which LSPs are refreshed.The range is 1 to 65535 seconds. The default value is 900 seconds (15 minutes).

Command Default

900 seconds (15 minutes)

Command Modes


Router configuration

Command History

Release

Modification

10.3

This command was introduced.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2SX

This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.

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

Command

Description

max-lsp-lifetime (IS-IS)

Sets the maximum time that link-state packets (LSPs) can remain in a router’s database without being refreshed.

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

number

Number of manual addresses to add. The range is from 3 to 234. There is no default value.

Command Default

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

Command Modes


Router configuration

Command History

Release

Modification

10.0

This command was introduced.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2SX

This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.

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

Command

Description

net

Assigns a NET address to an IS-IS router.

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

default-value

Metric value to be assigned to the link and used to calculate the path cost via the links to destinations. You can configure this metric for Level 1 or Level 2 routing only. For style wide metrics the range is from 1 to 16777214. For style narrow metrics the range is from 1 to 63.

level-1

(Optional) Set IS-IS Level-1 IPv4 or IPv6 metric.

level-2

(Optional) Set IS-IS Level-2 IPv4 or IPv6 metric.

Command Default

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

Release

Modification

12.3(4)T

This command was introduced.

12.0(27)S

This command was integrated into Cisco IOS Release 12.0(27)S.

12.2(25)S

This command was integrated into Cisco IOS Release 12.2(25)S.

12.2(18)SXE

This command was integrated into Cisco IOS Release 12.2(18)SXE.

12.2(27)SBC

This command was integrated into Cisco IOS Release 12.2(27)SBC.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

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 metriccommand 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 interfacecommand 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 metriccommand 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

Command

Description

isis ipv6 metric

Configures the value of an IS-IS IPv6 metric.

isis metric

Configures the metric for an interface.

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

transition

(Optional) Instructs the router to accept both old- and new-style TLVs.

level-1

(Optional) Enables this command on routing level 1.

level-2

(Optional) Enables this command on routing level 2.

level-1-2

(Optional) Enables this command on routing levels 1 and 2.

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

Release

Modification

12.0(5)S

This command was introduced.

12.2(28)SB

This command was integrated into Cisco IOS Release 12.2(28)SB.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2SX

This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release train depends on your feature set, platform, and platform hardware.

Cisco IOS XE Release 2.1

This command was implemented on Cisco ASR 1000 Series Aggregation Services Routers.

15.1(2)S

This command was integrated into Cisco IOS Release 15.1(2)S.

15.2(3)T

This command was integrated into Cisco IOS Release 15.2(3)T.

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

Command

Description

metric-style narrow

Configures a router to generate and accept old-style TLVs.

metric-style transition

Configures a router to generate and accept both old-style and new-style TLVs.

microloop avoidance

To enable local microloop avoidance, use the microloop avoidance command in router configuration mode. To remove this configuration, use the no form of this command.

microloop avoidance [ disable | protected ]

no microloop avoidance [ disable | protected ]

Syntax Description

disable

(Optional) Disables microloop avoidance in topologies where it is automatically enabled.

protected

(Optional) Enables microloop avoidance only for prefixes that have valid backup paths.

Command Default

Microloop avoidance is disabled when remote loop-free alternate (RLFA) is not configured but is enabled for protected prefixes when RLFA is configured.

Command Modes

Router configuration (router-config)

Command History

Release Modification

Cisco IOS XE Release 3.11S

This command was introduced.

15.4(1)S

This command was integrated into Cisco IOS Release 15.4(1)S.

Usage Guidelines

When RLFA is enabled, microloop avoidance is enabled by default with the protected keyword enabled and a default delay of 5000 ms. This automatic enabling affects the operational state of the device but not the configured state. Therefore, this state is not reflected in the output of the show running-config command.

Examples

When RLFA is enabled, microloop avoidance is enabled by default. The following example shows how to disable microloop avoidance when RLFA is enabled.

Device> enable
Device# configure terminal
Device(config)# router isis test
Device(config-router)# microloop avoidance disable
Device(config-router)# end

Related Commands

Command

Description

microloop avoidance rib-update-delay

Configures a RIB-update delay value to avoid microloops.

show running-config

Displays contents of the currently running configuration file.

microloop avoidance rib-update-delay

To configure a Routing Information Base (RIB) update delay value to avoid microloops in a network, use the microloop avoidance rib-update-delay command in router configuration mode. To remove this configuration, use the no form of this command.

microloop avoidance [ rib-update-delay delay-time ]

no microloop avoidance [ rib-update-delay ]

Syntax Description

delay-time

(Optional) Delay time in milliseconds. The range is from 1-60000.

Command Default

A RIB update delay value is not configured.

Command Modes

Router configuration (router-config)

Command History

Release Modification

Cisco IOS XE Release 3.11S

This command was introduced.

15.4(1)S

This command was integrated into Cisco IOS Release 15.4(1)S.

Usage Guidelines

Use this command to enable a device to delay updating its forwarding table in order to avoid traffic from microlooping between devices connected to a failed link.

Examples

The following example shows how configure a RIB update delay value.

Device> enable
Device# configure terminal
Device(config)# router isis test
Device(config-router)# microloop avoidance rib-update-delay 6000
Device(config-router)# end

Related Commands

Command

Description

microloop avoidance

Enables local microloop avoidance.

show running-config

Displays contents of the currently running configuration file.

net

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

net network-entity-title

no net network-entity-title

Syntax Description

network-entity-title

Area address and the system ID for a CLNS routing process.

Command Default

The defaults are as follows:
  • No NET is configured.
  • The IS-IS process is disabled.

Command Modes


Router configuration (config-router)

Command History

Release

Modification

10.0

This command was introduced.

12.0(5)T

This command was modified to include multiarea IS-IS routing.

15.1(2)S

This command was integrated into Cisco IOS Release 15.1(2)S.

Usage Guidelines

Under most circumstances, one and only one NET must be configured.

A NET is a network service access point (NSAP) where the last byte is always zero. On a Cisco router running IS-IS, a NET can be 8 to 20 bytes. The last byte is always the n-selector and must be zero.

The six bytes directly in front of the n-selector are the system ID. The system ID length is a fixed size and cannot be changed. The system ID must be unique throughout each area (Level 1) and throughout the backbone (Level 2).

All bytes in front of the system ID are the area ID.

Even when IS-IS is used to perform IP routing only (no CLNS routing enabled), a NET must still be configured to define the router system ID and area ID.

A maximum of three NETs per router are allowed. In rare circumstances, it is possible to configure two or three NETs. In such a case, the area this router is in will have three area addresses. There will still be only one area, but it will have an additional maximum of three area addresses.

Configuring multiple NETs can be temporarily useful in the case of network reconfiguration where multiple areas are merged, or where one area is split into additional areas. Multiple area addresses enable you to renumber an area individually as needed.

If you are configuring multiarea IS-IS, the area ID must be unique, but the system ID portion of the NET must be the same for all IS-IS routing process instances.

Examples

The following example configures a router with system ID 0000.0c11.1111.00 and area ID 47.0004.004d.0001:

router isis CHESNUT
 net 47.0004.004d.0001.0001.0c11.1111.00

The following example shows three IS-IS routing processes with three areas 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

Related Commands

Command

Description

is-type

Configures the routing level for an instance of the IS-IS routing process.

router isis

Enables the IS-IS routing protocol and specifies an IS-IS process.

show isis topology

Displays a list of all connected routers in all areas.

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

area-tag

Meaningful name for a routing process. If it is not specified, a null tag is assumed and the process is referenced with a null tag. This name must be unique among all IP or Connectionless Network Service Protocol (CLNS) router processes for a given router.

Required for multiarea IS-IS configuration. Optional for conventional IS-IS configuration.

Command Default

This command is disabled by default.

Command Modes


Router configuration

Command History

Release

Modification

12.0(5)T

This command was introduced.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2SX

This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.

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

Command

Description

is-type

Configures the routing level for an instance of the IS-IS routing process.

router isis

Enables the IS-IS routing protocol and specifies an IS-IS process.

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

prc-max-wait

Indicates the maximum interval (in seconds) between two consecutive PRC calculations. Value range is 1 to 120 seconds. The default is 5 seconds.

prc-initial-wait

(Optional) Indicates the initial PRC calculation delay (in milliseconds) after a topology change. The range is 1 to 120,000 milliseconds. The default is 2000 milliseconds.

prc-second-wait

(Optional) Indicates the hold time between the first and second PRC calculation (in milliseconds). The range is 1 to 120,000 milliseconds. The default is 5000 milliseconds (5 seconds).

Command Default

prc-max-wait : 5 secondsprc-initial-wait: 2000 millisecondsprc-second-wait: 5000 milliseconds

Command Modes


Router configuration (config-router)

Command History

Release

Modification

12.1

This command was introduced.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2SX

This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.

