IS-IS Command Reference

This command administratively disables the entity. When disabled, an entity does not change, reset, or remove any configuration settings or statistics. Many entities must be explicitly enabled using the no shutdown command.

The operational state of the entity is disabled as well as the operational state of any entities contained within. Many objects must be shut down before they can be deleted.

Unlike other commands and parameters where the default state is not indicated in the configuration file, shutdown and no shutdown are always indicated in system-generated configuration files.

The no form of the command puts an entity into the administratively enabled state.

This command activates an IS-IS instance on the router and enables access to the context to define IS-IS parameters.

Instance 0, the base instance, is enabled when the isis command is run without specifying an isis-instance. Multiple IS-IS instances are enabled by including an isis-instance value.

The no form of the command deletes the IS-IS instance and removes all configuration parameters.

This command configures the area ID portion of the Network Service Access Point (NSAP) address, which identifies a point of connection to the network, such as a router interface.

Addresses in the IS-IS protocol are based on the ISO NSAP addresses and Network Entity Titles (NETs), not IP addresses. NET addresses are constructed similarly to NSAPs with the exception that the selector ID is always 00. NET addresses are exchanged in Hello and LSP PDUs. All NET addresses configured on the node are advertised to its neighbors.

Up to three area addresses can be configured.

NSAP addresses are divided into three parts. Only the area ID portion is configurable:

For level 1 interfaces, neighbors can have different area IDs, but they must have at least one area ID (AFI + area) in common. Sharing a common area ID, they become neighbors and area merging between the potentially different areas can occur.

For level 2 interfaces, neighbors can have different area IDs. However, if they have no area IDs in common, they become only level 2 neighbors and only level 2 LSPs are exchanged.

For level 1/2 interfaces, neighbors can have different area IDs. If they have at least one area ID (AFI + area) in common, they become neighbors. In addition to exchanging level 2 LSPs, area merging between potentially different areas can occur.

If multiple area-id commands are entered, the system ID of all subsequent entries must match the system ID of the first area address.

The no form of the command removes the area address.

This command sets an authentication check to reject PDUs that do not match the type or key requirements.

The default behavior when authentication is configured is to reject all IS-IS protocol PDUs that have a mismatch in either the authentication type or authentication key.

When no authentication-check is configured, authentication PDUs are generated and IS-IS PDUs are authenticated on receipt. However, although mismatches cause an event to be generated, the mismatches will not be rejected.

This command sets the authentication key used to verify PDUs sent by neighboring routers on the interface. Neighboring routers use passwords to authenticate PDUs sent from an interface. For authentication to work, both the authentication key and the authentication type on a segment must match. The authentication-type command must also be entered.

To configure authentication on the global level, configure this command in the config>router>isis context. When this parameter is configured on the global level, all PDUs are authenticated, including the Hello PDU.

To override the global setting for a specific level, configure the authentication-key command in the config>router>isis>level context. When configured within the specific level, Hello PDUs are not authenticated.

By default, no authentication key is configured.

The no form of the command removes the authentication key.

This command enables either simple password or message-digest authentication in the global IS-IS or IS-IS level context. Both the authentication key and the authentication type on a segment must match. The authentication-key command must also be entered.

Configure the authentication type at the global level in the config>router>isis context. Configure or override the global setting by configuring the authentication type in the config>router>isis>level context.

The no form of the command disables authentication.

This command enables authentication of individual IS-IS packets of complete sequence number PDUs (CSNPs).

The no form of the command suppresses authentication of CSNP packets.

This command disables the IGP-LDP synchronization feature on all interfaces participating in the OSPF or IS-IS routing protocol. When this command is executed, IGP immediately advertises the actual value of the link cost for all interfaces that have the IGP-LDP synchronization enabled if the currently advertised cost is different. IGP-LDP synchronization will then be disabled for all interfaces. This command does not delete the interface configuration.

The no form of this command restores the default settings and re-enables IGP-LDP synchronization on all interfaces participating in the OSPF or IS-IS routing protocol and for which the ldp-sync-timer is configured (refer to the 7705 SAR OS Router Configuration Guide for information on configuring the ldp-sync-timer).

This command associates export route policies to determine which routes are exported from the route table to IS-IS.

If no export policy is specified, non-IS-IS routes are not exported from the routing table manager to IS-IS.

