You can change the administrative distance for IPv6 IS-IS routes. The following task changes the administrative distance for the IS-IS IPv6 unicast address family.
device# configure terminal
device(config)# router isis
device(config-isis-router)# address-family ipv6 unicast
device(config-router-isis-ipv6u)# distance 60
The following example sets an administrative distance of 60 for the IPv6 unicast address family.
device# configure terminal device(config)# router isis device(config-isis-router)# address-family ipv6 unicast device(config-router-isis-ipv6u)# distance 60