15.1(2)S

This command was integrated into Cisco IOS Release 15.1(2)S.

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.

Command Default

No default behavior or values

Command Modes


Router configuration

Command History

Release

Modification

12.3(4)T

This command was introduced.

12.0(27)S

This command was integrated into Cisco IOS Release 12.0(27)S.

12.2(25)S

This command was integrated into Cisco IOS Release 12.2(25)S.

12.2(18)SXE

This command was integrated into Cisco IOS Release 12.2(18)SXE.

12.2(27)SBC

This command was integrated into Cisco IOS Release 12.2(27)SBC.

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

Command

Description

isis protocol shutdown

Disables the IS-IS protocol so that it cannot form adjacencies on a specified interface and places the IP address of the interface into the LSP that is generated by the router.

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 isiscommand 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

ip

Redistributes IS-IS IP routes (IS-IS Connectionless Network Service (CLNS) routes are unaffected).

level-1 | level-2

Level from which and to which you are redistributing IS-IS routes.

into

Keyword that separates the level of routes being redistributed from the level into which you are redistributing routes.

distribute-list list-number

(Optional) Number of a distribute list that controls the IS-IS redistribution. You may specify either a distribute list or a route map, but not both.

route-map map-tag

(Optional) Name of a route map that controls the IS-IS redistribution. You may specify either a distribute list or a route map, but not both.

Command Default

There are no default values for this command.

Command Modes


Router configuration (config-router)#

Command History

Release

Modification

12.0(5)T

This command was introduced.

12.3(2)T

The route-map map-tag keyword and argument were added.

12.2(27)SBC

This command was integrated into Cisco IOS Release 12.2(27)SBC.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2SX

This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.

Cisco IOS XE Release 3.6S

This command was integrated into Cisco IOS XE Release 3.6S

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 widecommand 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

Command

Description

ipv6 route priorityhigh

Assigns a high priority to an IS-IS IPv6 prefix.

isis ipv6 tag

Configures an administrative tag value that will be associated with an IPv6 address prefix and applied to an IS-IS link-state packet (LSP).

metric-style wide

Configures a router running IS-IS so that it generates and accepts only new-style type, length, and value.

show isis database verbose

Displays additional information about the IS-IS database.

summary-prefix (IPv6 IS-IS)

Creates aggregate IPv6 prefixes for IS-IS.

redistribute isis (IPv6)

To redistribute IPv6 routes from one routing domain into another routing domain using Intermediate System-to-Intermediate System (IS-IS) as both the target and source protocol, use the redistribute isis command in address family configuration mode. To disable redistribution, use the no form of this command.

redistribute isis [process-id] { level-1 | level-2 } into { level-1 | level-2 } { distribute-list | | list-name | | route-map | | map-tag }

no redistribute isis [process-id] { level-1 | level-2 } into { level-1 | level-2 } { distribute-list | | list-name | | route-map | map-tag }

Syntax Description

process-id

(Optional) A tag value that defines a meaningful name for a routing process. You can specify only one IS-IS process per router. Creating a name for a routing process means that you use names when configuring routing.

level-1

Specifies that IS-IS Level 1 routes are redistributed into other IP routing protocols independently.

level-2

Specifies that IS-IS Level 2 routes are redistributed into other IP routing protocols independently.

into

Distributes IS-IS Level 1 or Level 2 routes into Level 1 or Level 2 in another IS-IS instance.

distribute-list

Specifies the distribute list used for the redistributed route.

list-name

Specifies the name of the distribute list for the redistributed route.

route-map map-tag

(Optional) Specifies the name of a route map that controls the IS-IS redistribution. You can specify either a distribute list or a route map, but not both.

Command Default

Route redistribution is disabled. No process ID is defined.

Command Modes


Address family configuration (config-router-af)

Command History

Release

Modification

12.2(15)T

This command was introduced.

12.2(25)SG

This command was integrated into Cisco IOS Release 12.2(25)SG.

Cisco IOS XE Release 2.4

This command was introduced on Cisco ASR 1000 Aggregation Services Routers.

Cisco IOS XE Release 3.6S

This command was modified. Support for the route-map keyword was introduced.

Usage Guidelines

Changing or disabling any keyword will not affect the state of other keywords.

A router receiving an IPv6 IS-IS route with an internal metric will consider the cost of the route from itself to the redistributing router plus the advertised cost to reach the destination. An external metric considers only the advertised metric to reach the destination.

IS-IS will ignore any configured redistribution of routes configured with the connected keyword. IS-IS will advertise a prefix on an interface if either IS-IS is running over the interface or the interface is configured as passive.

Routes learned from IPv6 routing protocols can be redistributed into IPv6 IS-IS at Level 1 into an attached area or at Level 2. The level-1-2 keyword allows both Level 1 and Level 2 routes in a single command.

Examples

The following example shows how to redistribute only Level-1 routes with tag 100 to Level 2:

router isis
address-family ipv6
redistribute isis level-1 into level-2 route-map match-tag
route-map match-tag
match tag 100

Related Commands

Command

Description

default-metric

Specifies a default metric for redistributed routes.

ipv6 route priority high

Assigns a high priority to an IS-IS IPv6 prefix.

isis ipv6 tag

Configures an administrative tag value that will be associated with an IPv6 address prefix and applied to an IS-IS LSP.

metric-style wide

Configures a router running IS-IS so that it generates and accepts only new-style type, length, and value.

redistribute (IPv6)

Redistributes IPv6 routes from one routing domain into another routing domain.

show isis database verbose

Displays details about the IS-IS link-state database, including the route tag.

summary-prefix (IPv6 IS-IS)

Creates aggregate IPv6 prefixes for IS-IS.

router isis

To enable the Intermediate System-to-Intermediate System (IS-IS) routing protocol and to specify an IS-IS process, use t he router isis command in global configuration mode. To disable IS-IS routing, use the noform of this command.

router isis [area-tag]

no router isis [area-tag]

Syntax Description

area-tag

(Optional) Required for multiarea IS-IS configuration. Optional for conventional IS-IS configuration.

Meaningful name for a routing process. If it is not specified, a null tag is assumed and the process is referenced with a null tag. This name must be unique among all IP or Connectionless Network Service (CLNS) router processes for a given router.

Command Default

This command is disabled by default.

Command Modes


Global configuration (config)

Command History

Release

Modification

10.0

This command was introduced.

12.0(5)T

This command was modified. Multiarea functionality was added to change the way the area-tag argument is used.

12.2(28)SB

This command was integrated into Cisco IOS Release 12.2(28)SB.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2SX

This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.

Cisco IOS XE Release 2.1

This command was integrated into Cisco IOS XE Release 2.1 and implemented on Cisco ASR 1000 Series Aggregation Services Routers.

15.1(2)S

This command was integrated into Cisco IOS Release 15.1(2)S.

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

Command

Description

clns router isis

Enables IS-IS routing for ISO CLNS on an interface and attaches an area designator to the routing process.

ip router isis

Configures an IS-IS routing process for IP on an interface and attaches an area designator to the routing process.

is-type

Configures the routing level for an IS-IS routing process.

net

Configures an IS-IS NET for the routing process.

redistribute (IP)

Redistributes routes from one routing domain into another routing domain.

route-map (IP)

Defines the conditions for redistributing routes from one routing protocol into another.

set-attached-bit

To s pecify constraints for when a Level 1 - Level 2 (L1L2) router should set its attached-bit, use the set-attached-bitcommand 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

route-map map-tag

Identifier of a configured route map. If the specified route map is matched, the router continues to set its attached-bit.

Command Default

This command is disabled by default.

Command Modes


Router configuration

Command History

Release

Modification

12.2

This command was introduced.

12.2(4)B

This command was integrated into Cisco IOS Release 12.2(4)B.

12.2(14)S

This command was integrated into Cisco IOS Release 12.2(14)S.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2SX

This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.

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

Command

Description

route-map

Defines the conditions for redistributing routes from one routing protocol into another.

show clns route

Displays one or all of the destinations to which a router knows how to route CLNS packets.

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 noform of this command.

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

no set-overload-bit

Syntax Description

on-startup

(Optional) Sets the overload bit upon the system starting up. The overload bit remains set for the number of seconds configuredor until BGP has converged, depending on the subsequent argument or keyword specified.

seconds

(Optional) When the on-startup keyword is configured, causes the overload bit to be set upon system startup and remain set for the specified number of seconds. The range is from 5 to 86400 seconds.

wait-for-bgp

(Optional) When the on-startup keyword is configured, causes the overload bit to be set upon system startup and remain set until BGP has converged.

suppress

(Optional) Causes the type of prefix identified by the subsequent keyword or keywords to be suppressed.

interlevel

(Optional) When the suppress keyword is configured, prevents the IP prefixes learned from another IS-IS level from being advertised.

external

(Optional) When the suppress keyword is configured, prevents the IP prefixes learned from other protocols from being advertised.