If multiple policy names are specified, the policies are evaluated in the order they are specified. The first policy that matches is applied. If multiple export commands are issued, the last command entered will override the previous command. A maximum of five policy names can be specified.

The no form of the command removes all policies from the configuration.

Refer to the 7705 SAR OS Router Configuration Guide for information on defining route policies.

This command configures the preference for IS-IS external routes for the IS-IS level. The preference for internal routes is set with the preference command.

The command configures the preference level for either level 1 or level 2 external routes. The default preferences are listed in Table 37.

A route can be learned by the router from different protocols, in which case, the costs are not comparable. When this occurs, the preference is used to decide which route will be used.

Different protocols should not be configured with the same preference. If this occurs, the tiebreaker is based on the default preferences as listed in Table 37.

If multiple routes are learned with an identical preference using the same protocol, the lowest-cost route is used. If multiple routes are learned with an identical preference using the same protocol and the costs (metrics) are equal, the decision of which route to use is determined by the configuration of ECMP in the config>router context. Refer to the 7705 SAR OS Router Configuration Guide for information on ECMP.

Note: To configure a preference for static routes, use the config>router>static-route command. Refer to the 7705 SAR OS Router Configuration Guide for information.

The no form of the command reverts to the default value.

This command enables authentication of individual IS-IS Hello PDUs.

The no form of the command suppresses authentication of Hello PDUs.

This command specifies whether the Instance Identifier (IID) TLV is enabled or disabled for this IS-IS instance so an interface can be used in multiple IS-IS instances.

When enabled, each IS-IS instance marks its packets with the IID TLV containing its unique 16-bit IID for the routing domain. You must use a shutdown/no shutdown command sequence on the IS-IS instance to make the change operational.

The no form of the command disables the IID TLV marking of packets.

This command creates the context to configure IS-IS level 1 or level 2 area attributes.

To reset global and/or interface level parameters to the default, the following commands must be entered independently:

This command configures the routing level for the IS-IS instance.

An IS-IS router and IS-IS interface can operate at level 1, level 2, or both level 1 and level 2.

A level 1 adjacency can be established if there is at least one area address shared by this router and a neighbor. A level 2 adjacency cannot be established over this interface.

A level 1/2 adjacency is created if the neighbor is also configured as a level 1/2 router and has at least one area address in common. A level 2 adjacency is established if there are no common area IDs.

A level 2 adjacency is established if another router is configured as a level 2 or level 1/2 router with interfaces configured as level 1/2 or level 2. Level 1 adjacencies will not established over this interface.

Table 38 lists capability combinations and the potential adjacencies that can be formed.

The no form of the command removes the level capability from the configuration.

This command sets the time interval for LSPs originated by the router to be considered valid by other routers in the domain.

Each LSP received is maintained in an LSP database until the LSP lifetime expires, unless the originating router refreshes the LSP. By default, each router refreshes its LSPs every 20 min (1200 s) so that other routers will not age out the LSP.

The LSP lifetime value should be greater than the refresh value; otherwise, the LSP will be aged out before being refreshed.

The no form of the command reverts to the default value.

This command is used to customize the throttling of IS-IS LSP generation. Timers that determine when to generate the first, second, and subsequent LSPs can be controlled with this command. Subsequent LSPs are generated at increasing intervals of the lsp-second-wait timer until a maximum value is reached.

This command enables the submission of routes into the multicast Route Table Manager (RTM) by IS-IS.

The no form of the command disables the submission of routes into the multicast RTM.

This command administratively sets the IS-IS router to operate in the overload state for a specific time period, in seconds, or indefinitely.

During normal operation, the router may be forced to enter an overload state due to a lack of resources. When in the overload state, the router is only used if the destination is reachable by the router and will not be used for other transit traffic.

If a time period is specified, the overload state persists for the configured length of time. If no time is specified, the overload state operation is maintained indefinitely.

The overload command can be useful in circumstances where the router is overloaded or used prior to executing a shutdown command to divert traffic around the router.

The no form of the command causes the router to exit the overload state.

When the router is in an overload state, the router is used only if there is no other router to reach the destination. This command configures IS-IS in the overload state upon bootup until one of the following events occurs:

The no overload command does not affect the overload-on-boot function. If the overload state is cleared with the no overload command, the router will still re-enter the overload state after rebooting.

