BFD support for IS-IS (for both IPv4 and IPv6 IS-IS neighbors) can be configured so that IS-IS is a registered protocol with BFD.
BFD support for the Intermediate System to Intermediate System (IS-IS) protocol can be configured globally or for specific interfaces.
Note
You cannot configure BFD for an IS-IS session when one side of the IS-IS adjacency uses only IPv4 and the other side uses only IPv6.