Command Default

The overload bit is not set.

Command Modes


Router configuration

Command History

Release

Modification

11.2

This command was introduced.

11.3(2)

The on-startup keyword and the seconds argument were added.

12.0(7)S

The wait-for-bgp keyword was added.

12.1(9)

The wait-for-bgp keyword was added.

12.2(2)

The wait-for-bgp keyword was added.

12.0(21)ST

The suppress, interlevel,and externalkeywords were added.

12.2(8)

The suppress, interlevel,and externalkeywords were added.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2SX

This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.

15.1(2)S

This command was integrated into Cisco IOS Release 15.1(2)S.

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

type

(Optional) Interface type.

number

(Optional) Interface number.

Command Modes


Privileged EXEC

Command History

Mainline Release

Modification

10.0

This command was introduced.

0S Release

12.0(31)S

Support for the BFD feature was added.

S Release

12.2(18)SXE

Support for the Bidirectional Forwarding Detection (BFD) feature was added.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

T Release

12.4(4)T

Support for the BFD feature was added.

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

Examples

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

The table below describes the significant fields shown in the display.

Table 1 show clns interface Field Descriptions

Field

Description

TokenRing 0 is administratively down, line protocol is down

(First interface). Shown to be administratively down with CLNS disabled.

TokenRing 1 is up, line protocol is up

(Second interface). Shown to be up, and the line protocol is up.

Serial 2 is up, line protocol is up

(Third interface). Shown to be up, and the line protocol is up.

Checksums enabled

Can be enabled or disabled.

MTU

The number following maximum transmission unit (MTU) is the maximum transmission size for a packet on this interface.

Encapsulation

Describes the encapsulation used by CLNP packets on this interface.

ERPDUs

Displays information about the generation of error protocol data units (ERPDUs). They can be either enabled or disabled. If they are enabled, they are sent out no more frequently than the specified interval.

RDPDUs

Provides information about the generation of redirect protocol data units (RDPDUs). They can be either enabled or disabled. If they are enabled, they are sent out no more frequently than the specified interval. If the address mask is enabled, redirects are sent out with an address mask.

Congestion Experienced

Tells when CLNS will turn on the congestion experienced bit. The default is to turn this bit on when there are more than four packets in a queue.

CLNS fast switching

Displays whether fast switching is supported for CLNS on this interface.

DEC compatibility mode

Indicates whether Digital Equipment Corporation (DEC) compatibility has been enabled.

CLNS cluster alias enabled on this interface

Indicates that CLNS cluster aliasing has been enabled on this interface.

Next ESH/ISH

Displays when the next end system (ES) hello or intermediate system (IS) hello will be sent on this interface.

Routing Protocol

Lists the areas that this interface is in. In most cases, an interface will be in only one area.

Circuit Type

Indicates whether the interface has been configured for local routing (level 1), area routing (level 2), or local and area routing (level 1-2).

Interface number, local circuit ID Level-1 Metric DR ID Level-1 IPv6 Metric Number of active level-1 adjacencies Level-2 Metric DR ID Level-2 IPv6 Metric Number of active level-2 adjacencies Next IS-IS LAN Level-1 Next IS-IS LAN Level-2

Last series of fields displays information pertaining to the International Organization for Standardization (ISO) CLNS routing protocols enabled on the interface. For ISO Interior Gateway Routing Protocol (IGRP), the routing domain and area addresses are specified. For IS-IS, the Level 1 and Level 2 metrics, priorities, circuit IDs, and number of active Level 1 and Level 2 adjacencies are specified.

BFD enabled

BFD has been enabled on the interface.

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

area-tag

Required for multiarea IS-IS configuration. Optional for conventional IS-IS configuration.

Meaningful name for a routing process. This name must be unique among all IP or CLNS router processes for a given router. If an area tag is not specified, a null tag is assumed and the process is referenced with a null tag. If an area tag is specified, output is limited to the specified area.

type

(Optional) Interface type.

number

(Optional) Interface number.

detail

(Optional) When specified, the areas associated with the intermediate systems are displayed. Otherwise, a summary display is provided.

Command Modes


EXEC

Command History

Release

Modification

10.0

This command was introduced.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

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

The table below describes significant fields shown in the display.

Table 2 show clns is-neighbors Field Descriptions

Field

Descriptions

System Id

Identification value of the system.

Interface

Interface on which the router was discovered.

State

Adjacency state. Up and Init are the states. See the show clns neighbors description.

Type

L1, L2, and L1L2 type adjacencies. See the show clns neighbors description.

Priority

IS-IS priority that the respective neighbor is advertising. The highest priority neighbor is elected the designated IS-IS router for the interface.

Circuit Id

Neighbor’s idea of what the designated IS-IS router is for the interface.

Format

Indicates if the neighbor is either a Phase V (OSI) adjacency or Phase IV (DECnet) adjacency.

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

Command

Description

clear clns is-neighbors

Removes IS neighbor information from the adjacency database.

clns is-neighbor

Defines all intermediate systems that will be used when you manually specify the NSAP-to-SNPA mapping.

show clns traffic

To list the Connectionless Network Service (CLNS) packets that this router has seen, use the show clns traffic command in privileged EXEC mode.

show clns area-tag traffic [ since { bootup | show } ]

Syntax Description

area-tag

(Required for multiarea Intermediate System to Intermediate System (IS-IS) configuration. Optional for conventional IS-IS configuration.) Meaningful name for a routing process. This name must be unique among all IP or CLNS router processes for a given router. If an area tag is not specified, a null tag is assumed and the process is referenced with a null tag. If an area tag is specified, output is limited to the specified area.

since

(Optional) Displays the CLNS protocol statistics since bootup or the last time the statistics was displayed.

bootup

Displays the CLNS protocol statistics since bootup.

show

Displays the CLNS protocol statistics since the last time the statistics was displayed.

Command Modes


Privileged EXEC (#)

Command History

Release

Modification

10.0

This command was introduced.

12.2(9)T

The since, bootup,and showkeywords were introduced.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

Examples

The following sample output from the show clns trafficcommand lists all the CLNS packets it has seen:

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

The table below describes the significant fields shown in the display.

Table 3 show clns traffic Field Descriptions

Field

Description

CLNS & ESIS Output

Total number of packets that this router has sent.

Input

Total number of packets that this router has received.

CLNS Local

Lists the number of packets that were generated by this router.

Forward

Lists the number of packets that this router has forwarded.

CLNS Discards

Lists the packets that CLNS has discarded, along with the reason for the discard.

CLNS Options

Lists the options seen in CLNS packets.

CLNS Segments

Lists the number of packets segmented and the number of failures that occurred because a packet could not be segmented.

CLNS Broadcasts

Lists the number of CLNS broadcasts sent and received.

Echos

Lists the number of echo request packets and echo reply packets received. The line following this field lists the number of echo request packets and echo reply packets sent.

ESIS (sent/rcvd)

Lists the number of End System Hello (ESH), Intermediate System Hello (ISH), and redirects sent and received.

ISO IGRP

Lists the number of ISO Interior Gateway Routing Protocol (IGRP) queries and updates sent and received.

Router Hellos

Lists the number of ISO IGRP router hello packets sent and received.

IS-IS: Level-1 hellos (sent/rcvd)

Lists the number of Level 1 IS-IS hello packets sent and received.

IS-IS: Level-2 hellos (sent/rcvd)

Lists the number of Level 2 IS-IS hello packets sent and received.

IS-IS: PTP hellos (sent/rcvd)

Lists the number of point-to-point IS-IS hello packets sent and received over serial links.

IS-IS: Level-1 LSPs (sent/rcvd)

Lists the number of Level 1 link-state Protocol Data Unit (PDUs) sent and received.

IS-IS: Level-2 LSPs (sent/rcvd)

Lists the number of Level 2 link-state PDUs sent and received.

IS-IS: Level-1 CSNPs (sent/rcvd)

Lists the number of Level 1 Complete Sequence Number Packets (CSNP) sent and received.

IS-IS: Level-2 CSNPs (sent/rcvd)

Lists the number of Level 2 CSNPs sent and received.

IS-IS: Level-1 PSNPs (sent/rcvd)

Lists the number of Level 1 Partial Sequence Number Packets (PSNP) sent and received.

IS-IS: Level-2 PSNPs (sent/rcvd)

Lists the number of Level 2 PSNPs sent and received.

IS-IS: Level-1 DR Elections

Lists the number of times Level 1 designated router election occurred.

IS-IS: Level-2 DR Elections

Lists the number of times Level 2 designated router election occurred.

