Table Of Contents

lsp-full suppress

lsp-gen-interval (IPX)

lsp-gen-interval (IS-IS)

lsp-refresh-interval (IS-IS)

max-area-addresses

metric

metric-style wide

net

partition avoidance

prc-interval

protocol shutdown

redistribute isis

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 hostname

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

summary-address (IS-IS)

vrf (router configuration)

lsp-full suppress

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

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

no lsp-full suppress

Syntax Description

external	Suppresses any redistributed routes on this router.
interlevel	(Optional) Suppresses any routes coming from the other level. For example, if the Level-2 LSP becomes full, routes from Level 1 are suppressed.
none	(Optional) Suppresses no routes.

Defaults

If this command is not specified, or if this command is specified with no keyword, the default value used is external.

Command Modes

Router configuration

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.

Usage Guidelines

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

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

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

Examples

This example specifies that if the LSP becomes full, both redistributed routes and routes from another level will be suppressed from the LSP:

router isis

 lsp-full suppress interlevel

Related Commands

Command	Description
clear isis lsp-full	Clears the LSPFULL state.
redistribute maximum-prefix	Limits the number of prefixes redistributed into IS-IS or generates a warning when the number of prefixes redistributed into IS-IS reaches a maximum.

lsp-gen-interval (IPX)

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

lsp-gen-interval seconds

no lsp-gen-interval seconds

Syntax Description

seconds

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

Defaults

5 seconds

Command Modes

Router configuration

Command History

Release	Modification
10.3	This command was introduced.
12.2(33)SRA	This command was integrated into Cisco IOS Release 12.2(33)SRA.
12.2SX	This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.

Usage Guidelines

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

Examples

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

lsp-gen-interval 10

Related Commands

Command	Description
ipx router	Specifies the routing protocol to use.
spf-interval	Controls how often Cisco IOS software performs the SPF calculation.

lsp-gen-interval (IS-IS)

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

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

no lsp-gen-interval

Syntax Description

level-1	(Optional) Apply intervals to Level-1 areas only.
level-2	(Optional) Apply intervals to Level-2 areas only.
lsp-max-wait	Indicates the maximum interval (in seconds) between two consecutive occurrences of an LSP being generated. The range is 1 to 120 seconds. The default is 5 seconds.
lsp-initial-wait	(Optional) Indicates the initial LSP generation delay (in milliseconds). The range is 1 to 120,000 milliseconds. The default is 50 milliseconds.
lsp-second-wait	(Optional) Indicates the hold time between the first and second LSP generation (in milliseconds). The range is 1 to 120,000 milliseconds. The default is 5000 milliseconds (5 seconds).

Defaults

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

Command Modes

Router configuration

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.

Usage Guidelines

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

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

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

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

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

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

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

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

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

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

Examples

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

router isis

 spf-interval 5 10 20

 prc-interval 5 10 20

 lsp-gen-interval 2 50 100

Related Commands

Command	Description
isis lsp-interval	Sets the time delay between successive IS-IS LSP transmissions.
isis retransmit-interval	Sets the amount of time between retransmission of each IS-IS LSP on a point-to-point link.
isis retransmit-throttle-interval	Sets the minimum delay between retransmissions on each LSP on a point-to-point interface.

lsp-refresh-interval (IS-IS)

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

lsp-refresh-interval seconds

no lsp-refresh-interval

Syntax Description

seconds

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

Defaults

900 seconds (15 minutes)

Command Modes

Router configuration

Command History

Release	Modification
10.3	This command was introduced.
12.2(33)SRA	This command was integrated into Cisco IOS Release 12.2(33)SRA.
12.2SX	This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.

Usage Guidelines

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

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

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

Examples

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

router isis 

 lsp-refresh-interval 1080

Related Commands

Command	Description
max-lsp-lifetime (IS-IS)	Sets the maximum time that link-state packets (LSPs) can remain in a router's database without being refreshed.

max-area-addresses

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

max-area-addresses number

no max-area-addresses number

Syntax Description

number

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

Command Default

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

Command Modes

Router configuration

Command History

Release	Modification
10.0	This command was introduced.
12.2(33)SRA	This command was integrated into Cisco IOS Release 12.2(33)SRA.
12.2SX	This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.

