IPv6 protocol-support consistency checks

An IS-IS single topology must be configured to run the same set of network protocols (IPv4 IS-IS only, IPv6 IS-IS only, or both IPv4 IS-IS and IPv6 IS-IS).

By default, IS-IS performs consistency checks on hello packets. If a hello packet does not have the same configured network protocols, IS-IS rejects the packet. For example, a hello packet from a device running IPv4 and IPv6 IS-IS will be rejected by a device running either IPv4 IS-IS only or IPv6 IS-IS only, and the two devices will not become adjacent.

You can configure two devices running different sets of network protocols to form an adjacency.