IS-IS: Level-1 SPF Calculations

Lists the number of times the Level 1 shortest-path-first (SPF) tree was computed.

IS-IS: Level-2 SPF Calculations

Lists the number of times the Level 2 SPF tree was computed.

Related Commands

Command

Description

clear clns traffic

Clears all ISO CLNS statistics that are displayed when you use the show clns traffic command.

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

process-tag

(Optional) A unique name among all International Organization for Standardization (ISO) router processes including IP and Connectionless Network Service (CLNS) router processes for a given router. If a process tag is specified, output is limited to the specified routing process. When null is specified for the process tag, output is displayed only for the router process that has no tag specified. If a process tag is not specified, output is displayed for all processes.

level-1

(Optional) Displays the IS-IS link-state database for Level 1. l1 is the abbreviation for the level-1 keyword

level-2

(Optional) Displays the IS-IS link-state database for Level 2. l2 is the abbreviation for the level-2 keyword.

detail

(Optional) Displays the contents of each link-state packet (LSP). Otherwise, a summary display is provided.

lspid

(Optional) Displays the link-state protocol data unit (PDU) identifier. Displays the contents of a single LSP by its ID number.

Command Modes


User EXEC (>)
Privileged EXEC (#)

Command History

Release

Modification

10.0

This command was introduced.

12.2(15)T

Support was added for IPv6.

12.2(18)S

This command was integrated into Cisco IOS Release 12.2(18)S.

12.0(26)S

This command was integrated into Cisco IOS Release 12.0(26)S.

12.0(29)S

The process-tag argument was added.

12.2(28)SB

This command was integrated into Cisco IOS Release 12.2(28)SB.

12.2(25)SG

This command was integrated into Cisco IOS Release 12.2(25)SG.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2(33)SXH

This command was integrated into Cisco IOS Release 12.2(33)SXH.

Cisco IOS XE Release 2.4

This command was introduced on Cisco ASR 1000 Series Routers.

Cisco IOS XE Release 3.3SG

This command was integrated into Cisco IOS XE Release 3.3SG.

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 databasecommand:

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 databasecommand 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

The table below describes the significant fields shown in the display.

Table 4 show isis database Field Descriptions

Field

Description

Tag tagFirst

Tag name that identifies an IS-IS instance.

LSPID

The LSP identifier. The first six octets form the system ID of the router that originated the LSP.

The next octet is the pseudonode ID. When this byte is nonzero, the LSP describes links from the system. When it is zero, the LSP is a so-called nonpseudonode LSP. This mechanism is similar to a router link-state advertisement (LSA) in the Open Shortest Path First (OSPF) protocol. The LSP will describe the state of the originating router.

For each LAN, the designated router for that LAN will create and flood a pseudonode LSP, describing all systems attached to that LAN.

The last octet is the LSP number. If there is more data than can fit in a single LSP, the LSP will be divided into multiple LSP fragments. Each fragment will have a different LSP number. An asterisk (*) indicates that the LSP was originated by the system on which this command is issued.

LSP Seq Num

Sequence number for the LSP that allows other systems to determine if they have received the latest information from the source.

LSP Checksum

Checksum of the entire LSP packet.

LSP Holdtime

Amount of time the LSP remains valid (in seconds). An LSP hold time of zero indicates that this LSP was purged and is being removed from the link-state database (LSDB) of all routers. The value indicates how long the purged LSP will stay in the LSDB before being completely removed.

ATT

The Attach bit. This bit indicates that the router is also a Level 2 router, and it can reach other areas. Level 1-only routers and Level 1-2 routers that have lost connection to other Level 2 routers will use the Attach bit to find the closest Level 2 router. They will point a default route to the closest Level 2 router.

P

The P bit. Detects if the intermediate systems is area partition repair-capable. Cisco and other vendors do not support area partition repair.

OL

The Overload bit. Determines if the IS is congested. If the Overload bit is set, other routers will not use this system as a transit router when calculating routers. Only packets for destinations directly connected to the overloaded router will be sent to this router.

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 databasecommand, the show isis database detail command displays the contents of each LSP.

The table below describes the significant fields shown in the display.

Table 5 show isis database detail Field Descriptions

Field

Description

Area Address

Reachable area addresses from the router. For Level 1 LSPs, these are the area addresses configured manually on the originating router. For Level 2 LSPs, these are all the area addresses for the area to which this router belongs.

Metric

IS-IS metric for the cost of the adjacency between the originating router and the advertised neighbor, or the metric of the cost to get from the advertising router to the advertised destination (which can be an IP address, an end system [ES], or a CLNS prefix).

Topology

States the topology supported (for example, IPv4, IPv6).

IPv6 Address

The IPv6 address.

MT-IPv6

Advertised using multitopology Type, Length, and Value objects (TLVs).

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 details about the Intermediate System-to-Intermediate System (IS-IS) link-state 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

Release

Modification

12.0(5)S

This command was introduced.

12.1(3)T

This command was integrated into Cisco IOS Release 12.1(3)T.

12.0(10)ST

This command was integrated into Cisco IOS Release 12.0(10)ST.

12.2(27)SBC

This command was integrated into Cisco IOS Release 12.2(27)SBC.

12.2(28)SB

This command was integrated into Cisco IOS Release 12.2(28)SB.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2SX

This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.

Cisco IOS XE Release 2.1

This command was implemented on Cisco ASR 1000 Series Aggregation Services Routers.

Cisco IOS XE Release 3.6S

This command was modified. Support was added for administrative tags in IPv6 prefixes.

Examples

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

Device# 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

The table below describes the significant fields shown in the display.

Table 6 show isis database verbose Field Descriptions

Field

Description

LSPID

Link-state packet (LSP) identifier. The first six octets form the System ID of the router that originated the LSP.

The next octet is the pseudonode ID. When this byte is zero, the LSP describes links from the system. When it is nonzero, the LSP is a pseudonode LSP. This is similar to a router LSA in Open Shortest Path First (OSPF); the LSP describes the state of the originating router. For each LAN, the designated router for that LAN creates and floods a pseudonode LSP that describes all systems attached to that LAN.

The last octet is the LSP number. If all the data cannot fit into a single LSP, the LSP is divided into multiple LSP fragments. Each fragment has a different LSP number. An asterisk (*) indicates that the system issuing this command originated the LSP.

LSP Seq Num

LSP sequence number that allows other systems to determine if they received the latest information from the source.

LSP Checksum

Checksum of the entire LSP packet.

LSP Holdtime

Amount of time that the LSP remains valid (in seconds). An LSP hold time of zero indicates that this LSP was purged and is being removed from all routers’ link-state databases (LSDBs). The value indicates how long the purged LSP will stay in the LSDB before it is completely removed.

ATT

Attach bit. This bit indicates that the router is also a Level 2 router, and it can reach other areas. Level 1 routers use the Attach bit to find the closest Level 2 router. They install a default route to the closest Level 2 router.

P

P bit. This bit detects if the IS can repair area partitions. Cisco and other vendors do not support area partition repair.

OL

Overload bit. This bit determines if the IS is congested. If the overload bit is set, other routers do not use this system as a transit router when they calculate routes. Only packets for destinations directly connected to the overloaded router are sent to this router.

Area Address

Reachable area addresses from the router. For Level 1 LSPs, these are the area addresses configured manually on the originating router. For Level 2 LSPs, these are all the area addresses for the area to which this router belongs.

NLPID

Network Layer Protocol identifier.

Hostname

Hostname of the node.

Router ID

Traffic engineering router identifier for the node.

IP Address

IPv4 address for the interface.

Metric

IS-IS metric for the cost of the adjacency between the originating router and the advertised neighbor, or the metric of the cost to get from the advertising router to the advertised destination (which can be an IP address, an end system (ES), or a Connectionless Network Service [CLNS] prefix).

Affinity

Link attribute flags that are being flooded.

Physical BW

Link bandwidth capacity (in bits per second, or b/s).

Reservable BW

Amount of reservable bandwidth on this link, in b/s.

BW Unreserved

Amount of bandwidth that is available for reservation, in b/s.

The following example includes a route tag:

Device# 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

Command

Description

show isis mpls traffic-eng adjacency-log

Displays a log of 20 entries of MPLS traffic engineering IS-IS adjacency changes.

show isis mpls traffic-eng advertisements

Displays the last flooded record from MPLS traffic engineering.

show isis mpls traffic-eng tunnel

Displays information about tunnels considered in the IS-IS next hop calculation.

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 | remote-lfa tunnels }

Syntax Description

interfaces

Displays information about platform support capability for all interfaces running IS-IS.

type

(Optional) Interface type. For more information, use the question mark (?) online help function.

number

(Optional) Interface or subinterface number. For more information about the numbering syntax for your networking device, use the question mark (?) online help function.

summary

Displays FRR configuration information summary.

remote-lfa tunnels

Displays information about remote loop-free alternate (LFA) tunnels.

