Symptom

The router will fail to sync and take time from an NTP server (any linux box). available hmac-sha1 and hmac-sha2-256 option in IOS-NTP, are not working if peer is using opensource NTP.

Conditions

The router is configured to authenticate to the server via symmetric key using an algorithm of hmac-sha1 and hmac-sha2-256.

Workaround

Use the MD5 algorithm for authentication or connect to the server without authentication

Further Problem Description