User guide

Configuring IS-IS Multi-Topology IS-IS Overview

OmniSwitch AOS Release 7 Advanced Routing Configuration Guide March 2015 page 3-35

For backwards compatibility with non M-ISIS aware routers, even if M-ISIS capability is enabled, AOS

IS-IS will continue to exchange IPv4 prefixes in the default IPv4 reachability TLVs (and not in the M-IS-

IS TLVs in MT ID 0). SPF processing for IPv4 will include default IPv4 Reachability TLVs along with

those received in MT ID 0 TLVs (if any).

Verify M-ISIS Configuration

Use the show ip isis status and show ip isis adjacency commands to view the M-ISIS configuration

details.

M-ISIS Configuration Scenario

In the above scenario, when M-ISIS is configured, the IPV6 traffic sent from PC2 to PC1 is sent along the

green path even though orange path is the shortest path with minimum hops. M-ISIS distinguishes

between IPv4 and IPv6 topologies, the dual-stack routers performs SPF calculation separately for IPv4

and IPv6. That is, the MT-specific SPF calculation for IPv6 excludes router IPV4 only router thereby

preventing the black-holing.