Command Modes

User EXEC (>)

Privileged EXEC (#)

Command History

Release

Modification

15.1(2)S

This command was introduced.

Cisco IOS XE Release 3.4S

This command was integrated into Cisco IOS XE Release 3.4S.

15.2(2)S

This command was modified. The remote-lfa tunnels keyword was added.

15.2(2)SNI

This command was implemented on the Cisco ASR 901 Series Aggregation Services Routers.

Usage Guidelines

The show isis fast-reroute command displays whether 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

The table below describes the significant fields shown in the display.

Table 7 show isis fast-reroute interfaces Field Descriptions

Field

Description

Protectable

Specifies whether an interface is supported by the platform to be protected by FRR.

Usable for repair

Specifies whether an interface is supported by the platform to be used as a repair path.


Note


Whether an interface is actually FRR protected or is acting as an FRR repair interface depends on the topology and the configuration. The information in the show isis fast-reroute interfaces command shows only the capability of the interface as supported by the platform.


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%

The table below describes the significant fields shown in the display.

Table 8 show isis fast-reroute summary Field Descriptions

Field

Description

Total

Total number of prefixes.

Protected

Total number of protected prefixes.

High priority

Prefixes that have a high priority.

Normal priority

Prefixes that have a normal priority.

The following is sample output from the show isis fast-reroute remote-lfa tunnels command:

Router# show isis fast-reroute remote-lfa tunnels

Tag Null - Fast-Reroute Remote-LFA Tunnels:

  MPLS-Remote-Lfa1: use Et1/0, nexthop 10.0.0.1, end point 24.24.24.24
  MPLS-Remote-Lfa2: use Et0/0, nexthop 10.1.1.2, end point 24.24.24.24

Related Commands

Command

Description

debug isis fast-reroute

Enables debugging of IS-IS FRR.

fast-reroute load-sharing

Disables FRR load sharing of prefixes.

fast-reroute per-prefix

Enables FRR per prefix.

fast-reroute tie-break

Configures the FRR tiebreaking priority.

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

Release

Modification

12.0

This command was introduced.

12.0S

This command was integrated into Cisco IOS Release 12.0(S).

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 dynamiccommand, 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 dynamicly 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

Command

Description

clns host

Defines a name-to-NSAP mapping that can then be used with commands that require NSAPs.

hostname

Specifies or modifies the hostname for the network server.

hostname dynamic

Enables dynamic hostname capability.

net

Configures an IS-IS NET for a CLNS or IS-IS routing process.

show isis ip rib

To display the Intermediate System-to-Intermediate System (IS-IS) IPv4 local routing information base (RIB), use the show isis ip rib command in user EXEC or privileged EXEC mode.

show isis ip rib [ipv4-prefix]

Syntax Description

ipv4-prefix

(Optional) IPv4 address prefix.

Command Modes

User EXEC (>)

Privileged EXEC (#)

Command History

Release

Modification

15.3(3)M

This command was introduced in a release earlier than Cisco IOS Release 15.3(3)M. This command was modified. Filtered routes are now represented with a hyphen (-).

Usage Guidelines

When the optional ipv4-prefix argument is not used, the complete IS-IS IPv4 RIB is displayed. When an optional IPv4 prefix is supplied, only the entry matching that prefix is displayed.

Only the optimal paths will be installed in the master IPv4 RIB as IS-IS routes.

Examples

The following is sample output from the show isis ip rib command. All route paths appear in order of preference, with optimal paths listed first and suboptimal paths listed after optimal paths. A hyphen (-) following any route path indicates routes that are filtered out. In the following example, 2.2.2.2/32 is filtered out.

Device# show isis ip rib

1.1.1.1/32
  [115/L2/20] via 30.30.30.20(Serial3/0), from 2.2.2.2, tag 0, LSP[3/3] 
  [115/L2/20] via 100.100.100.20(Ethernet0/0), from 2.2.2.2, tag 0, LSP[3/3] 

2.2.2.2/32
  [115/L1/20] via 30.30.30.20(Serial3/0), from 2.2.2.2, tag 0, LSP[4/2] -
  [115/L1/20] via 100.100.100.20(Ethernet0/0), from 2.2.2.2, tag 0, LSP[4/2] -
  [115/L2/20] via 30.30.30.20(Serial3/0), from 2.2.2.2, tag 0, LSP[3/3] -
  [115/L2/20] via 100.100.100.20(Ethernet0/0), from 2.2.2.2, tag 0, LSP[3/3] -

20.20.20.0/24
  [115/L1/20] via 30.30.30.20(Serial3/0), from 2.2.2.2, tag 0, LSP[4/2] 
  [115/L1/20] via 100.100.100.20(Ethernet0/0), from 2.2.2.2, tag 0, LSP[4/2] 
  [115/L2/20] via 30.30.30.20(Serial3/0), from 2.2.2.2, tag 0, LSP[3/3] 
  [115/L2/20] via 100.100.100.20(Ethernet0/0), from 2.2.2.2, tag 0, LSP[3/3] 

The table below describes the significant fields shown in the display.

Table 9 show isis ip rib Field Descriptions

Field

Description

1.1.1.1/32

IP prefix that is stored within the IS-IS local RIB.

[115/L2/20]

Administrative distance/type/metric for the routing path to reach the next hop of the router.

Type of path:

  • L1—Level 1
  • L2—Level 2

via 100.100.100.20(Ethernet0/0)

IP address of the next hop—in this instance, Ethernet0/0.

tag

Priority of the IP prefix. All prefixes have a tag 0 priority unless otherwise configured.

LSP[3/3]

Link-state packet (LSP). The numbers following LSP indicate the LSP index and LSP version, respectively.

-

Route paths that are filtered out.

Related Commands

Command

Description

distribute-list in (IP)

Filters routes received in incoming updates.

show isis ipv6 rib

Displays the IS-IS IPv6 local RIB.

redistribute (IP)

Redistributes routes from one routing domain into another routing domain.

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-logcommand in EXEC mode.

show isis lsp-log

Syntax Description

This command has no arguments or keywords.

Command Modes


EXEC

Command History

Release

Modification

12.0

This command was introduced.

12.2(15)T

This command is no longer supported in Cisco IOS Mainline or Technology-based (T) releases. It may continue to appear in Cisco IOS 12.2S-family releases.

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

The table below describes the fields shown in the display.

Table 10 show isis lsp-log Field Descriptions

Field

Description

When

Time elapsed since the LSP was generated.

Count

Number of events that took place at this time.

Interface

Interface that caused the LSP regeneration.

Triggers

Event that triggered the LSP to be flooded. Possible triggers for an LSP are as follows:

  • AREASET--Active area set changed.
  • ATTACHFLAG--Attached bit changed state.
  • CLEAR--Some form of manual clear command was issued.
  • CONFIG--Any configuration change.
  • DELADJ--Adjacency went down.
  • DIS--DIS changed or pseudonode changed.
  • ES--End System adjacency changed.
  • HIPPITY--LSPDB overload bit changed state.
  • IF_DOWN--Needs a new LSP.
  • IP_DEF_ORIG--Default information originate changed.
  • IPDOWN--Directly connected IP prefix down.
  • IP_EXTERNAL--Redistributed IP route appeared or gone.
  • IPIA--Interarea IP route appeared or gone.
  • IPUP--Directly connected IP prefix up.
  • NEWADJ--New adjacency came up.
  • REDIST--Redistributed level-2 CLNS route changed.
  • RRR_INFO--RRR bandwidth resource information.

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

detail

(Optional) Displays more detailed information for IS-IS neighbors.

Command Default

Brief information for IS-IS neighbors is displayed.

Command Modes

Privileged EXEC (#)

Command History

Release

Modification

12.2(18)S

This command was introduced.

12.3

This command was integrated into Cisco IOS Release 12.3.

12.0(29)S

This command was integrated into Cisco IOS Release 12.0(29)S.

12.2(28)SB

This command was integrated into Cisco IOS Release 12.2(28)SB.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2(33)SRB

The command output was modified to support the Multitopology Routing (MTR) feature.

12.2SX

This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.

12.2(33)SRE

This command was integrated into Cisco IOS Release 12.2(33)SRE.

Cisco IOS XE Release 2.5

This command was integrated into Cisco IOS XE Release 2.5.

Usage Guidelines

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

Examples

In Release 12.0(29)S, the show isis neighbors command is entered to display information about the IS-IS neighbor Device1.

Device5# 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              

The show isis neighbors detail command is entered to display more detailed information about the IS-IS neighbor Device1.

