Table Of Contents
default-information originate (IS-IS)
isis retransmit-throttle-interval
Integrated IS-IS Commands
Use the commands in this chapter to configure and monitor Intermediate System-to-Intermediate System (IS-IS) protocol. For IS-IS configuration information and examples, refer to the "Configuring Integrated IS-IS" chapter of the Cisco IOS IP and IP Routing Configuration Guide.
area-password
To configure the Intermediate System-to-Intermediate System (IS-IS) area authentication password, use the area-password command in router configuration mode. To disable the password, use the no form of this command.
area-password password
no area-password [password]
Syntax Description
Defaults
No area password is defined and area password authentication is disabled.
Command Modes
Router configuration
Command History
Usage Guidelines
Using the area-password command on all routers in an area will prevent unauthorized routers from injecting false routing information into the linkstate database.
This password is exchanged as plain text and thus this feature provides only limited security.
This password is inserted in Level 1 (station router level) link state PDUs (LSPs), complete sequence number PDUs (CSNPs), and partial sequence number PDUs (PSNP).
Examples
The following example assigns an area authentication password:
router isisarea-password angelRelated Commands
Configures the IS-IS routing domain authentication password.
Configures the authentication password for an interface.
default-information originate (IS-IS)
To generate a default route into an Intermediate System-to-Intermediate System (IS-IS) routing domain, use the default-information originate command in router configuration mode. To disable this feature, use the no form of this command.
default-information originate [route-map map-name]
no default-information originate [route-map map-name]
Syntax Description
route-map map-name
(Optional) Routing process will generate the default route if the route map is satisfied.
Defaults
This command is disabled by default.
Command Modes
Router configuration
Command History
Usage Guidelines
If a router configured with this command has a route to 0.0.0.0 in the routing table, IS-IS will originate an advertisement for 0.0.0.0 in its link-state packets (LSPs).
Without a route-map, the default is only advertised in L2 LSPs. For L1 routing, there is another mechanism to find the default route, which is to look for the closest L1L2 router. The closest L1L2 router can be found by looking at the attached-bit (ATT) in L1 LSPs.
A route-map can be used for two things: 1) make the router generate default in its L1 LSPs.
2) advertise 0/0 conditionally. With a match ip address standard-access-list command, you can specify one or more IP routes that must exist before the router will advertise 0/0.Examples
The following example forces the software to generate a default external route into an IS-IS domain:
router isis! BGP routes will be distributed into IS-ISredistribute bgp 120! access list 2 is applied to outgoing routing updatesdistribute-list 2 outdefault-information originate! access list 2 defined as giving access to network 10.105.0.0access-list 2 permit 10.105.0.0 0.0.255.255Related Commands
redistribute
Redistributes routes from one routing domain into another routing domain.
Displays the IS-IS link state database.
domain-password
To configure the Intermediate System-to-Intermediate System (IS-IS) routing domain authentication password, use the domain-password command in router configuration mode. To disable a password, use the no form of this command.
domain-password password
no domain-password [password]
Syntax Description
Defaults
No password is specified and no authentication is enabled for exchange of L2 routing information.
Command Modes
Router configuration
Command History
Usage Guidelines
This password is exchanged as plain text and thus this feature provides only limited security.
This password is inserted in Level 2 (area router level) link state PDUs (LSPs), complete sequence number PDUs (CSNPs), and partial sequence number PDUs (PSNPs).
Examples
The following example assigns an authentication password to the routing domain:
router isisdomain-password flowerRelated Commands
Configures the IS-IS area authentication password.
Configures the authentication password for an interface.
hello padding
To reenable IS-IS hello padding at the router level, enter the hello padding command in router configuration mode. To disable IS-IS hello padding, use the no form of this command.
hello padding
no hello padding
Syntax Description
This command has no arguments or keywords.
Defaults
IS-IS hello padding is enabled.
Command Modes
Router configuration
Command History
12.0(5)T
This command was introduced.
12.0(5)S
This command was integrated into Cisco IOS Release 12.0(5)S.
Usage Guidelines
Intermediate System-to-Intermediate System (IS-IS) hellos are padded to the full maximum transmission unit (MTU) size. The benefit of padding IS-IS hellos to the full MTU is that it allows for early detection of errors that result from transmission problems with large frames or errors that result from mismatched MTUs on adjacent interfaces.
You can disable hello padding in order to avoid wasting network bandwidth in case the MTU of both interfaces is the same or, in case of translational bridging. While hello padding is disabled, Cisco routers still send the first five IS-IS hellos padded to the full MTU size, in order to maintain the benefits of discovering MTU mismatches.
To disable hello padding for all interfaces on a router for the IS-IS routing process, enter the no hello padding command in router configuration mode. To selectively disable hello padding for a specific interface, enter the no isis hello padding command in interface configuration mode.
Examples
In the following example the no hello padding command is used to turn off hello padding at the router level:
Router(config)# router isisRouter(config-router)# no hello paddingRouter(config-router)# endThe show clns interfaces command is entered to show that hello padding has been turned off at router level:
Router# show clns interface e0/0Ethernet0/0 is up, line protocol is upChecksums enabled, MTU 1497, Encapsulation SAPERPDUs enabled, min. interval 10 msec.CLNS fast switching enabledCLNS SSE switching disabledDEC compatibility mode OFF for this interfaceNext ESH/ISH in 4 secondsRouting Protocol: IS-ISCircuit Type: level-1-2Interface number 0x0, local circuit ID 0x1Level-1 Metric: 10, Priority: 64, Circuit ID: Router_B.01Level-1 IPv6 Metric: 10Number of active level-1 adjacencies: 1Level-2 Metric: 10, Priority: 64, Circuit ID: Router_B.01Level-2 IPv6 Metric: 10Number of active level-2 adjacencies: 1Next IS-IS LAN Level-1 Hello in 6 seconds! No hello paddingNext IS-IS LAN Level-2 Hello in 2 seconds! No hello paddingWhen the debug isis adj packets command is entered, the output will show the IS-IS hello protocol data unit (PDU) length when a hello packet has been sent to or received from an IS-IS adjacency. In the following example the IS-IS hello PDU length is 1497:
Router# debug isis adj packets e0/0IS-IS Adjacency related packets debugging is onRouter_A#*Oct 11 18:04:17.455: ISIS-Adj: Sending L1 LAN IIH on Ethernet0/0, length 55*Oct 11 18:04:19.075: ISIS-Adj: Rec L2 IIH from aabb.cc00.6600 (Ethernet0/0), cir type L1L2, cir id 0000.0000.000B.01, length 1497Related Commands
ip router isis
To configure an Intermediate System-to-Intermediate System (IS-IS) routing process for IP on an interface and to attach an area designator to the routing process, use the ip router isis command in interface configuration mode. Use the no form of the command to disable IS-IS for IP.
