ISIS IPv6 Multi Topology


IS IS IPv6 Multi-topology is a way to run IPv6 address-family during a migration period to IPv6. There are two different topologies and SPF calculated for each address-family.

IS IS IPv6 Multi-Topology

  • After making the change clear the ISIS neighbor sessions.
  • This method is used when transitioning to IPv6 or when different routing topologies are necessary for IPv6.
  • Costs can be modified per address-family instead for links like in single-topology.
  • By default IOS-XR operates in multi-topology, which is opposite from IOS, which operates in single-topology.
  • For Multi-topology to work wide-metric is required.
  • There is not good way to check which topology method is one. The best is to look in the isis database to see if any IPv6 addresses exist, if not then there might be a mismatch. Additionally, by using ** log-adjacency-changes all** the user can be notified of mismatch.
%CLNS-5-ADJCHANGE: ISIS: Adjacency to R2 (FastEthernet0/0) Down, clear clns nbr cmd(non-iih)
%CLNS-5-ADJCLEAR: ISIS: All adjacencies cleared
%CLNS-5-ADJCHANGE: ISIS: Adjacency to R2 (FastEthernet0/0) topology mismatched, TID (2) not in remote IIH
%CLNS-5-ADJCHANGE: ISIS: Adjacency to R2 (FastEthernet0/0) topology changed, TID (2) added, locally configured

Relevant IOS Commands


Configures multi-topology feature.

R2(config)#router isis 1
R2(config-router)#address-family ipv6 

R2(config-router-af)#        multi-topology

Show isis database detail

Show that multi-topology is used for IPv6.

show isis database detail

Relevant XR Commands


Configures multi-topology feature by disabling single-topology.

RP/0/0/CPU0:XR12(config)#router isis 1
RP/0/0/CPU0:XR12(config-isis)#address-family ipv6

RP/0/0/CPU0:XR12(config-isis-af)#no single-topology


rating: 0+x
Unless otherwise stated, the content of this page is licensed under Creative Commons Attribution-ShareAlike 3.0 License