Device5# 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

In Release 12.2(33)SRB, the show isis neighbors detail command is entered to verify the status of the IS-IS neighbor Device1 for a network that has MTR configured. For each of the topologies - unicast, DATA and VOICE, the interface information is displayed.

Device5# 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

The table below describes the significant fields shown in the display.

Table 11 show isis neighbors Field Descriptions

Field

Description

System Id

Six-byte value that identifies a system in an area.

Type

Level type. Indicates whether the IS-IS neighbor is a Level 1, Level-1-2, or Level 2 device.

Interface

Interface from which the system was learned.

IP Address

IP address of the neighbor device.

State

Indicates whether the state of the IS-IS neighbor is up or down.

Holdtime

Link-state packet (LSP) holdtime. Amount of time that the LSP remains valid (in seconds).

Circuit Id

Port location for the IS-IS neighbor device that indicates how it is connected to the local device.

Area Address(es)

Reachable area addresses from the device. For Level 1 LSPs, these are the area addresses configured manually on the originating device. For Level 2 LSPs, these are all the area addresses for the area to which this device belongs.

SNPA

Subnetwork point of attachment. This is the data-link address.

State Changed

State change.

LAN Priority

Priority of the LAN.

Remote TID

Neighbor device topology IDs.

Local TID

Local device topology IDs.

show isis nsf

To display current state information regarding Intermediate System-to-Intermediate System (IS-IS) Cisco nonstop forwarding (NSF), use the s how 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

Release

Modification

12.0(22)S

This command was introduced.

12.2(18)S

This command was integrated into Cisco IOS Release 12.2(18)S.

12.2(20)S

Support for the Cisco 7304 router was added.

12.2(28)SB

This command was integrated into Cisco IOS Release 12.2(28)SB.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2(33)SXH

This command was integrated into Cisco IOS Release 12.2(33)SXH.

Usage Guidelines

The show isis nsfcommand 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 table below describes the significant fields shown in the display.

Table 12 show isis nsf Field Descriptions

Field

Description

NSF enabled, mode 'cisco'

NSF is enabled in the default cisco mode.

RP is ACTIVE, standby ready, bulk sync complete

Status of the active RP, standby RP, and the synchronization process between the two.

NSF interval timer expired (NSF restart enabled)

NSF interval timer has expired, allowing NSF restart to be active.

Checkpointing enabled, no errors

Status of the checkpointing process.

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

State of the local RP, the peer RP, and the operating mode these RPs are using.

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

Command

Description

debug isis nsf

Displays information about the IS-IS state during an NSF restart.

nsf (IS-IS)

Configures NSF operations for IS-IS.

nsf t3

Specifies the methodology used to determine how long IETF NSF will wait for the LSP database to synchronize before generating overloaded link state information for itself and flooding that information out to its neighbors.

nsf interface wait

Specifies how long a NSF restart will wait for all interfaces with IS-IS adjacencies to come up before completing the restart.

nsf interval

Specifies the minimum time between NSF restart attempts.

show clns neighbors

Displays both ES and IS neighbors.

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

ip-address

(Optional) Displays paths for a specific route.

ip-address-mask

(Optional) Displays paths for all routes under a major network.

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

Release

Modification

12.0(26)S

This command was introduced.

12.3(4)T

This command was integrated into Cisco IOS Release 12.3(4)T.

12.2(25)S

This command was integrated into Cisco IOS Release 12.2(25)S

12.2(18)SXE

This command was integrated into Cisco IOS Release 12.2(18)SXE.

12.2(27)SBC

This command was integrated into Cisco IOS Release 12.2(27)SBC.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

15.1(2)S

This command was integrated into Cisco IOS Release 15.1(2)S.

15.2(2)SNI

This command was implemented on the Cisco ASR 901 Series Aggregation Services Routers.

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 ribcommand 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]

The table below describes the significant fields shown in the display.

Table 13 show isis rib Field Descriptions

Field

Description

10.2.2.0/24

IP prefix that is stored within the IS-IS local RIB.

[115/L2/20]

Administrative instance/type/metric for the routing path to reach the next hop of the router.

via 10.2.2.2(Ethernet2)

IP address of the next hop--in this instance, Ethernet2.

tag 0

Priority of the IP prefix. All prefixes have a tag 0 priority unless otherwise configured.

Related Commands

Command

Description

debug isis rib

Displays debug information for IP Version 4 routes within the global or IS-IS local RIB.

ip route priority high

Assigns a high priority to an IS-IS IP prefix.

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

level-1

(Optional) Displays level 1 local redistribution cache information.

level-2

(Optional) Displays level 2 local redistribution cache information.

network-prefix

(Optional) The network ID in the A.B.C.D format for a specific network.

Command Modes


User EXEC (>)
Privileged EXEC (#)

Command History

Release

Modification

12.0(27)S

This command was introduced.

12.3(7)T

This command was integrated into Cisco IOS Release 12.3(7)T.

12.2(25)S

This command was integrated into Cisco IOS Release 12.2(25)S.

12.2(18)SXE

This command was integrated into Cisco IOS Release 12.2(18)SXE.

12.2(27)SBC

This command was integrated into Cisco IOS Release 12.2(27)SBC.

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 shows 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 ======

Field

Description

10.3.3.0/24 [Connected/0] external

Indicates 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.

10.0.18.48/28 [Connected/0] external

Indicates that the prefix 10.0.18.48 with a mask 28 was redistributed from the connected routing protocol into IS-IS as a level 1 route, cost 0, with a metric type external.

Related Commands

Command

Description

clear isis rib redistribution

Clears some or all prefixes in the local redistribution cache.

debug isis rib redistribution

Debugs the local redistribution cache event.

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 command in privileged EXEC mode.

show isis [area-tag] [ ipv6 | * ] spf-log [ topology { ipv6 | topology-name | * } ]

Syntax Description

area-tag

(Optional) Required for multiarea Intermediate System-to-Intermediate System (IS-IS) configuration. Optional for conventional IS-IS configuration.

Meaningful name for a routing process. This name must be unique among all IP or Connectionless Network Service (CLNS) router processes for a given router. If an area tag is not specified, a null tag is assumed and the process is referenced with a null tag. If an area tag is specified, output is limited to the specified area.

ipv6

(Optional) Displays the IS-IS multitopology for IPv6 SPF log.

*

(Optional) Displays the SPF logs of all address families.

topology

(Optional) Specifies the Multiple Transport Stream Receiver (MTR) topology.

topology-name

(Optional) The IS-IS multitopology SPF log for the specified topology name.

Command Modes


Privileged EXEC (#)

Command History

Release

Modification

10.0

This command was introduced.

12.2(15)T

Support was added for IPv6.

12.2(18)S

This command was integrated into Cisco IOS Release 12.2(18)S.

12.0(26)S

This command was integrated into Cisco IOS Release 12.0(26)S.

12.2(28)SB

This command was integrated into Cisco IOS Release 12.2(28)SB.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2(33)SXH

This command was integrated into Cisco IOS Release 12.2(33)SXH.

Cisco IOS XE Release 2.4

This command was introduced on Cisco ASR 1000 Series Aggregation Services Routers.

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

The table below describes the significant fields shown in the display.

Table 14 show isis spf-log Field Descriptions

Field

Description

When

How long ago (in hours: minutes: seconds) a full SPF calculation occurred. The last 20 occurrences are logged.

Duration

Number of milliseconds required to complete this SPF run. Elapsed time is wall clock time, not CPU time.

Nodes

Number of routers and pseudonodes (LANs) that make up the topology calculated in this SPF run.

Count

Number of events that triggered this SPF run. When there is a topology change, often multiple link-state packets (LSPs) are received in a short time. A router waits 5 seconds before running a full SPF run, so it can include all new information. This count denotes the number of events (such as receiving new LSPs) that occurred while the router was waiting its 5 seconds before running full SPF.

Last trigger LSP

Whenever a full SPF calculation is triggered by the arrival of a new LSP, the router stores the LSP ID. The LSP ID can provide a clue as to the source of routing instability in an area. If multiple LSPs are causing an SPF run, only the LSP ID of the last received LSP is remembered.

Triggers

A list of all reasons that triggered a full SPF calculation. For a list of possible triggers, see the table below.

The table below lists possible triggers of a full SPF calculation.

Table 15 Possible Triggers of Full SPF Calculation

Trigger

Description

ADMINDIST

Another administrative distance was configured for the IS-IS process on this router.

AREASET

Set of learned area addresses in this area changed.

ATTACHFLAG

This router is now attached to the Level 2 backbone or it has just lost contact to the Level 2 backbone.

BACKUPOVFL

An IP prefix disappeared. The router knows there is another way to reach that prefix but has not stored that backup route. The only way to find the alternative route is through a full SPF run.