If no timeout is specified, IS-IS will go into the overload state indefinitely after a reboot. After the reboot, the IS-IS status will display a permanent overload state:

This state can be cleared with the no overload command.

If a timeout value is specified, IS-IS will go into the overload state for the configured timeout after a reboot. After the reboot, the IS-IS status will display the remaining time that the system stays in overload:

The overload state can be cleared before the timeout expires with the no overload command.

The no form of the command removes the overload-on-boot functionality from the configuration.

This command configures the preference for IS-IS level 1 or level 2 internal routes.

A route can be learned by the router from different protocols, in which case, the costs are not comparable. When this occurs, the preference is used to decide which route will be used.

Different protocols should not be configured with the same preference. If this occurs, the tiebreaker is based on the default preferences as listed in Table 37. If multiple routes are learned with an identical preference using the same protocol and the costs (metrics) are equal, the decision of which route to use is determined by the configuration of ECMP in the config>router context. Refer to the 7705 SAR OS Router Configuration Guide for information on ECMP.

The no form of the command reverts to the default value.

This command enables authentication of individual IS-IS packets of partial sequence number PDUs (PSNPs).

The no form of the command suppresses authentication of PSNP packets.

This command configures the reference bandwidth for the costing of interfaces based on their underlying link speed.

In order to calculate the lowest cost to reach a specific destination, each configured level on each interface must have a cost. If the reference bandwidth is defined, the cost is calculated using the following formula:

cost = reference bandwidth/bandwidth

If the reference bandwidth is configured as 10 Gbytes (10 000 000 000), a 100 Mb/s interface has a default metric of 100. In order for metrics in excess of 63 to be configured, wide metrics must be deployed (see the wide-metrics-only command).

If the reference bandwidth is not configured, all interfaces have a default metric of 10.

The no form of the command returns the reference bandwidth to the default value.

This command defines the maximum interval, in seconds and milliseconds, between two consecutive SPF calculations. Timers that determine when to initiate the first, second, and subsequent SPF calculations after a topology change occurs can be controlled with this command. Subsequent SPF runs (if required) will occur at doubling intervals of the spf-second-wait interval. For example, if the spf-second-wait interval is 1000, the next SPF will run after 2000 ms, and the next SPF after that will run after 4000 ms, and so on, until it reaches the spf-wait value. The SPF interval will stay at the spf-wait value until there are no more SPF runs scheduled in that interval. After a full interval without any SPF runs, the SPF interval will drop back to spf-initial-wait.

The timer must be entered in increments of 100 ms. Values entered that do not match this requirement will be rejected.

The no form of this command returns to the default.

This command creates summary addresses.

This command enables traffic engineering and determines if IGP shortcuts are required.

The no form of the command disables traffic-engineered route calculations.

This command allows one IGP to import its routes into the multicast RTM (also known as the RPF RTM [Reverse Path Forwarding - Route Table Manager]) while another IGP imports routes only into the unicast RTM. Import policies can redistribute routes from an IGP protocol into the RPF RTM. By default, the IGP routes will not be imported into the RPF RTM, since such an import policy must be explicitly configured.

The no form of the command enables importing IGP routes into the RPF RTM.

This command enables the exclusive use of wide metrics in the LSPs for the level number. Narrow metrics can have values between 1 and 63. IS-IS can generate two TLVs, one for the adjacency and one for the IP prefix. In order to support traffic engineering, wider metrics are required. When wide metrics are used, a second pair of TLVs are added for the adjacency and the IP prefix.

By default, both sets of TLVs are generated. When wide-metrics-only is configured, IS-IS only generates the pair of TLVs with wide metrics for that level.

The no form of the command reverts to the default value.

This command creates the context to configure an IS-IS interface.

When an area is defined, the interfaces belong to that area. Interfaces cannot belong to other areas.

If the interface is a POS channel, the OSI Network Layer Control Protocol (OSINLCP) is enabled when the interface is created and removed when the interface is deleted.

The no form of the command deletes the IS-IS interface configuration for this interface. The shutdown command in the config>router>isis>interface context can be used to disable an interface without removing the configuration for the interface.

This command enables the use of bidirectional forwarding (BFD) to control IPv4 adjacencies. By enabling BFD on a given IS-IS interface, the state of the interface is tied to the state of the BFD session between the local node and the remote node. The parameters used for BFD are set via the BFD command under the IP interface.

