FQDN support for NTP servers

Fully Qualified Domain Name (FQDN) for a NTP server allows for the configuration of server names. Support for handling multiple IP addresses is resolved as part of a DNS resolution. NTP unicast server configuration with the FQDN option can support up to 8 NTP servers including a NTP server configured using an IPv4 address. The user configured host name will be saved in configuration and during NTP protocol updates, the hostname will resolve and the IP address updated to the existing NTP protocol data structure. Actual NTP server request will happen through IP address only.

NTP server configuration should allow sever name (FQDNs) to be configured without breaking backward compatibility.

For more information on configuring NTP servers, refer to the Management and Configuration Guide for your switch.


  • When NTP server details are configured using 'server-name' option, it will postpone the NTP protocol update until DNS resolution is completed or DNS resolution completes.

  • If there is any failure or delay in DNS resolution, it can delay the usage of configured server for further NTP process.

  • If the user provided NTP server names fail to resolve, the show ntp servers output will show each server name and the corresponding resolution status. The NTP server will not retry resolving any failed entries. Retrying the same server name will attempt resolution without incrementing the total NTP server count.


  • NTP server will not support resolving server hostname on every NTP poll sequence.

  • NTP does not check for the directed broadcast IP.