ip router isis area-tag
no ip router isis area-tag
Syntax Description
Defaults
No routing processes are specified.
Command Modes
Interface configuration
Command History
10.0
This command introduced.
12.0(5)T
Multiarea functionality was added, changing the way the tag argument (now area-tag) is used.
Usage Guidelines
Before the IS-IS routing process is useful, a network entity title (NET) must be assigned with the net command and some interfaces must have IS-IS enabled.
If you have IS-IS running and at least one ISO-Interior Gateway Routing Protocol (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 process to perform Level 2 (interarea) routing. If Level 2 routing is configured on any process, all additional processes are automatically configured as Level 1. You can configure this process to perform intra-area (Level 1) routing at the same time. You can configure up to 29 additional processes as Level 1-only processes. Use the is-type command to remove Level 2 routing from a router instance. You can then use the is-type command to enable Level 2 routing on some other IS-IS router instance.
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, for example) where subinterfaces are supported, different subinterfaces could be configured for different areas.
Examples
The following example specifies IS-IS as an IP routing protocol for a process named Finance, and specifies that the Finance process will be routed on interfaces Ethernet 0 and serial 0:
router isis Financenet 49.0001.aaaa.aaaa.aaaa.00interface Ethernet 0ip router isis Financeinterface serial 0ip router isis FinanceThe following example shows an IS-IS configuration with two Level 1 areas and one Level 1-2 area:
ip routing...interface Tunnel529ip address 10.0.0.5 255.255.255.0ip router isis BBinterface Ethernet1ip address 10.1.1.5 255.255.255.0ip router isis A3253-011!interface Ethernet2ip address 10.2.2.5 255.255.255.0ip router isis A3253-02...! Defaults to "is-type level-1-2"router isis BBnet 49.2222.0000.0000.0005.00!router isis A3253-01net 49.0553.0001.0000.0000.0005.00is-type level-1!router isis A3253-02net 49.0553.0002.0000.0000.0005.00is-type level-1Related Commands
Configures an IS-IS network entity title (NET) for the routing process.
Enables the IS-IS routing protocol.
isis circuit-type
To configure the type of adjacency, use the isis circuit-type command in interface configuration mode. To reset the circuit type to Level l and Level 2, use the no form of this command.
isis circuit-type {level-1 | level-1-2 | level-2-only}
no isis circuit-type
Syntax Description
Defaults
A Level 1 and Level 2 adjacency is established.
Command Modes
Interface configuration
Command History
Usage Guidelines
Normally, this command does not need to be configured. The proper way is to configure a router as an Level 1-only, Level 1-2 or Level 2-only system. Only on routers that are between areas (Level 1-2 routers) should you configure some interfaces to be Level 2-only to prevent wasting bandwidth by sending out unused Level 1 hellos. Note that on point-to-point interfaces, the Level 1 and Level 2 hellos are in the same packet.
Examples
In the following example, other routers on Ethernet interface 0 are in the same area. Other routers on Ethernet interface 1 are in other areas, so the router will stop sending Level 1 hellos.
interface ethernet 0ip router isisinterface ethernet 1isis circuit-type level-2-onlyisis csnp-interval
To configure the Intermediate System-to-Intermediate System (IS-IS) complete sequence number PDUs (CSNP) interval, use the isis csnp-interval command in interface configuration mode. To restore the default value, use the no form of this command.
isis csnp-interval seconds {level-1 | level-2}
no isis csnp-interval {level-1 | level-2}
Syntax Description
Defaults
10 seconds
Level 1 and Level 2Command Modes
Interface configuration
Command History
Usage Guidelines
It is very unlikely you will need to change the default value of this command.
This command applies only for the designated router (DR) for a specified interface. Only DRs send CSNP packets in order to maintain database synchronization. The CSNP interval can be configured independently for Level 1 and Level 2. This feature does not apply to serial point-to-point interfaces. It does apply to WAN connections if the WAN is viewed as a multiaccess meshed network.
For multi-access WAN interfaces (such as ATM, Frame Relay, and X.25), it is highly recommended you configure the NBMA cloud as multiple point-to-point subinterfaces. Doing so will make routing much more robust if one or more PVCs fail.
The isis csnp-interval command on point-to-point subinterfaces only makes sense when using it in combination with the IS-IS mesh-group feature.
Examples
The following example configures Ethernet interface 0 for sending CSN PDUs every 30 seconds.
interface ethernet 0isis csnp-interval 30 level-1isis display delimiter
To make output from multiarea displays easier to read by specifying the delimiter to use to separate displays of information, use the isis display delimiter command in global configuration mode. This command displays the output from different areas as a string or additional white space. Use the no form of the command to disable this output format. cnt
isis display delimiter [return cnt | char cnt]
no isis display delimiter [return cnt | char cnt]
Syntax Description
return
(Optional) Delimit with carriage returns.
cnt
(Optional) Number of carriage returns or length of string to use for delimiter.
char
(Optional) Character to use for delimiter string.
Defaults
By default the isis display delimiter command is disabled.
Command Modes
Global configuration
Command History
Usage Guidelines
Use this command to customize display output when the IS-IS multiarea feature is used.
