IS-IS Configuration Guide for Cisco 8000 Series Routers, Cisco IOS XR Releases

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IS-IS Configuration Guide for Cisco 8000 Series Routers, Cisco IOS XR Releases

Enable multicast IS-IS topology

Updated: June 9, 2026

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Provides instructions for enabling and managing IS-IS topologies by assigning unique topology names and IDs, supporting advanced routing for IPv4 and IPv6 multicast environments within multiple routing domains.

Establish and distinguish IS-IS topologies in a routing domain by associating a topology ID with a named topology.

Use this task to create and manage multiple routing domains within IS-IS by assigning unique topology names and IDs. This enables advanced routing features and supports both IPv4 and IPv6 multicast topologies.

Before you begin

  • Ensure you have access to the device in configuration mode.

  • Prepare the instance ID, topology name, and numeric topology ID (value between 6 and 4095).

Follow these steps to enable an IS-IS topology:

Procedure

1.

Enter IS-IS router configuration mode:

Example:

Router(config)# router isis purple
2.

Associate a named topology with an address family:

Example:

Router(config-isis)# address-family ipv4 multicast topology green
3.

Assign the numeric topology ID to the named topology:

Example:

Router(config-isis-af)# toplogy-id 122

ID must be in the range 6 to 4095.

Assign an interface to an IS-IS topology

Enable IS-IS multi-topology routing by associating interfaces with distinct logical topologies for improved network segmentation and control.

Use this task when you want to segregate network routing into separate topologies, such as for Layer 3 VPNs or multicast domains. Assigning interfaces to individual IS-IS topologies allows separate route computation and advertisement for each topology.

Before you begin

  • Verify you have privileged EXEC access on the router.

  • Ensure IS-IS routing is enabled and properly initialized on the device.

  • Prepare the IS-IS instance ID, network entity title (NET), interface details, and desired topology names.

Procedure

1.

Enter IS-IS router configuration mode:

Example:

Routing(config)# router isis purple
2.

Configure the network entity title for the IS-IS instance:

Example:

Routing(config-isis)# net netname

This sets the ISO NET used for IS-IS routing.
3.

Specify the interface to associate with the IS-IS instance:

Example:

Routing(config-isis)# interface gigabitethernet 0/3/0/0

This places the interface into IS-IS interface configuration mode.
4.

Assign the interface to a specific address family and topology:

Example:

Routing(config-isis-if)# address-family ipv4 multicast topology green

This places the interface into the desired IS-IS topology and address family.
5.

Repeat steps 3 and 4 for each additional interface and topology as needed.

The interfaces are now associated with the specified IS-IS topologies. Verify the configuration using commands such as show isis interface or show isis topology to confirm correct placement.