DBCHANGED

A clear isis * command was issued on this router.

IPBACKUP

An IP route disappeared, which was not learned via IS-IS, but via another protocol with better administrative distance. IS-IS will run a full SPF to install an IS-IS route for the disappeared IP prefix.

IPQUERY

A clear ip route command was issued on this router.

LSPEXPIRED

Some LSP in the link-state database (LSDB) has expired.

LSPHEADER

ATT/P/OL bits or is-type in an LSP header changed.

NEWADJ

This router has created a new adjacency to another router.

NEWAREA

A new area (via network entity title [NET]) was configured on this router.

NEWLEVEL

A new level (via is-type) was configured on this router.

NEWLSP

A new router or pseudonode appeared in the topology.

NEWMETRIC

A new metric was configured on an interface of this router.

NEWSYSID

A new system ID (via NET) was configured on this router.

PERIODIC

Typically, every 15 minutes a router runs a periodic full SPF calculation.

RTCLEARED

A clear clns route command was issued on this router.

TLVCODE

TLV code mismatch, indicating that different type length values (TLVs) are included in the newest version of an LSP.

TLVCONTENT

TLV contents changed. This normally indicates that an adjacency somewhere in the area has come up or gone down. The “Last trigger LSP” column indicates where the instability may have occurred.

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 [hostname] [ level-1 | level-2 | l1 | l2 ]

Syntax Description

process-tag

(Optional) A unique name among all International Organization for Standardization (ISO) router processes including IP and Connectionless Network Service (CLNS) router processes for a given router. If a process tag is specified, output is limited to the specified routing process. When null is specified for the process tag, output is displayed only for the router process that has no tag specified. If a process tag is not specified, output is displayed for all processes.

ipv6

(Optional) Displays Intermediate System-to-Intermediate System (IS-IS) IPv6 topology.

*

(Optional) Displays the topology of all address families.

hostname

(Optional) Hostname or the Network Service Access Point (NSAP) address of the router.

level-1

(Optional) Specifies paths to all level one routers in the area.

level-2

(Optional) Specifies paths to all level two routers in the domain.

l1

(Optional) Abbreviation for the level-1 keyword.

l2

(Optional) Abbreviation for the level-2 keyword.

Command Modes


Privileged EXEC (#)


Command History

0S Release

Modification

12.0(26)S

This command was integrated into Cisco IOS Release 12.0(26)S.

12.0(29)S

This command was modified. The process-tag argument was added.

S Release

Modification

12.2(18)S

This command was integrated into Cisco IOS Release 12.2(18)S.

SB Release

Modification

12.2(28)SB

This command was integrated into Cisco IOS Release 12.2(28)SB.

SG Release

Modification

12.2(25)SG

This command was integrated into Cisco IOS Release 12.2(25)SG.

SX Release

Modification

12.2(33)SXH

This command was integrated into Cisco IOS Release 12.2(33)SXH.

Mainline and T Release

Modification

12.0(5)T

This command was introduced.

12.2(15)T

This command was modified. Support was added for IPv6.

XE Release

Modification

Cisco IOS XE Release 2.4

This command was introduced on Cisco ASR 1000 Series Routers.

Cisco IOS XE Release 3.3SG

This command was integrated into Cisco IOS XE Release 3.3SG.

Usage Guidelines

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

If you are running Cisco IOS Release 12.2(33)SRB or a later release, use the show isis topology(MTR) command.

Examples

The following is sample 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 

The table below describes the significant fields shown in the display.

Table 16 show isis topology Field Descriptions

Field

Description

Tag

Identifies the routing process.

System Id

Six-byte value that identifies a system in an area.

Metric

IS-IS metric for the cost of the adjacency between the originating router and the advertised neighbor, or the metric of the cost to get from the advertising router to the advertised destination (which can be an IP address, an end system [ES], or a CLNS prefix).

Next-Hop

The address of the next hop router.

Interface

Interface from which the system was learned.

SNPA

Subnetwork point of attachment. This is the data-link address.

Related Commands

Command

Description

show clns es-neighbors

Lists the ES neighbors that this router knows.

show clns is-neighbors

Displays IS-IS related information for IS-IS router adjacencies.

show clns neighbors

Displays the ES, IS, and M-ISIS neighbors.

show clns neighbor areas

Displays information about IS-IS neighbors and the areas to which they belong.

show clns route

Displays one or all of the destinations to which the router knows how to route CLNS packets.

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 isiscommand in global configuration mode. To disable all or some of the IS-IS SNMP notifications, use the noform of this command.

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

no snmp-server enable traps isis [ errors [error-type] ] [ state-change [state-change-type] ]

Syntax Description

errors

(Optional) Enables Simple Network Management Protocol (SNMP) notifications for errors and mismatches that occur as a result of invalid field values in PDUs that have been received on a circuit for an IS.

error-type

(Optional) One or more of the optional IS-IS error type keywords can follow the errors keyword:

  • authentication --Enables SNMP notifications only for authentication failures in a PDU received by an IS.
  • authentication-type --Enables SNMP notifications only for invalid authentication type fields in a PDU received by an IS.
  • id-length-mismatch --Enables SNMP notifications only for mismatches in system ID field lengths.
  • iih --Enables SNMP notifications only for IS-IS Hello PDU errors. One or more of the following three optional IS-IS Hello PDU error keywords can follow the iih keyword:
    • adjacency-rejected--Enables SNMP notifications for link-state packet (LSP)-specific errors and mismatches.
    • area-mismatch--Enables SNMP notifications for mismatches in area addresses between ISs.
    • version-skew--Enables SNMP notifications for IS-IS protocol version mismatches.
  • lsp --Enables SNMP notifications only for LSP-specific errors and mismatches. One or more of the following eight optional IS-IS Hello PDU error keywords can follow the lsp keyword:
    • buffsize-mismatch--Enables SNMP notifications for buffer size mismatches for LSPs.
    • max-seq-overflow--Enables SNMP notifications for attempts to exceed the maximum sequence number.
    • packet-corrupt--Enables SNMP notifications for LSP in-memory corruptions with invalid checksums.
    • packet-parse--Enables SNMP notifications for packet parse failures on received circuit.
    • protocol-support--Enables SNMP notifications for supported protocol mismatches non-pseudonode LSPs.
    • purge-zero-age--Enables SNMP notifications for invalid attempts to purge the LSP of an IS.
    • size-exceeded--Enables SNMP notifications for oversized LSPs that cause propagation failures.
    • skip-sequence-number--Enables SNMP notifications for system ID duplications (the sequence number is greater than 1).
  • manual-address-drop --Enables SNMP notifications only for manually configured area addresses that have been dropped.
  • maxarea-mismatch --Enables SNMP notifications only for mismatches in maximum area address values.

state-change

(Optional) Enables SNMP notifications for all IS-IS transition state change traps.

state-change-type

(Optional) One or both of the optional IS-IS transition state change keywords can follow the state-change keyword:

  • adjacency --Enables SNMP notifications only for adjacency changes between IS-IS neighbors.
  • database-overload --Enables SNMP notifications only for authentication failures on IS-IS neighbors.

Command Default

This command is disabled by default. If you enter this command with no keywords, the default is to enable all SNMP notifications.

Command Modes


Global configuration

Command History

Release

Modification

12.2(25)SG

This command was introduced.

12.2(31)SB2

This command was integrated into Cisco IOS Release 12.2(31)SB2.

12.2(33)SRB

This command was integrated into Cisco IOS Release 12.2(33)SRB.

12.2(31)SB3

This command was implemented on the Cisco 10000 series.

Usage Guidelines

To globally enable all IS-IS MIB traps, enter the snmp-server enable traps isiscommand in global configuration mode. If you want to disable one or more traps, you can enter the no snmp-server enable traps isis errorscommand or the no snmp-server enable traps isis state-changecommand followed by the keywords that represent the traps that you want to disable. Entering the no snmp-server enable traps isis errorscommand without any keywords will disable all IS-IS error traps. Entering the no snmp-server enable traps isis state-changecommand without any keywords will disable all IS-IS state-change traps.

Examples

The following example shows how to enable the router to send IS-IS SNMP notifications only for IS-IS errors involving authentication to the host at the address myhost.cisco.com using the community string defined as public:

Router(config)# snmp-server enable traps isis errors authentication
Router(config)# snmp-server host myhost.cisco.com version 2c public

The following example shows how to enable the router to send IS-IS SNMP notifications for state changes involving adjacencies between Intermediate Systems (ISs) to the host at the address myhost.cisco.com using the community string defined as public:

Router(config)# snmp-server enable traps isis state-change adjacency
Router(config)# snmp-server host myhost.cisco.com version 2c public

Related Commands

Command

Description

snmp-server host

Spec ifies the r ecipient of an SNMP notification operation.

spf-interval

To customize Intermediate System-to-Intermediate System (IS-IS) throttling of shortest path first (SPF) calculations, use the spf-interval command in router configuration mode. To restore default values, use the no form of this command.

