[ntp:questions] peers using same server

David L. Mills mills at udel.edu
Mon Nov 1 14:55:38 UTC 2010


Miroslav,

Depends on the synchronization distance. See the online page How NTP Works.

Dave

Miroslav Lichvar wrote:

>I've come across an interesting problem and I'm not sure if this is a
>bug or feature.
>
>When two peers are configured to use the same server as their source
>and the link between one peer and the server goes down, the peer
>doesn't switch to the other peer and will stay unsynchronized.
>
> 1 Jan 01:00:00 ntpd[3468]: ntpd 4.2.7p71 at 1.2297 Mon Oct 25 09:43:53 UTC 2010 (1)
> 1 Jan 01:00:00 ntpd[3468]: proto: precision = 0.101 usec
> 1 Jan 01:00:00 ntpd[3468]: ntp_io: estimated max descriptors: 1024, initial socket boundary: 16
> 1 Jan 01:00:00 ntpd[3468]: Listen and drop on 0 v4wildcard 0.0.0.0 UDP 123
> 1 Jan 01:00:00 ntpd[3468]: Listen normally on 1 lo 127.0.0.1 UDP 123
> 1 Jan 01:00:00 ntpd[3468]: Listen normally on 2 eth0 192.168.123.4 UDP 123
> 1 Jan 01:00:00 ntpd[3468]: 192.168.123.1 8011 81 mobilize assoc 9201
> 1 Jan 01:00:00 ntpd[3468]: 192.168.123.3 8011 81 mobilize assoc 9202
> 1 Jan 01:00:00 ntpd[3468]: 0.0.0.0 c016 06 restart
> 1 Jan 01:00:00 ntpd[3468]: 0.0.0.0 c012 02 freq_set kernel 100.000 PPM
> 1 Jan 01:05:29 ntpd[3468]: 192.168.123.3 8024 84 reachable
> 1 Jan 01:08:44 ntpd[3468]: 192.168.123.3 963a 8a sys_peer
> 1 Jan 01:08:44 ntpd[3468]: 0.0.0.0 c615 05 clock_sync
> 1 Jan 19:11:37 ntpd[3468]: 192.168.123.1 8024 84 reachable
> 1 Jan 19:40:48 ntpd[3468]: 192.168.123.1 963a 8a sys_peer
> 1 Jan 22:03:04 ntpd[3468]: 192.168.123.1 8643 83 unreachable
> 1 Jan 22:07:08 ntpd[3468]: 0.0.0.0 0618 08 no_sys_peer
> 2 Jan 16:07:01 ntpd[3468]: 192.168.123.1 8054 84 reachable
> 2 Jan 16:12:32 ntpd[3468]: 192.168.123.1 966a 8a sys_peer
> 2 Jan 18:58:12 ntpd[3468]: 192.168.123.1 8673 83 unreachable
> 2 Jan 19:00:34 ntpd[3468]: 0.0.0.0 0628 08 no_sys_peer
>
>But when each peer uses a different server, they will switch to the
>other peer quickly when the link goes down.
>
> 1 Jan 01:00:00 ntpd[3635]: ntpd 4.2.7p71 at 1.2297 Mon Oct 25 09:43:53 UTC 2010 (1)
> 1 Jan 01:00:00 ntpd[3635]: proto: precision = 0.101 usec
> 1 Jan 01:00:00 ntpd[3635]: ntp_io: estimated max descriptors: 1024, initial socket boundary: 16
> 1 Jan 01:00:00 ntpd[3635]: Listen and drop on 0 v4wildcard 0.0.0.0 UDP 123
> 1 Jan 01:00:00 ntpd[3635]: Listen normally on 1 lo 127.0.0.1 UDP 123
> 1 Jan 01:00:00 ntpd[3635]: Listen normally on 2 eth0 192.168.123.4 UDP 123
> 1 Jan 01:00:00 ntpd[3635]: 192.168.123.2 8011 81 mobilize assoc 9201
> 1 Jan 01:00:00 ntpd[3635]: 192.168.123.3 8011 81 mobilize assoc 9202
> 1 Jan 01:00:00 ntpd[3635]: 0.0.0.0 c016 06 restart
> 1 Jan 01:00:00 ntpd[3635]: 0.0.0.0 c012 02 freq_set kernel 100.000 PPM
> 1 Jan 01:05:29 ntpd[3635]: 192.168.123.3 8024 84 reachable
> 1 Jan 01:09:54 ntpd[3635]: 192.168.123.3 963a 8a sys_peer
> 1 Jan 01:09:54 ntpd[3635]: 0.0.0.0 c615 05 clock_sync
> 1 Jan 02:49:28 ntpd[3635]: 192.168.123.2 8024 84 reachable
> 1 Jan 03:11:52 ntpd[3635]: 192.168.123.2 963a 8a sys_peer
> 1 Jan 05:40:36 ntpd[3635]: 192.168.123.2 8643 83 unreachable
> 1 Jan 05:48:17 ntpd[3635]: 192.168.123.3 961a 8a sys_peer
> 1 Jan 07:22:11 ntpd[3635]: 192.168.123.2 8054 84 reachable
> 1 Jan 08:01:28 ntpd[3635]: 192.168.123.2 966a 8a sys_peer
> 1 Jan 10:13:37 ntpd[3635]: 192.168.123.2 8673 83 unreachable
> 1 Jan 10:20:08 ntpd[3635]: 192.168.123.3 961a 8a sys_peer
>
>Any explanation for this? I've tried versions 4.2.2, 4.2.4, 4.2.6 and
>the latest dev, the result is always the same.
>
>Thanks,
>
>  
>




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