Segment Routing with IS-IS Protocol

About IS-IS

IS-IS is an Interior Gateway Protocol (IGP) based on Standardization (ISO)/International Engineering Consortium (IEC) 10589 and RFC 1995. Cisco NX-OS supports Internet Protocol version 4 (IPv4) and IPv6. IS-IS is a dynamic link-state routing protocol that can detect changes in the network topology and calculate loop-free routes to other nodes in the network. Each router maintains a link-state database that describes the state of the network and sends packets on every configured link to discover neighbors. IS-IS floods the link-state information across the network to each neighbor. The router also sends advertisements and updates on the link-state database through all the existing neighbors

Segment routing on the IS-IS protocol supports the following:

  • IPv4

  • Level 1, level 2, and multi-level routing

  • Prefix SIDs

  • Multiple IS-IS instances on the same loopback interface for domain border nodes

  • Adjacency SIDs for adjacencies

Configuring Segment Routing with IS-IS Protocol

You can configure segment routing with IS-IS protocol.

Before you begin

IS-IS segment routing is fully enabled when the following conditions are met:

  • The mpls segment-routing feature is enabled.

  • The IS-IS feature is enabled.

  • Segment routing is enabled for at least one address family under IS-IS.

Procedure

  Command or Action Purpose

Step 1

configure terminal

Enters global configuration mode.

Step 2

router isis instance-tag

Creates a new IS-IS instance with the configured instance tag.

Step 3

net network-entity-title

Configures the NET for this IS-IS instance.

Step 4

address-family ipv4 unicast

Enters address family configuration mode.

Step 5

segment-routing mpls

Configures segment routing with IS-IS protocol.

Note

 

  • The IS-IS command is supported only on the IPv4 address family. It is not supported on the IPv6 address family.

  • Redistribution is not supported from any other protocol to ISIS for the SR prefixes. You need to enable ip router isis command on all the prefix SID interfaces.