Usage Guidelines

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

Examples

The following example configures three manual addresses as follows:

router isis

 max-area-addresses 3

 net 50.3131.3131.3131.00

 net 51.3131.3131.3131.00

 net 52.3131.3131.3131.00

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

router isis

 max-area-addresses 2

 net 50.3131.3131.3131.00 

 net 51.3131.3131.3131.00 

 net 52.3131.3131.3131.00 

%The maximum allowed addresses already configured

Related Commands

Command	Description
net	Assigns a NET address to an IS-IS router.

metric

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

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

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

Syntax Description

default-value	Metric value to be assigned to the link and used to calculate the path cost via the links to destinations. You can configure this metric for Level 1 or Level 2 routing only. For style wide metrics the range is from 1 to 16777214. For style narrow metrics the range is from 1 to 63.
level-1	(Optional) Set IS-IS Level-1 IPv4 or IPv6 metric.
level-2	(Optional) Set IS-IS Level-2 IPv4 or IPv6 metric.

Defaults

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

Command Modes

Interface configuration
Address family configuration

Command History

Release	Modification
12.3(4)T	This command was introduced.
12.0(27)S	This command was integrated into Cisco IOS Release 12.0(27)S.
12.2(25)S	This command was integrated into Cisco IOS Release 12.2(25)S.
12.2(18)SXE	This command was integrated into Cisco IOS Release 12.2(18)SXE.
12.2(27)SBC	This command was integrated into Cisco IOS Release 12.2(27)SBC.
12.2(33)SRA	This command was integrated into Cisco IOS Release 12.2(33)SRA.

Usage Guidelines

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

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

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

---

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

---

Examples

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

interface Ethernet3/1

 ip address 10.10.10.2 255.255.0.0

 ip router isis area1

 no ip route-cache

 duplex half

!

interface Ethernet3/2

 ip address 10.10.10.130 255.255.255.0

 ip router isis area1

 no ip route-cache

 duplex half

!

router isis area1

 net 01.0000.0309.1234.00

 metric-style wide

 metric 111

Entering the show clns interface command returns the following information:

Router# show clns interface

Ethernet3/1 is up, line protocol is up

  Checksums enabled, MTU 1497, Encapsulation SAP

  ERPDUs enabled, min. interval 10 msec.

  CLNS fast switching enabled

  CLNS SSE switching disabled

  DEC compatibility mode OFF for this interface

  Next ESH/ISH in 39 seconds

  Routing Protocol: IS-IS

    Circuit Type: level-1-2

    Interface number 0x0, local circuit ID 0x1

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

    Level-1 IPv6 Metric: 10

    Number of active level-1 adjacencies: 0

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

    Level-2 IPv6 Metric: 10

    Number of active level-2 adjacencies: 0

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

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

Ethernet3/2 is up, line protocol is up

  Checksums enabled, MTU 1497, Encapsulation SAP

  ERPDUs enabled, min. interval 10 msec.

  CLNS fast switching enabled

  CLNS SSE switching disabled

  DEC compatibility mode OFF for this interface

  Next ESH/ISH in 20 seconds

  Routing Protocol: IS-IS

    Circuit Type: level-1-2

    Interface number 0x1, local circuit ID 0x2

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

    Level-1 IPv6 Metric: 10

    Number of active level-1 adjacencies: 1

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

    Level-2 IPv6 Metric: 10

    Number of active level-2 adjacencies: 1

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

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

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

interface Ethernet3/1

 ip address 10.10.10.2 255.255.0.0

 ip router isis area1

 no ip route-cache

 duplex half

 isis metric 10

!

interface Ethernet3/2

 ip address 10.10.10.10 255.255.255.0

 ip router isis area1

 no ip route-cache

 duplex half

router isis area1

 net 01.0000.0309.1234.00

 metric-style wide

 metric 111

 !

 address-family ipv6

 metric 222

 exit-address-family

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

Router# show clns interface

Ethernet3/1 is up, line protocol is up

  Checksums enabled, MTU 1497, Encapsulation SAP

  ERPDUs enabled, min. interval 10 msec.