Examples
The following command causes different areas in multiarea displays (such as show command output) to be delimited by a string of dashes (-):
isis display delimiter - 14With three IS-IS neighbors configured, this command displays the following output from the show clns neighbors command:
Router# show clns neighbors--------------Area L2BB:System Id Interface SNPA State Holdtime Type Protocol0000.0000.0009 Tu529 172.21.39.9 Up 25 L1L2 IS-IS--------------Area A3253-01:System Id Interface SNPA State Holdtime Type Protocol0000.0000.0053 Et1 0060.3e58.ccdb Up 22 L1 IS-IS0000.0000.0003 Et1 0000.0c03.6944 Up 20 L1 IS-IS--------------Area A3253-02:System Id Interface SNPA State Holdtime Type Protocol0000.0000.0002 Et2 0000.0c03.6bc5 Up 27 L1 IS-IS0000.0000.0053 Et2 0060.3e58.ccde Up 24 L1 IS-ISRelated Commands
isis hello padding
To reenable IS-IS hello padding at the interface level, enter the isis hello padding command in interface configuration mode. To disable IS-IS hello padding, use the no form of this command.
isis hello padding
no isis hello padding
Syntax Description
This command has no arguments or keywords.
Defaults
IS-IS hello padding is enabled.
Command Modes
Interface configuration
Command History
12.0(5)T
This command was introduced.
12.0(5)S
This command was integrated into Cisco IOS Release 12.0(5)S.
Usage Guidelines
Intermediate System-to-Intermediate System (IS-IS) hellos are padded to the full maximum transmission unit (MTU) size. The benefit of padding IS-IS hellos to the full MTU is that it allows for early detection of errors that result from transmission problems with large frames or errors that result from mismatched MTUs on adjacent interfaces.
You can disable hello padding in order to avoid wasting network bandwidth in case the MTU of both interfaces is the same or, in case of translational bridging. While hello padding is disabled, Cisco routers still send the first five IS-IS hellos padded to the full MTU size, in order to maintain the benefits of discovering MTU mismatches.
To selectively disable hello padding for a specific interface, enter the no isis hello padding command in interface configuration mode. To disable hello padding for all interfaces on a router for the IS-IS routing process, enter the no hello padding command in router configuration mode.
Examples
To turn off hello padding at the interface level for the Ethernet interface 0/0, enter the no isis hello padding command in interface configuration mode:
Router# configure terminalEnter configuration commands, one per line. End with CNTL/Z.Router(config)# interface e0/0Router(config-if)# no isis hello paddingRouter(config-if)# endWhen the show clns neighbor command is entered for Ethernet interface 0/0, the output confirms that hello padding has been turned off for both Level 1 and Level 2 circuit types:
Router_A# show clns interface e0/0Ethernet0/0 is up, line protocol is upChecksums enabled, MTU 1497, Encapsulation SAPERPDUs enabled, min. interval 10 msec.CLNS fast switching enabledCLNS SSE switching disabledDEC compatibility mode OFF for this interfaceNext ESH/ISH in 47 secondsRouting Protocol: IS-ISCircuit Type: level-1-2Interface number 0x0, local circuit ID 0x1Level-1 Metric: 10, Priority: 64, Circuit ID: Router_B.01Level-1 IPv6 Metric: 10Number of active level-1 adjacencies: 1Level-2 Metric: 10, Priority: 64, Circuit ID: Router_B.01Level-2 IPv6 Metric: 10Number of active level-2 adjacencies: 1Next IS-IS LAN Level-1 Hello in 2 seconds! No hello paddingNext IS-IS LAN Level-2 Hello in 2 seconds! No hello paddingWhen the debug isis adj packets command is entered, the output will show the IS-IS hello protocol data unit (PDU) length when a hello packet has been sent to or received from an IS-IS adjacency. In the following example the IS-IS hello PDU length is 1497:
Router# debug isis adj packets e0/0IS-IS Adjacency related packets debugging is onRouter#*Oct 11 18:04:17.455: ISIS-Adj: Sending L1 LAN IIH on Ethernet0/0, length 55*Oct 11 18:04:19.075: ISIS-Adj: Rec L2 IIH from aabb.cc00.6600 (Ethernet0/0), cir type L1L2, cir id 0000.0000.000B.01, length 1497Related Commands
isis hello-interval
To specify the length of time between hello packets that the Cisco IOS software sends, use the isis hello-interval command in interface configuration mode. To restore the default value, use the no form of this command.
isis hello-interval {seconds | minimal} [level-1 | level-2]
no isis hello-interval {level-1 | level-2}
Syntax Description
seconds
An integer value. By default, a value three times the hello interval seconds is advertised as the holdtime in the hello packets sent. (That multiplier of 3 can be changed by specifying the isis hello-multiplier command.) With smaller hello intervals, topological changes are detected faster, but there is more routing traffic. The default is 10 seconds.
minimal
Causes the system to compute the hello interval based on the hello multiplier (specified by the isis hello-multiplier command) so that the resulting hold time is 1 second.
level-1
Configures the hello interval for Level 1 independently. Use this on X.25, Switched Multimegabit Data Service (SMDS), and Frame Relay multiaccess networks.
level-2
Configures the hello interval for Level 2 independently. Use this on X.25, SMDS, and Frame Relay multiaccess networks.
Defaults
10 seconds
Level 1 and Level 2Command Modes
Interface configuration
Command History
Usage Guidelines
The hello interval multiplied by the hello multiplier equals the hold time. If the minimal keyword is specified, the hold time is 1 second and the system computes the hello interval based on the hello multiplier.
The hello interval can be configured independently for Level 1 and Level 2, except on serial point-to-point interfaces. (Because there is only a single type of hello packet sent on serial links, it is independent of Level 1 or Level 2.) The level-1 and level-2 keywords are used on X.25, SMDS, and Frame Relay multiaccess networks or LAN interfaces.
