time synchronisation problem

Unanswered Question
Apr 22nd, 2009

We were using external clock source for some of the systems.Few months back the time synchronising was not proper on these as reported by other teams.So, the systems began to point towards one of the network switches for ntp.Now they are ok with the sync.

Any idea how to check further what could be the problem.


I have this problem too.
0 votes
  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 3.5 (2 ratings)
Anonymous (not verified) Wed, 04/29/2009 - 13:13

User sh clock and show log command on the switch to troubleshoot the time synchronisation issues. And also use this command service timestamps debug datetime msec local.

Leo Laohoo Wed, 04/29/2009 - 16:01

"sh ntp associate" and "sh clock".

If the output of the "sh clock" begins with a ".", your Cisco appliance does not have a valid time source.

If the output of the "sh ntp associate" begins with a "*" it means the Cisco appliance is synchronise while the output that begins with "~" means it's not.

Hope this helps.

suthomas1 Wed, 04/29/2009 - 16:13

these outputs are fine on the device.

How do we check what went wrong with the sync problem between external time source over the network?

The switch as time source is a temporary option.


Leo Laohoo Wed, 04/29/2009 - 17:39

On the contrary, if a host needs NTP/SNTP source, I wouldn't allow it to go through the network to sychronise but instead go to the switch it's currently connected to for time source.

If you want to find out why your appliance is not synchronising with the time source, configure your switch/router to synchronise to it and enable debug.

suthomas1 Wed, 04/29/2009 - 18:03

1.So you mean it always better to have the end nodes synchronise with the network device & the network device inturns points or syncs with the external clock source?

Any specific reasons.

2. switch should be used to test sync with the appliance , which would mean..make the appliance master for testing period for the switch?


Leo Laohoo Wed, 04/29/2009 - 19:26

1. There's nothing wrong with what you are doing. In my humble opinion, instead of having a significant amount of clients going across the network just to synchronise with an NTP source, I'd rather have them go to the nearest Cisco access switch/router. The Cisco access routers/switches then talk to their nearest distribution routers/switches, and so on. I know NTP/SNTP is just a drop in the bucket in regards to network traffic but I want to keep all local traffic local.

2. Just have the client point to your switch as a ntp source would do fine. Try to avoid using the command "ntp master" as this might confuse the appliance looking for synchronising.


This Discussion