[ntp:questions] Assistance debugging "no servers reachable" errors

Andrew J. Caines A.J.Caines at halplant.com
Tue Dec 18 18:11:59 UTC 2012


I'm looking for guidance on how to diagnose this problem.

Running ntp-4.2.2p1-7 on RHEL 5 host - one of several substantially
similar systems but the only one with this issue - getting "no servers
reachable" errors at roughly the same time each day *only when using auth*.

When there is no auth, there are no ntpd messages logged. When there is
auth, there are multiple instances of "synchronized to" messages, "no
servers reachable" then "synchronized to" followed by a huge "time reset".

Though this issue is clearly related to the host and/or environment I
have yet to find anything relating to the times ntpd loses the server(s).

I have tried two different sets of NTP servers with the same result.


ntp.conf:

server ntp1.example.com iburst key 5
server ntp2.example.com iburst key 5
server ntp3.example.com iburst key 5
restrict -4 default kod notrap nomodify nopeer noquery notrust
restrict -6 default kod notrap nomodify nopeer noquery notrust
keys /etc/ntp.keys
trustedkey 5
requestkey 5

Example log messages for one day, trimmed:

00:36:57 synchronized to 192.168.16.252, stratum 2
02:19:20 synchronized to 192.168.16.251, stratum 2
04:06:22 synchronized to 192.168.16.250, stratum 2
04:07:27 no servers reachable
04:35:51 synchronized to 192.168.16.252, stratum 2
04:40:42 time reset +12.761870 s
04:41:01 synchronized to 192.168.16.250, stratum 2
04:45:11 synchronized to 192.168.16.251, stratum 2
05:05:12 synchronized to 192.168.16.252, stratum 2
05:11:34 synchronized to 192.168.16.251, stratum 2
05:24:25 synchronized to 192.168.16.252, stratum 2
05:39:23 synchronized to 192.168.16.251, stratum 2
05:55:38 synchronized to 192.168.16.252, stratum 2
06:39:13 synchronized to 192.168.16.250, stratum 2
12:11:27 synchronized to 192.168.16.252, stratum 2
13:11:56 synchronized to 192.168.16.250, stratum 2
15:45:32 synchronized to 192.168.16.251, stratum 2
21:27:16 no servers reachable
21:44:10 synchronized to 192.168.16.250, stratum 2
21:52:04 no servers reachable
22:01:24 synchronized to 192.168.16.251, stratum 2
22:01:35 time reset +10.876135 s
22:01:52 synchronized to 192.168.16.252, stratum 2
22:05:35 synchronized to 192.168.16.250, stratum 2
22:13:03 synchronized to 192.168.16.251, stratum 2
22:21:27 synchronized to 192.168.16.250, stratum 2
22:39:49 synchronized to 192.168.16.252, stratum 2
22:52:38 synchronized to 192.168.16.250, stratum 2

More details and answers available on request.

-- 
-Andrew J. Caines-   Unix Systems Engineer   A.J.Caines at halplant.com
FreeBSD/Linux/Solaris, Web/Mail/Proxy/...   http://halplant.com:2001/
  "Machines take me by surprise with great frequency" - Alan Turing


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