A faster hello interval gives faster convergence, but increases bandwidth and CPU usage. It might also add to instability in the network. A slower hello interval saves bandwidth and CPU. Especially when used in combination with a higher hello multiplier, this may increase overall network stability.
It makes more sense to tune the hello interval and hello multiplier on point-to-point interfaces than on LAN interfaces.
Examples
The following example configures serial interface 0 to advertise hello packets every 5 seconds. The router is configured to act as a station router. This will cause more traffic than configuring a longer interval, but topological changes will be detected faster.
interface serial 0isis hello-interval 5 level-1Related Commands
Specifies the number of IS-IS hello packets a neighbor must miss before the router should declare the adjacency as down.
isis hello-multiplier
To specify the number of Intermediate System-to-Intermediate System (IS-IS) hello packets a neighbor must miss before the router should declare the adjacency as down, use the isis hello-multiplier command in interface configuration mode. To restore the default value, use the no form of this command.
isis hello-multiplier multiplier {level-1 | level-2}
no isis hello-multiplier {level-1 | level-2}
Syntax Description
Defaults
multiplier: 3
Level 1 and Level 2Command Modes
Interface configuration
Command History
Usage Guidelines
The "holding time" carried in an IS-IS hello packet determines how long a neighbor waits for another hello packet before declaring the neighbor to be down. This time determines how quickly a failed link or neighbor is detected so that routes can be recalculated.
Use the isis hello-multiplier command in circumstances where hello packets are lost frequently and IS-IS adjacencies are failing unnecessarily. You can raise the hello multiplier and lower the hello interval (isis hello-interval command) correspondingly to make the hello protocol more reliable without increasing the time required to detect a link failure.
On point-to-point links, there is only one hello for both Level 1 and Level 2, so configuring different hello-multipliers only makes sense for multi-access networks, such as Ethernet, FDDI, etc. Separate Level 1 and Level 2 hellos are also sent over NBMA networks in multipoint mode, such as X.25, Frame Relay and ATM. However, it is recommended to run IS-IS over point-to-point subinterfaces over WAN NBMA media.
Examples
In the following example, the network administrator wants to increase network stability by making sure an adjacency will go down only when many (10) hellos are missed. The total time to detect link failure is 60 seconds. This will ensure that the network remains stable, even when the link is fully congested.
interface serial 1ip router isisisis hello-interval 6 level-1isis hello-multiplier 10 level-1Related Commands
Specifies the length of time between hello packets that the Cisco IOS software sends.
isis lsp-interval
To configure the time delay between successive Intermediate System-to-Intermediate System (IS-IS) link state packet transmissions, use the isis lsp-interval command in interface configuration mode. To restore the default value, use the no form of this command.
isis lsp-interval milliseconds
no isis lsp-interval
Syntax Description
Defaults
The default time delay is 33 milliseconds.
Command Modes
Interface configuration
Command History
Usage Guidelines
In topologies with a large number of IS-IS neighbors and interfaces, a router may have difficulty with the CPU load imposed by link state packet (LSP) transmission and reception. This command allows the LSP transmission rate (and by implication the reception rate of other systems) to be reduced.
Examples
The following example causes the system to send LSPs every 100 milliseconds (10 packets per second) on serial interface 0:
interface serial 0isis lsp-interval 100Related Commands
Configures the time between retransmission of each LSP (IS-IS link state PDU) over point-to-point links.
isis mesh-group
To optimize link-state packet (LSP) flooding in nonbroadcast multiaccess (NBMA) networks with highly meshed, point-to-point topologies, use the isis mesh-group command in interface configuration mode. To remove a (sub)interface from a mesh group, use the no form of this command.
isis mesh-group [num | blocked]
no isis mesh-group [num | blocked]
Syntax Description
num
(Optional) A number identifying the mesh group of which this interface is a member.
blocked
(Optional) Specifies that no LSP flooding will take place on this (sub)interface.
Defaults
The interface performs normal flooding.
Command Modes
Interface configuration
Command History
Usage Guidelines
LSPs that are first received on (sub)interfaces that are not part of a mesh group are flooded to all other (sub)interfaces in the usual way.
LSPs that are first received on (sub)interfaces that are part of a mesh group are flooded to all interfaces except those in the same mesh-group. If the "blocked" keyword is configured on a (sub)interface, then a newly received LSP is not flooded out over that interface.
To minimize the possibility of incomplete flooding, you should allow unrestricted flooding over at least a minimal set of links in the mesh. Selecting the smallest set of logical links that covers all physical paths results in very low flooding, but less robustness. Ideally you should select only enough links to ensure that LSP flooding is not detrimental to scaling performance, but enough links to ensure that under most failure scenarios no router will be logically disconnected from the rest of the network. In other words, blocking flooding on all links permits the best scaling performance, but there is no flooding. Permitting flooding on all links results in very poor scaling performance.
Examples
In the following example six interfaces are configured in three mesh groups. LSPs received are handled as follows:
•
LSPs received first via atm 1/0.1 are flooded to all interfaces except atm 1/0.2 (which is part of the same mesh group) and atm 1/2.1, which is blocked.
•
•
interface atm 1/0.1 ip router isis isis mesh-group 10interface atm 1/0.2ip router isis isis mesh-group 10interface atm 1/1.1 ip router isis isis mesh-group 11interface atm 1/1.2 ip router isis isis mesh-group 11interface atm 1/2.1 ip router isisisis mesh-group blockedinterface atm 1/2.2 ip router isisRelated Commands
isis metric
To configure the metric for an interface, use the isis metric command in interface configuration mode. To restore the default metric value, use the no form of this command.
isis metric default-metric {level-1 | level-2}
no isis metric {level-1 | level-2}
Syntax Description
Defaults
If level-1 or level-2 is not specified, level-1-2 is assumed.
Command Modes
Interface configuration
Command History
Usage Guidelines
Specifying the level-1 or level-2 keywords resets the metric only for Level 1 or Level 2 routing, respectively.