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

no spf-interval

Syntax Description

level-1

(Optional) Apply intervals to Level-1 areas only.

level-2

(Optional) Apply intervals to Level-2 areas only.

spf-max-wait

Indicates the maximum interval (in seconds) between two consecutive SPF calculations. The range is 1 to 120 seconds. The default is 10 seconds.

spf-initial-wait

(Optional) Indicates the initial SPF calculation delay (in milliseconds) after a topology change. The range is 1 to 120000 milliseconds. The default is 5500 milliseconds (5.5 seconds).

spf-second-wait

(Optional) Indicates the hold time between the first and second SPF calculation (in milliseconds). The range is 1 to 120000 milliseconds. The default is 5500 milliseconds (5.5 seconds).

Command Default

spf-max-wait : 10 secondsspf-initial-wait: 5500 millisecondsspf-second-wait: 5500 milliseconds

Command Modes


Router configuration (config-router)

Command History

Release

Modification

10.3

This command was introduced.

12.1

The level-1 and level-2 keywords were added; the spf-max-wait, spf-initial-wait, and spf-second-wait arguments were added. The default interval between SPF calculations was changed from 5 seconds to 10 seconds.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2SX

This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.

15.1(2)S

This command was integrated into Cisco IOS Release 15.1(2)S.

Usage Guidelines

SPF calculations are performed only when the topology changes. They are not performed when external routes change.

The spf-intervalcommand controls how often Cisco IOS software performs the SPF calculation. The SPF calculation is processor-intensive. Therefore, it may be useful to limit how often this is done, especially when the area is large and the topology changes often. Increasing the SPF interval reduces the processor load of the router, but potentially slows down the rate of convergence.

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

  • The spf-initial-wait argument indicates the initial wait time (in milliseconds) after a topology change before the first SPF calculation.
  • The spf-second-wait argument indicates the interval (in milliseconds) between the first and second SPF calculation.
  • Each subsequent wait interval is twice as long as the previous one until the wait interval reaches the spf-max-wait interval specified; the SPF calculations are throttled or slowed down after the initial and second intervals. Once the spf-max-wait 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 spf-max-wait interval, fast behavior is restored (the initial wait time).

SPF throttling is not a dampening mechanism; that is, SPF throttling does not prevent SPF calculations or mark any route, interface, or router as down. SPF throttling simply increases the intervals between SPF calculations.

Examples

The following example configures intervals for SPF calculations, partial route calculation (PRC), and link-state packet (LSP) generation:

router isis
 spf-interval 5 10 20
 prc-interval 5 10 20
 lsp-gen-interval 2 50 100

srlg

To assign an interface to a Shared Risk Link Group (SRLG) and to configure interface-specific SRLG, use the srlg command in interface configuration mode. To disable the configuration, use the no form of this command.

srlg gid srlg-id

no srlg gid srlg-id

Syntax Description

gid

Specifies the SRLG group ID.

srlg-id

SRLG ID. Valid values are from 1 to 8192.

Command Default

No interfaces are assigned to an SRLG.

Command Modes


Interface configuration (config-if)

Command History

Release

Modification

15.1(2)S

This command was introduced.

Usage Guidelines

The SRLG configuration assigns an interface to one or more risk groups. When an interface assigned to one group fails, the other interfaces that are part of the group also fail.

Examples

The following example shows how to assign an SRLG group ID to a Gigabit Ethernet interface:

Router(config)# interface gigabitethernet 0/0
Router(config-if)# srlg gid 900
Router(config-if)# end

Related Commands

Command

Description

interface

Configures an interface and enters interface configuration mode.

summary-address (IS-IS)

To create aggregate addresses for Intermediate System-to-Intermediate System (IS-IS), use the summary-address command in router configuration mode. To restore the default, use the no form of this command.

summary-address address mask [ level-1 | level-1-2 | level-2 ] [ tag tag-number ] [ metric metric-value ]

no summary-address address mask [ level-1 | level-1-2 | level-2 ] [ tag tag-number ] [ metric metric-value ]

Syntax Description

address

Summary address designated for a range of addresses.

mask

IP subnet mask used for the summary route.

level-1

(Optional) Only routes redistributed into Level 1 are summarized with the configured address and mask value.

level-1-2

(Optional) Summary routes are applied when redistributing routes into Level 1 and Level 2 IS-IS, and when Level 2 IS-IS advertises Level 1 routes as reachable in its area.

level-2

(Optional) Routes learned by Level 1 routing are summarized into the Level 2 backbone with the configured address and mask value. Redistributed routes into Level 2 IS-IS will be summarized also.

tag tag-number

(Optional) Specifies the integer used to tag the summary route.

metric metric-value

(Optional) Specifies the metric value applied to the summary route.

Command Default

All routes are advertised individually.

Command Modes


Router configuration (config-router)

Command History

Release

Modification

10.0

This command was introduced.

12.3(2)T

The following keywords and arguments were added:

  • tag tag-number
  • metric metric-value

12.2(27)SBC

This command was integrated into Cisco IOS Release 12.2(27)SBC.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2SX

This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.

Cisco IOS XE Release 2.1

This command was implemented on Cisco ASR 1000 Series Aggregation Services Routers.

Usage Guidelines

M ultiple groups of addresses can be summarized for a given level. Routes learned from other routing protocols can also be summarized. The metric used to advertise the summary is the smallest metric of all the more specific routes. This command helps reduce the size of the routing table.

This command also reduces the size of the link-state packets (LSPs) and thus the link-state database (LSDB). It also helps network stability because a summary advertisement is depending on many more specific routes. A single route flap does not cause the summary advertisement to flap in most cases.

The drawback of summary addresses is that other routes might have less information to calculate the most optimal routing table for all individual destinations.

Examples

The following example redistributes Routing Information Protocol (RIP) routes into IS-IS. In a RIP network, there are IP routes for 10.1.1, 10.1.2, 10.1.3, 10.1.4, and so on. This example advertises only 10.1.0.0 into the IS-IS Level 1 link-state protocol data unit (PDU). The summary address is tagged with 100 and given a metric value of 110.

router isis
 net 01.0000.0000.0001.00
 redistribute rip level-1 metric 40
 summary-address 10.1.0.0 255.255.0.0 tag 100 metric 110

vrf (router configuration)

To associate an Intermediate System-to-Intermediate System (IS-IS) instance with a VPN routing and forwarding instance (VRF), use the vrf command in router configuration mode. To remove the VRF, use the no form of this command.

vrf vrf-name

no vrf vrf-name

Syntax Description

vrf-name

Name of the VRF to which you want to associate an IS-IS instance.

Command Default

An ISIS instance is not associated with a VRF.

Command Modes


Router configuration (config-router)

Command History

Release

Modification

12.0(29)S

This command was introduced.

12.2(33)SRB

This command was integrated into Cisco IOS Release 12.2(33)SRB.

15.0(1)M

This command was integrated into Cisco IOS Release 15.0(1)M.

Cisco IOS XE Release 3.3SG

This command was integrated into Cisco IOS XE Release 3.3SG.

Usage Guidelines

You must already have created the VRF before you can associate it with an IS-IS instance. The following restrictions should be noted:

  • IS-IS instances running Connectionless Network Services (CLNS) must have the same system ID.
  • An IS-IS instance that is running CLNS or IPv6 cannot be associated with a VRF.
  • You can configure only one IS-IS instance to run both CLNS and IP.
  • IS-IS instances within the same VRF must have unique system IDs, although IS-IS instances located in separate VRFs can have the same system ID.
  • You can associate an IS-IS instance with only one VRF.
  • You can configure the passive-interface default command only on one IS-IS instance per VRF.
  • Redistribution is allowed only within the same VRF.
  • You can enable only one IS-IS instance per interface.
  • An interface can belong to an IS-IS instance only if they are associated with the same VRF.

For more information about configuring VRF-aware IS-IS instances, see the IS-IS Support for Multiple Instances (IP only) Each Mapped to a VRF feature.

Examples

The following example shows the creation of an IS-IS instance that gets associated with a VRF called First:

Router(config)# router isis tagFirst
Router(config-router)# vrf First

Related Commands

Command

Description

ip router isis

Configures an IS-IS process for IP on an interface and attaches a tag designator to the routing process.

router isis

Enables the IS-IS routing protocol and specifies an IS-IS process.

show clns neighbors

Displays ES, IS, and M-ISIS neighbors.

show clns protocol

Lists the protocol-specific information for each ISO IGRP or IS-IS routing process in the router.

show isis database

Displays the IS-IS link-state database.