Understanding Hitless Authentication Key Rollover for IS-IS

IS-IS protocol exchanges can be authenticated to guarantee that only trusted routing devices participate in routing. By default, authentication is disabled. The authentication algorithm creates an encoded checksum that is included in the transmitted packet. The receiving routing device uses an authentication key (password) to verify the packet’s checksum.

If you configure authentication for all peers, each peer in that group inherits the group’s authentication.

You can update authentication keys without resetting any IS-IS neighbor sessions. This is referred to as hitless authentication key rollover.

Hitless authentication key rollover uses authentication keychains, which consist of the authentication keys that are being updated. The keychain includes multiple keys. Each key in the keychain has a unique start time. At the next key’s start time, a rollover occurs from the current key to the next key, and the next key becomes the current key.

You can choose the algorithm through which authentication is established. You can configure MD5 or SHA-1 authentication. You associate a keychain and the authentication algorithm with an IS-IS neighboring session. Each key contains an identifier and a secret password.

The sending peer chooses the active key based on the system time and the start times of the keys in the keychain. The receiving peer determines the key with which it authenticates based on the incoming key identifier.

You can configure either RFC 5304-based encoding or RFC 5310-based encoding for the IS-IS protocol transmission encoding format.