It is highly recommended to configure metrics on all interfaces. If you do not do so, the IS-IS metrics are similar to hop-count metrics.
Examples
The following example configures serial interface 0 for a default link-state metric cost of 15 for Level 1:
interface serial 0isis metric 15 level-1isis password
To configure the authentication password for an interface, use the isis password command in interface configuration mode. To disable authentication for Intermediate System-to-Intermediate System (IS-IS), use the no form of this command.
isis password password {level-1 | level-2}
no isis password {level-1 | level-2}
Syntax Description
Defaults
This command is disabled by default.
If no keyword is specified, the default is level-1-2.Command Modes
Interface configuration
Command History
Usage Guidelines
This command enables you to prevent unauthorized routers from forming adjacencies with this router, and thus protects the network from intruders.
The password is exchanged as plain text and thus provides only limited security.
Different passwords can be assigned for different routing levels using the level-1 and level-2 kewords.
Specifying the level-1 or level-2 keywords disables the password only for Level 1 or Level 2 routing, respectively.
Examples
The following example configures a password for Ethernet interface 0 at Level 1:
interface ethernet 0isis password frank level-1isis priority
To configure the priority of designated routers, use the isis priority command in interface configuration mode. To reset the default priority, use the no form of this command.
isis priority value {level-1 | level-2}
no isis priority {level-1 | level-2}
Syntax Description
value
Sets the priority of a router and is a number from 0 to 127. The default value is 64.
level-1
Sets the priority for Level 1 independently.
level-2
Sets the priority for Level 2 independently.
Defaults
Priority of 64
Level 1 and Level 2Command Modes
Interface configuration
Command History
Usage Guidelines
Priorities can be configured for Level 1 and Level 2 independently. Specifying the level-1 or level-2 keywords resets priority only for Level 1 or Level 2 routing, respectively.
The priority is used to determine which router on a LAN will be the designated router or Designated Intermediate System (DIS). The priorities are advertised in the hellos. The router with the highest priority will become the DIS.
In IS-IS, there is no backup designated router. Setting the priority to 0 lowers the chance of this system becoming the DIS, but does not prevent it. If a router with a higher priority comes on line, it will take over the role from the current DIS. In the case of equal priorities, the highest MAC address breaks the tie.
Examples
The following example shows Level 1 routing given priority by setting the priority level to 80. This router is now more likely to become the DIS.
interface ethernet 0isis priority 80 level-1isis retransmit-interval
To configure the amount of time between retransmission of each Intermediate System-to-Intermediate System (IS-IS) link-state packet (LSP) on a point-to-point link, use the isis retransmit-interval command in interface configuration mode. To restore the default value, use the no form of this command.
isis retransmit-interval seconds
no isis retransmit-interval seconds
Syntax Description
Defaults
5 seconds
Command Modes
Interface configuration
Command History
Usage Guidelines
The setting of the seconds argument should be conservative, or needless retransmission will result.
This command has no effect on LAN (multipoint) interfaces. On point-to-point links, the value can be increased to enhance network stability.
Retransmissions occur only when LSPs are dropped. So setting this to a higher value has little effect on reconvergence. The more neighbors routers have, and the more paths over which LSPs can be flooded, the higher this value can be made.
The value should be larger for serial lines.
Examples
The following example configures serial interface 0 for retransmission of IS-IS LSP, every 60 seconds for a large serial line:
interface serial 0isis retransmit-interval 60Related Commands
isis retransmit-throttle-interval
To configure the amount of time between retransmissions on each Intermediate System-to-Intermediate System (IS-IS) link-state packet (LSP) on a point-to-point interface, use the isis retransmit-throttle-interval command in interface configuration mode. To restore the default value, use the no form of this command.
isis retransmit-throttle-interval milliseconds
no isis retransmit-throttle-interval
Syntax Description
Defaults
The delay is determined by the isis lsp-interval command.
Command Modes
Interface configuration
Command History
Usage Guidelines
This command may be useful in very large networks with many LSPs and many interfaces as a way of controlling LSP retransmission traffic. This command controls the rate at which LSPs can be re-sent on the interface.
The isis retransmit-throttle-interval command is distinct from the rate at which LSPs are sent on the interface (controlled by the isis lsp-interval command) and the period between retransmissions of a single LSP (controlled by the isis retransmit-interval command). These commands may all be used in combination to control the offered load of routing traffic from one router to its neighbors.
Examples
The following example configures serial interface 0 to limit the rate of LSP retransmissions to one every 300 milliseconds:
interface serial 0isis retransmit-throttle-interval 300Related Commands
is-type
To configure the routing level for an instance of the Intermediate System-to-Intermediate System (IS-IS) routing process, use the is-type command in router configuration mode. To reset the default value, use the no form of this command.
is-type {level-1 | level-1-2 | level-2-only}
no is-type {level-1 | level-1-2 | level-2-only}
Syntax Description
Defaults
In conventional IS-IS configurations, the router acts as both a Level 1 (intra-area) and a Level 2 (interarea) router.
In multiarea IS-IS configurations, the first instance of the IS-IS routing process configured is by default a Level 1-2 (intra-area and interarea) router. The remaining instances of the IS-IS process configured by default are Level 1 routers.
Command Modes
Router configuration
Command History
10.3
This command was introduced.
12.0(5)T
This command was modified to include multiarea IS-IS routing.
Usage Guidelines
It is highly recommended that you configure the type of an IS-IS routing process. If you are configuring multiarea IS-IS, you must configure the type of the router, or allow it to be configured by default. By default, the first instance of the IS-IS routing process that you configure using the router isis command is a Level 1-2 router.
If there is only one area in the network, there is no need to run both Level 1 and Level 2 routing algorithms. If IS-IS is used for Connectionless Network Service (CLNS) routing (and there is only one area), Level 1-only must be used everywhere. If IS-IS is used for IP routing only (and there is only one area), you can run Level 2-only everywhere. Areas you add after the Level 1-2 area exists are by default Level 1 areas.
