This document describes how Hashed Message Authentication Mode (HMAC) in conjunction with the SHA-256, SHA-384, and SHA-512 algorithms can be used for authenticating Bidirectional Forwarding Detection (BFD). It uses the Generic Cryptographic Authentication and Generic Meticulous Cryptographic Authentication sections to carry the authentication data. This updates, but does not supercede, the cryptographic authentication mechanism specified in RFC 5880.