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Integrated IS-IS Commands: L through V
- log-adjacency-changes (IS-IS)
- lsp-full suppress
- lsp-gen-interval (IPX)
- lsp-gen-interval (IS-IS)
- lsp-refresh-interval (IS-IS)
- max-area-addresses
- metric
- metric-style wide
- microloop avoidance
- microloop avoidance rib-update-delay
- net
- partition avoidance
- prc-interval
- protocol shutdown
- redistribute isis
- redistribute isis (IPv6)
- router isis
- set-attached-bit
- set-overload-bit
- show clns interface
- show clns is-neighbors
- show clns traffic
- show isis database
- show isis database verbose
- show isis fast-reroute
- show isis hostname
- show isis ip rib
- show isis lsp-log
- show isis neighbors
- show isis nsf
- show isis rib
- show isis rib redistribution
- show isis spf-log
- show isis topology
- snmp-server enable traps isis
- spf-interval
- srlg
- summary-address (IS-IS)
- vrf (router configuration)
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.
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.
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.
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.
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.
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.
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 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 100Related 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.
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).
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.
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 52.3131.3131.3131.00In 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 configuredmetric
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.
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 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.
NoteThe 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 111Entering 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 secondsThe 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-familyEnter 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 millisecondsmetric-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 ]
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 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.
NoteThis 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.
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.
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 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)# endmicroloop 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.
Syntax Description
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.
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.
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.0001.0001.0c11.1111.00The 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 49.0553.0002.0000.0000.0005.00partition 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.
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 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.
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.
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 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).
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.
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.
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 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 anyIn 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 110Related 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 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 100Related 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.
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 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 isisThe 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 exampleThe 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 FinanceThe following example shows usage of the maximum-paths option:
router isis maximum-paths? 20Related 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.
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.
NoteWildcarded 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 58set-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 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 100show clns interface
To list the CLNS-specific information about each interface, use the show clns interface command in privileged EXEC mode.
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 secondsExamples
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 enabledThe 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.
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.
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 VThe 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: 0:03:35Notice 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.
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.
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.
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: 0The 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.
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.
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 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 0/0/0The 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 0/0/0The 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.03As 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 172.16.65.0 255.255.255.0show 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.
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-5The 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: 50Related 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.
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 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: NoThe 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.
NoteWhether 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 24.24.24.24show 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.
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)# endEntering 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-aRelated 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.
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.
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.
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 IPIAThe table below describes the fields shown in the display.
show isis neighbors
To display information about Intermediate System-to-Intermediate System (IS-IS) neighbors, use the show isis neighbors command in privileged EXEC mode.
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 R5.02The 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 VIn 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, 200The 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.
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:SSOThe 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:SSOThe 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:FALSERelated 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.
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 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.
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.
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.
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.
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 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 TLVCONTENTThe 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.
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 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.ccdeThe 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
Command Default
This command is disabled by default. If you enter this command with no keywords, the default is to enable all SNMP notifications.
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 publicThe 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 publicspf-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 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.
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.
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.
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 History
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 110vrf (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.
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 FirstRelated 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.