If the router instance has been configured for Level 1-2 (the default for the first instance of the IS-IS routing process in a Cisco unit), you can remove Level 2 (interarea) routing for the area using the is-type command. You can also use the is-type command to configure Level 2 routing for an area, but it must be the only instance of the IS-IS routing process configured for Level 2 on the Cisco unit.
Examples
The following example specifies an area router:
router isisis-type level-2-onlyRelated Commands
Enables the IS-IS routing protocol and specifies an IS-IS process.
show clns neighbor areas
Displays information about IS-IS neighbors and the areas to which they belong.
lsp-gen-interval
To customize IS-IS throttling of link-state PDU (LSP) generation, use the lsp-gen-interval command in router configuration mode. To restore default values, use the no form of this command.
lsp-gen-interval [level-1 | level-2] lsp-max-wait [lsp-initial-wait lsp-second-wait]
no lsp-gen-interval
Syntax Description
Defaults
lsp-max-wait: 5 seconds
lsp-initial-wait: 50 milliseconds
lsp-second-wait: 5000 millisecondsCommand Modes
Router configuration
Command History
Usage Guidelines
The following description will help you determine whether to change the default values of this command:
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Notice that the lsp-gen-interval command controls the delay between LSPs being generated, as opposed to the following related commands:
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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 isisspf-interval 5 10 20prc-interval 5 10 20lsp-gen-interval 2 50 100Related Commands
lsp-refresh-interval (IS-IS)
To set the link-state packet (LSP) refresh interval, use the lsp-refresh-interval command in router configuration mode. To restore the default refresh interval, use the no form of this command.
lsp-refresh-interval seconds
no lsp-refresh-interval
Syntax Description
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
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 isislsp-refresh-interval 1080Related Commands
Sets the maximum time that link-state packets (LSPs) can remain in a router's database without being refreshed.
max-lsp-lifetime (IS-IS)
To set the maximum time that link-state packets (LSPs) can remain in a router's database without being refreshed, use the max-lsp-lifetime command in router configuration mode. To restore the default lifetime, use the no form of this command.
max-lsp-lifetime seconds
no max-lsp-lifetime
Syntax Description
seconds
Lifetime of the LSP in seconds. The range is 1 to 65535 seconds; the default is 1200 seconds (20 minutes).
Defaults
1200 seconds (20 minutes)
Command Modes
Router configuration
Command History
Usage Guidelines
If the lifetime is exceeded before a refresh LSP arrives, the LSP is dropped from the database.
You might need to adjust the maximum LSP lifetime if you change the LSP refresh interval with the lsp-refresh-interval (IP) command. 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.
You might prefer higher values for each command in order to reduce control traffic, at the expense of holding stale LSPs from a crashed or unreachable router in the database longer (thus wasting memory) or increasing the risk of undetected bad LSPs staying active (very rare).
Examples
The following example configures an LSP lifetime of 40 minutes:
router isismax-lsp-lifetime 2400Related Commands
net
To configure an Intermediate System-to-Intermediate System (IS-IS) network entity title (NET) for the routing process, use the net command in router configuration mode. To remove a NET, use the no form of this command.
net network-entity-title
no net network-entity-title
Syntax Description
network-entity-title
NET that specifies the area address and the system ID for an IS-IS routing process. This argument can be either an address or a name.
Defaults
No NET is configured and the IS-IS process will not start. A NET is mandatory.
Command Modes
Router configuration
Command History
10.0
This command was introduced.
12.0(5)T
This command was modified to include multiarea IS-IS routing.
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 Connectionless Network Service (CLNS) routing enabled), a NET must still be configured to define the router system ID and area ID.
Multiple NETs per router are allowed, with a maximum of three. 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 more 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 more 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 0000.0c11.1110 and area ID 47.0004.004d.0001:
router isis CHESNUTnet 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 Tunnel529ip address 10.0.0.5 255.255.255.0ip router isis BBclns router isis BBinterface Ethernet1ip address 10.1.1.5 255.255.255.0ip router isis A3253-01clns router isis A3253-01!interface Ethernet2ip address 10.2.2.5 255.255.255.0ip router isis A3253-02clns router isis A3253-02...router isis BB ! Defaults to "is-type level-1-2"net 49.2222.0000.0000.0005.00!router isis A3253-01net 49.0553.0001.0000.0000.0005.00is-type level-1!router isis A3253-02net 49.0553.0002.0000.0000.0005.00is-type level-1Related Commands
Configures the routing level for an instance of the IS-IS routing process.
Enables the IS-IS routing protocol and specifies an IS-IS process.
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. This command displays the output from different areas as a string or additional white space. To disable this output format, use the no form of the command .
partition avoidance area-tag
no partition avoidance area-tag
Syntax Description
Defaults
By default the partition avoidance command is disabled.
Command Modes
Router configuration
Command History
Usage Guidelines
When the partition avoidance command is enabled, a multiarea router withdraws a Level 1 area prefix from the Level 2 backbone when it no longer has any active adjacencies to that Level 1 area. This withdrawal prevents the Level 1 area from appearing to be partitioned within the Level 2 backbone.
In International 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.
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 Finance to stop advertising the prefix for the area named "area1" with the router no longer has any active adjacencies to area1.
router isis Financepartition avoidance area1Related Commands
Configures the routing level for an instance of the IS-IS routing process.
Enables the IS-IS routing protocol and specifies an IS-IS process.
prc-interval
To customize IS-IS throttling of partial route calculations (PRC), use the prc-interval command in router configuration mode. To restore default values, use the no form of this command.
prc-interval prc-max-wait [prc-initial-wait prc-second-wait]
no prc-interval
Syntax Description
Defaults
prc-max-wait: 5 seconds
prc-initial-wait: 2000 milliseconds
prc-second-wait: 5000 millisecondsCommand Modes
Router configuration
Command History
Usage Guidelines
PRC is the software's process of calculating routes without performing an 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 RIB.