  CLNS fast switching enabled

  CLNS SSE switching disabled

  DEC compatibility mode OFF for this interface

  Next ESH/ISH in 51 seconds

  Routing Protocol: IS-IS

    Circuit Type: level-1-2

    Interface number 0x0, local circuit ID 0x1

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

    Level-1 IPv6 Metric: 222

    Number of active level-1 adjacencies: 0

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

    Level-2 IPv6 Metric: 222

    Number of active level-2 adjacencies: 0

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

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

Ethernet3/2 is up, line protocol is up

  Checksums enabled, MTU 1497, Encapsulation SAP

  ERPDUs enabled, min. interval 10 msec.

  CLNS fast switching enabled

  CLNS SSE switching disabled

  DEC compatibility mode OFF for this interface

  Next ESH/ISH in 17 seconds

  Routing Protocol: IS-IS

    Circuit Type: level-1-2

    Interface number 0x1, local circuit ID 0x2

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

    Level-1 IPv6 Metric: 222

    Number of active level-1 adjacencies: 1

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

    Level-2 IPv6 Metric: 222

    Number of active level-2 adjacencies: 1

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

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

Related Commands

Command	Description
isis ipv6 metric	Configures the value of an IS-IS IPv6 metric.
isis metric	Configures the metric for an interface.

metric-style wide

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

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

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

Syntax Description

transition	(Optional) Instructs the router to accept both old- and new-style TLVs.
level-1	(Optional) Enables this command on routing level 1.
level-2	(Optional) Enables this command on routing level 2.
level-1-2	(Optional) Enables this command on routing levels 1 and 2.

Defaults

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

Command Modes

Router configuration

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 of this train depends on your feature set, platform, and platform hardware.

Usage Guidelines

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

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

---

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

---

Examples

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

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

Related Commands

Command	Description
metric-style narrow	Configures a router to generate and accept old-style TLVs.
metric-style transition	Configures a router to generate and accept both old-style and new-style TLVs.

net

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

net net1 alt net2

no net net

Syntax Description

net1	NET network services access point (NSAP) name or address for the IS-IS routing process on the Mulltilayer Switch Feature Card (MSFC) in the primary slot; see the "Usage Guidelines" section for additional information about valid values.
alt net2	Specifies the NET name or address for the IS-IS routing process on the MSFC in the alternate slot; see the "Usage Guidelines" section for additional information about valid values.
net	NET NSAP name or address to be removed.

Defaults

The defaults are as follows:

•No NET is configured.

•The IS-IS process is disabled.

Command Modes

Global configuration

Command History

Release	Modification
10.0	This command was introduced.
12.2(14)SX	Support for this command was introduced on the Supervisor Engine 720.
12.2(17d)SXB	Support for this command on the Supervisor Engine 2 was extended to Release 12.2(17d)SXB.
12.2(33)SRA	This command was integrated into Cisco IOS Release 12.2(33)SRA.

Usage Guidelines

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

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

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

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

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

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

•A network configuration has multiple areas that are merged.

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

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

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

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

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

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

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

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

Examples

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

router isis firstcompany

 net 47.0004.004d.0001.0001.0c11.1111.00

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

clns routing

.

.

.

interface Tunnel529

 ip address 10.0.0.5 255.255.255.0

 ip router isis BB

 clns router isis BB

interface Ethernet1

 ip address 10.1.1.5 255.255.255.0

 ip router isis A3253-01

 clns router isis A3253-01

!

interface Ethernet2

 ip address 10.2.2.5 255.255.255.0

 ip router isis A3253-02

 clns router isis A3253-02

.

.

.

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

 net 49.2222.0000.0000.0005.00

!

router isis A3253-01

 net 49.0553.0001.0000.0000.0005.00

 is-type level-1

!

router isis A3253-02

 net 49.0553.0002.0000.0000.0005.00

 is-type level-1

Related Commands

Command	Description
is-type	Configures the routing level for an instance of the IS-IS routing process.
router isis	Enables the IS-IS routing protocol and specifies an IS-IS process.
show isis topology	Displays a list of all connected routers in all areas.

partition avoidance

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

partition avoidance area-tag

no partition avoidance area-tag

Syntax Description

area-tag

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

Defaults

This command is disabled by default.

