Aruba OS Switch - Switch Not Sending NTP Request Once Failed

By esupport posted Aug 27, 2020 04:19 PM

  

Requirement:

Test Switch - Aruba 5406R 44GT PoE+ and 4-port SFP+ (No PSU) v3 zl2 Switch.

Firmware - All versions.

Issue:
Once NTP servers are configured on the switch, the switch goes ahead and sends ntp request packets to the configured servers.

If one of the servers shows inactive due to the dns resolution failed, there is no packet sent again to check the status.

 

IN076-IT-Jon95dot12# show ntp servers

NTP Server Information

Server Name Resolved Address Server Status
-------------------- -------------------- ---------------------------------
ntp.indiana.edu Failed: DNS resolution failed
ntp.iupui.edu 134.68.1.2 Success: NTP server active
ntp.iu.edu 134.68.220.9 Success: NTP server active

 



Solution:

It is the expected behavior as explained below :

As per our system design, NTP will try to resolve the server-name for maximum of 5 iterations and will not try to resolve further.

  • When NTP server details are configured using ‘server-name’ option, it will simply postpone the NTP protocol update, until DNS resolve complete.
  • 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 failed to resolve, will update the ‘show ntp servers’ output with each server name and the corresponding resolution status and will not retry for resolving the failed entries further.
  • But currently, If the user provides the same server name again, will try resolving again, without incrementing the total NTP server count. (We will re-try only if the server name was not resolved initially (i.e., if the resolve status is other than “Success: NTP server active”). 
  • If it was resolved (i.e., if the resolve status says “Success: NTP server active”) during config, will ignore resolving it again, but the optional parameters for the “ntp server-name …” command if modified are updated. And the “NTP poll process” is now done with these updated parameters.
  • During reboot, will try resolving all the server names entries for max 5 times, in every 30 sec. Incase if any of the entry got resolved during these attempt, will stop retrying it further.

 



Configuration:

timesync ntp
no sntp
ntp unicast
ntp server 129.79.5.100 iburst
ntp server-name "ntp.indiana.edu" iburst
ntp server-name "ntp.iupui.edu" iburst
ntp server-name "ntp.iu.edu" iburst
ntp enable
 



Verification

It is an expected behavior tested and confirmed by lab team.

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