The following description will help you determine whether to change the default values of this command:
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Examples
The following example configures intervals for SPF calculations, PRC, and LSP generation:
router isisspf-interval 5 10 20prc-interval 5 10 20lsp-gen-interval 2 50 100router 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
Defaults
The router isis command is disabled.
Command Modes
Global configuration
Command History
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.
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, for example) 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 Release 12.0 of the Cisco IOS software, 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:
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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 0 and serial 0 interfaces. The IP prefix assigned to Ethernet 0 will be advertised to other IS-IS routers:
router isisnet 01.0001.0000.0000.0002.00is-type level-1!interface ethernet 0ip address 10.1.1.1 255.255.255.0ip router isis!interface serial 0ip unnumbered ethernet0ip router isisThe following example starts IS-IS routing with the optional area-tag argument, where CHESNUT is the value for the area-tag argument:
router isis CHESNUTThe following example specifies IS-IS as an IP routing protocol for a process named Finance, and specifies that the Finance process will be routed on interfaces Ethernet 0 and serial 0:
router isis Financenet 49.0001.aaaa.aaaa.aaaa.00interface Ethernet 0ip router isis Financeinterface serial 0ip router isis FinanceRelated Commands
set-overload-bit
To configure the router to signal other routers not to use it as an intermediate hop in their shortest path first (SPF) calculations, use the set-overload-bit command in router configuration mode. To remove the designation, use the no form of this command.
set-overload-bit [on-startup {seconds | wait-for-bgp}]
no set-overload-bit
Syntax Description
Defaults
The overload bit is not set.
Command Modes
Router configuration
Command History
Usage Guidelines
This command forces the router to set the overload bit (also known as the hippity bit) in its nonpseudonode link-state packets. 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 CLNS prefixes directly connected to this router will be still be reachable.
This command can be useful when you want to connect a router to an ISIS network, but do not want real traffic flowing through it under any circumstances. Examples are:
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Unless you specify the on-startup keyword, this command sets the overload bit immediately.
Examples
The following example sets the overload bit upon startup and until BGP has converged:
interface Ethernet0ip address 10.1.1.1 255.255.255.0ip router isisrouter isisnet 49.0001.0000.0000.0001.00set-overload-bit on-startup wait-for-bgprouter bgp 100show isis database
To display the Intermediate System-to-Intermediate System (IS-IS) link state database, use the show isis database command in EXEC mode.
show isis area-tag database [level-1] [level-2] [l1] [l2] [detail] [lspid]
Syntax Description
Command Modes
EXEC
Command History
Usage Guidelines
Each of the options shown in brackets for this command can be entered in an arbitrary string within the same command entry. For example, the following are both valid command specifications and provide the same output: show isis database detail l2 and show isis database l2 detail.
Examples
The following is sample output from the show isis database command when it is specified with no options or as show isis database:
Router# show isis databaseIS-IS Level-1 Link State DatabaseLSPID LSP Seq Num LSP Checksum LSP Holdtime ATT/P/OL0000.0C00.0C35.00-00 0x0000000C 0x5696 792 0/0/00000.0C00.40AF.00-00* 0x00000009 0x8452 1077 1/0/00000.0C00.62E6.00-00 0x0000000A 0x38E7 383 0/0/00000.0C00.62E6.03-00 0x00000006 0x82BC 384 0/0/00800.2B16.24EA.00-00 0x00001D9F 0x8864 1188 1/0/00800.2B16.24EA.01-00 0x00001E36 0x0935 1198 1/0/0IS-IS Level-2 Link State DatabaseLSPID LSP Seq Num LSP Checksum LSP Holdtime ATT/P/OL0000.0C00.0C35.03-00 0x00000005 0x04C8 792 0/0/00000.0C00.3E51.00-00 0x00000007 0xAF96 758 0/0/00000.0C00.40AF.00-00* 0x0000000A 0x3AA9 1077 0/0/0Table 65 describes significant fields shown in the display
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Example Using Show IS-IS Database Detail
The following is sample output from the show isis database detail command.
Router# show isis database detailIS-IS Level-1 Link State DatabaseLSPID LSP Seq Num LSP Checksum LSP Holdtime ATT/P/OL0000.0C00.0C35.00-00 0x0000000C 0x5696 325 0/0/0Area Address: 47.0004.004D.0001Area Address: 39.0001Metric: 10 IS 0000.0C00.62E6.03Metric: 0 ES 0000.0C00.0C35--More--0000.0C00.40AF.00-00* 0x00000009 0x8452 608 1/0/0Area Address: 47.0004.004D.0001Metric: 10 IS 0800.2B16.24EA.01Metric: 10 IS 0000.0C00.62E6.03Metric: 0 ES 0000.0C00.40AFIS-IS Level-2 Link State DatabaseLSPID LSP Seq Num LSP Checksum LSP Holdtime ATT/P/OL0000.0C00.0C35.03-00 0x00000005 0x04C8 317 0/0/0Metric: 0 IS 0000.0C00.0C35.00--More--0000.0C00.3E51.00-00 0x00000009 0xAB98 1182 0/0/0Area Address: 39.0004Metric: 10 IS 0000.0C00.40AF.00Metric: 10 IS 0000.0C00.3E51.05As the output shows, in addition to the information displayed with show isis database, the show isis database detail command displays the contents of each LSP.
Table 66 describes the additional fields shown in the display.
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Example Using Show IS-IS Database Detail Displaying IP Addresses
The following is additional sample output from the show isis database detail command.This 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 detail l2IS-IS Level-2 Link State DatabaseLSPID LSP Seq Num LSP Checksum LSP Holdtime ATT/P/OL0000.0C00.1111.00-00* 0x00000006 0x4DB3 1194 0/0/0Area Address: 39.0001NLPID: 0x81 0xCCIP Address: 160.89.64.17Metric: 10 IS 0000.0C00.1111.09Metric: 10 IS 0000.0C00.1111.08Metric: 10 IP 160.89.65.0 255.255.255.0Metric: 10 IP 160.89.64.0 255.255.255.0Metric: 0 IP-External 10.0.0.0 255.0.0.0Table 67 describes the additional field 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-log command in EXEC mode.
show isis lsp-log
Syntax Description
This command has no arguments or keywords.