The no form of this command removes BFD from the associated IPv4 adjacency.

This command configures the interval, in seconds, to send complete sequence number PDUs (CSNPs) from the interface. IS-IS must send CSNPs periodically.

The no form of the command reverts to the default value.

This command configures the authentication key (password) for Hello PDUs. Neighboring routers use the password to verify the authenticity of Hello PDUs sent from this interface. Both the hello authentication key and the hello authentication type on a segment must match. The hello-authentication-type command must also be entered.

To configure the hello authentication key for all levels configured for the interface, use the hello-authentication-key command in the config>router>isis>interface context.

To configure or override the hello authentication key for a specific level, use the hello-authentication-key command in the config>router>isis>interface>level context.

If both IS-IS authentication and hello-authentication are configured, Hello messages are validated using hello authentication. If only IS-IS authentication is configured, it will be used to authenticate all IS-IS protocol PDUs, including Hello PDUs.

The no form of the command removes the hello authentication key from the configuration.

This command enables Hello authentication at either the interface or level context. Both the hello authentication key and the hello authentication type on a segment must match. The hello-authentication-key command must also be entered.

To configure the hello authentication type for all levels configured for the interface, use the hello-authentication-type command in the config>router>isis>interface context.

To configure or override the hello authentication type for a specific level, use the hello-authentication-type command in the config>router>isis>interface>level context.

The no form of the command disables Hello PDU authentication.

This command configures the interval between IS-IS Hello PDUs issued on the interface at this level.

The no form of this command reverts to the default value.

This command configures the number of missing Hello PDUs from a neighbor after which the router declares the adjacency down.

The no form of this command reverts to the default value.

This command configures the interface type to be either broadcast or point-to-point.

Use this command to set the interface type of an Ethernet link to point-to-point to avoid having to carry the broadcast adjacency maintenance overhead of the Ethernet link, provided the link is used as a point-to-point link.

If the interface type is not known when the interface is added to IS-IS, and the IP interface is subsequently bound (or moved) to a different interface type, this command must be entered manually.

The no form of the command reverts to the default value.

This command configures the interval between link-state PDUs (LSPs) sent from this interface. Controlling the time between LSPs ensures that adjacent neighbors are not being bombarded with excessive data.

A value of 0 means that no LSPs are sent from the interface.

The no form of the command reverts to the default value.

This command assigns an interface to a mesh group. Mesh groups limit the amount of flooding that occurs when a new or changed LSP is advertised throughout an area.

All routers in a mesh group should be fully meshed. When LSPs need to be flooded, only a single copy is received rather than one copy per neighbor.

To create a mesh group, configure the same mesh group value for each interface that is part of the mesh group. All routers must have the same mesh group value configured for all interfaces that are part of the mesh group.

To prevent an interface from flooding LSPs, the optional blocked parameter can be specified.

Caution: Configure mesh groups carefully. It is easy to create isolated islands that will not receive updates if other links fail.

The no form of the command removes the interface from the mesh group.

This command configures the metric used for the level on this IS-IS interface.

To calculate the lowest cost to reach a given destination, each configured level on each interface must have a cost. The costs for each level on an interface may be different.

If the metric is not configured, the default value of 10 is used unless the reference-bandwidth is configured.

The no form of the command reverts to the default value.

This command adds the passive attribute to the IS-IS interface, which causes the interface to be advertised as an IS-IS interface without running the IS-IS protocol. Normally, only interface addresses that are configured for IS-IS are advertised as IS-IS interfaces at the level that they are configured.

If the passive mode is enabled, the interface or the interface at the specified level ignores ingress IS-IS protocol PDUs and will not transmit IS-IS protocol PDUs.

The no form of the command removes the passive attribute.

This command configures the priority of the IS-IS interface that is used in an election of the designated router (DIS) on a multi-access network.

This parameter is only used if the interface is a broadcast type.

The priority is included in Hello PDUs transmitted by the interface on a multi-access network. The router with the highest priority becomes the designated router. The designated router is responsible for sending LSPs about the network and the routers attached to it.

The no form of the command reverts to the default value.

This command specifies the interval, in seconds, that IS-IS will wait before retransmitting an unacknowledged LSP to an IS-IS neighbor.

If the retransmit interval expires and no acknowledgment has been received, the LSP will be retransmitted.

The no form of this command reverts to the default interval.