Command Modes

Router configuration

Command History

Release	Modification
12.0(5)T	This command was introduced.
12.2(33)SRA	This command was integrated into Cisco IOS Release 12.2(33)SRA.
12.2SX	This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.

Usage Guidelines

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

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

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

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

Examples

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

router isis Finance

 partition avoidance area1

Related Commands

Command	Description
is-type	Configures the routing level for an instance of the IS-IS routing process.
router isis	Enables the IS-IS routing protocol and specifies an IS-IS process.

prc-interval

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

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

no prc-interval

Syntax Description

prc-max-wait	Indicates the maximum interval (in seconds) between two consecutive PRC calculations. Value range is 1 to 120 seconds. The default is 5 seconds.
prc-initial-wait	(Optional) Indicates the initial PRC calculation delay (in milliseconds) after a topology change. The range is 1 to 120,000 milliseconds. The default is 2000 milliseconds.
prc-second-wait	(Optional) Indicates the hold time between the first and second PRC calculation (in milliseconds). The range is 1 to 120,000 milliseconds. The default is 5000 milliseconds (5 seconds).

Defaults

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

Command Modes

Router configuration

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.

Usage Guidelines

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

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

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

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

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

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

Examples

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

router isis

 spf-interval 5 10 20

 prc-interval 5 10 20

 lsp-gen-interval 2 50 100

protocol shutdown

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

protocol shutdown

no protocol shutdown

Syntax Description

This command has no arguments or keywords.

Defaults

No default behavior or values

Command Modes

Router configuration

Command History

Release	Modification
12.3(4)T	This command was introduced.
12.0(27)S	This command was integrated into Cisco IOS Release 12.0(27)S.
12.2(25)S	This command was integrated into Cisco IOS Release 12.2(25)S.
12.2(18)SXE	This command was integrated into Cisco IOS Release 12.2(18)SXE.
12.2(27)SBC	This command was integrated into Cisco IOS Release 12.2(27)SBC.

Usage Guidelines

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

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

Examples

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

Router(config)# router isis area1

Router(config-router)# protocol shutdown

Related Commands

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

redistribute isis

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

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

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

Syntax Description

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.

Defaults

There are no default values for this command.

Command Modes

Router configuration

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.

Usage Guidelines

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

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

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

Examples

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

router isis

 net 49.0000.0000.0001.00

 metric-style wide

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

access-list 100 permit ip 10.10.10.0 0.0.0.255 any

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

router isis

 net 49.0000.0000.0001.00

 metric-style wide

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

route-map match-tag permit 10

 match tag 110

Related Commands

Command	Description
metric-style wide	Configures a router running IS-IS so that it generates and accepts only new-style TLVs.

router isis

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

router isis area-tag

no router isis area-tag

Syntax Description

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 (CLNS) router processes for a given router. Required for multiarea IS-IS configuration. Optional for conventional IS-IS configuration.

Defaults

This command is disabled by default.

Command Modes

Global configuration

Command History

Release	Modification
10.0	This command was introduced.
12.0(5)T	Multiarea functionality was added, changing the way the tag argument (now area-tag) 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.

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 software 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 configures IS-IS for IP routing, with system ID 0000.0000.0002 and area ID 01.0001, and enables IS-IS to form adjacencies on Ethernet interface 0 and serial interface 0. The IP prefix assigned to Ethernet interface 0 will be advertised to other IS-IS routers.

router isis tag1

 net 01.0001.0000.0000.0002

 is-type level-1

!

interface ethernet 0

 ip address 10.1.1.1 255.255.255.0

 ip router isis

!

interface serial 0

 ip unnumbered ethernet0

 ip router isis

The following example starts IS-IS routing with the optional area-tag argument, where CISCO is the value for the area-tag argument:

router isis CISCO