Command Modes
EXEC
Command History
Examples
The following is sample output from the show isis lsp-log command:
Router# show isis lsp-logLevel 1 LSP logWhen Count Interface Triggers07:05:18 3 CONFIG NEWADJ DIS07:05:13 2 Ethernet0 NEWADJ DIS07:04:43 1 ATTACHFLAG07:01:38 2 Ethernet0 IPUP07:01:33 2 Loopback0 CONFIG07:01:24 1 Ethernet0 DELADJ07:01:17 2 Ethernet0 DIS ES07:01:02 1 Ethernet0 NEWADJ07:00:57 2 Ethernet0 NEWADJ DISLevel 2 LSP logWhen Count Interface Triggers07:05:24 2 CONFIG NEWADJ07:05:23 1 Ethernet0 NEWADJ07:05:18 1 Ethernet0 DIS07:05:00 1 Serial0 NEWADJ07:01:44 2 Ethernet0 IPUP07:01:39 3 Loopback0 CONFIG DELADJ07:01:30 1 Ethernet0 DELADJ07:01:25 1 Serial0 NEWADJ07:00:56 1 IPIA07:00:47 2 AREASET IPIATable 68 describes the fields shown in the display.
show isis spf-log
To display how often and why the router has run a full shortest path first (SPF) calculation, use the show isis spf-log user command in EXEC mode.
show isis area-tag spf-log
Syntax Description
Command Modes
User EXEC
Command History
Examples
The following is sample output from the show isis spf-log command:
Router# show isis spf-logLevel 1 SPF logWhen Duration Nodes Count Last trigger LSP Triggers00:15:46 3124 40 1 milles.00-00 TLVCODE00:15:24 3216 41 5 milles.00-00 TLVCODE NEWLSP00:15:19 3096 41 1 deurze.00-00 TLVCODE00:14:54 3004 41 2 milles.00-00 ATTACHFLAG LSPHEADER00:14:49 3384 41 1 milles.00-01 TLVCODE00:14:23 2932 41 3 milles.00-00 TLVCODE00:05:18 3140 41 1 PERIODIC00:03:54 3144 41 1 milles.01-00 TLVCODE00:03:49 2908 41 1 milles.01-00 TLVCODE00:03:28 3148 41 3 bakel.00-00 TLVCODE TLVCONTENT00:03:15 3054 41 1 milles.00-00 TLVCODE00:02:53 2958 41 1 mortel.00-00 TLVCODE00:02:48 3632 41 2 milles.00-00 NEWADJ TLVCODE00:02:23 2988 41 1 milles.00-01 TLVCODE00:02:18 3016 41 1 gemert.00-00 TLVCODE00:02:14 2932 41 1 bakel.00-00 TLVCONTENT00:02:09 2988 41 2 bakel.00-00 TLVCONTENT00:01:54 3228 41 1 milles.00-00 TLVCODE00:01:38 3120 41 3 rips.03-00 TLVCONTENTTable 69 describes the fields in the display.
Table 69 show isis spf-log Field Descriptions
When
How long ago (hh:mm:ss) 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 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 give 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 Table 70.
Table 70 gives a list of possible triggers of a full SPF calculation.
show isis topology
To display a list of all connected routers in all areas, use the show isis topology command in EXEC mode.
show isis area-tag topology [level-1] [level-2] [host-nsap]
Syntax Description
Command Modes
EXEC
Command History
12.0(5)T
This command was introduced.
12.1
The level-1 and level-2 keywords and the host-nsap argument were added.
Usage Guidelines
Use the show isis topology EXEC command to verify the presence and connectivity between all routers in all areas.
Examples
The following is sample output from the show isis topology command:
Router# show isis topologyIS-IS paths to level-1 routersSystem Id Metric Next-Hop Interface SNPARouter_A --Router_B 10 Router_B Et0 00e0.b064.46ecIS-IS paths to level-2 routersSystem Id Metric Next-Hop Interface SNPARouter_A --Router_B 10 Router_B Et0 00e0.b064.46ecRouter_C 20 Router_B Et0 00e0.b064.46ecRouter_D Se0 DLCI 100Router_D Se1 *HDLC*Router_D 10 Router_D Se0 DLCI 100Router_D Se1 *HDLC*Table 71 describes the fields shown in the display.
Related Commands
spf-interval
To customize 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
Defaults
spf-max-wait: 10 seconds
spf-initial-wait: 5500 milliseconds
spf-second-wait: 5500 millisecondsCommand Modes
Router configuration
Command History
Usage Guidelines
The following description will help you determine whether to change the default values of this command:
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SPF throttling is not a dampening mechanism; that is, SPF throttling does not prevent SPF calculations or mark any route, interface, or router as down. SPF throttling simply increases the intervals between SPF calculations.
Examples
The following example configures intervals for SPF calculations, PRC, and LSP generation:
router isisspf-interval 5 10 20prc-interval 5 10 20lsp-gen-interval 2 50 100summary-address (IS-IS)
To create aggregate addresses for Intermediate System-to-Intermediate System (IS-IS) or Open Shortest Path First (OSPF), use the summary-address command in router configuration mode. Use the no form of the command to restore the default.
summary-address address mask {level-1 | level-1-2 | level-2}
no summary-address address mask {level-1 | level-1-2 | level-2}
Syntax Description
Defaults
All redistributed routes are advertised individually.
Command Modes
Router configuration
Command History
Usage Guidelines
Multiple 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. It also helps 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 forth. This example advertises only 10.1.0.0 into our IS-IS Level 1 Link State PDU.
router isisnet 01.0000.0000.0001.00redistribute rip level-1 metric 40summary-address 10.1.0.0 255.255.0.0 level-1