Trouble with NTPD on client-side

by audioslave   Last Updated July 26, 2017 10:00 AM

we have a problem with the ntp-client on several linux boxes. First of all, there three ntp servers in our network. On most of our boxes the synchronisation is fine. Since yesterday a handfull linux boxes has issues with synching. The boxes are running Debian 8.7 with ntp 4.2.6.p5+dfsg-7+deb8u2 installed.

It look like this:

% sudo ntpq -pn
 remote           refid          st t when poll reach   delay   offset  jitter
==============================================================================
 10.2.1.161      .INIT.          16 u    -   64    0    0.000    0.000   0.000
 10.2.1.159      .INIT.          16 u    -   64    0    0.000    0.000   0.000
 10.2.2.233      .INIT.          16 u    -   64    0    0.000    0.000   0.000

I understand that the values for delay, offset and jitter are 0 because stratum is 16, so the ntp client refuses to sync with the servers.

What I don't understand is, why stratum is at 16. I talked to the firewall guys, nothing is dropped. So I did a tcpdump, but I can not see anything that would explain this behavior.

The client package is like this:

Network Time Protocol (NTP Version 4, client)
    Flags: 0xe3, Leap Indicator: unknown (clock unsynchronized), Version number: NTP Version 4, Mode: client
    Peer Clock Stratum: unspecified or invalid (0)
    Peer Polling Interval: 6 (64 sec)
    Peer Clock Precision: 0.000000 sec
    Root Delay: 0 seconds
    Root Dispersion: 0 seconds
    Reference ID: (Initialization)
    Reference Timestamp: Jan  1, 1970 00:00:00.000000000 UTC
    Origin Timestamp: Jan  1, 1970 00:00:00.000000000 UTC
    Receive Timestamp: Jan  1, 1970 00:00:00.000000000 UTC
    Transmit Timestamp: Jul 26, 2017 08:20:14.664923929 UTC

And the server package is like this:

Network Time Protocol (NTP Version 4, server)
    Flags: 0x24, Leap Indicator: no warning, Version number: NTP Version 4, Mode: server
    Peer Clock Stratum: secondary reference (3)
    Peer Polling Interval: 6 (64 sec)
    Peer Clock Precision: 0.000000 sec
    Root Delay: 0.0225830078125 seconds
    Root Dispersion: 0.0608673095703125 seconds
    Reference ID: 213.239.239.166
    Reference Timestamp: Jul 26, 2017 08:05:26.414539267 UTC
    Origin Timestamp: Jul 26, 2017 08:20:14.664923929 UTC
    Receive Timestamp: Jul 26, 2017 08:20:14.664904341 UTC
    Transmit Timestamp: Jul 26, 2017 08:20:14.664934357 UTC

The syslog entries don't show any error messages either:

Jul 26 10:55:10 servername systemd[1]: Starting LSB: Start NTP daemon...
Jul 26 10:55:10 servername ntpd[131489]: ntpd [email protected] Fri Jul 22 17:30:51 UTC 2016 (1)
Jul 26 10:55:10 servername ntpd[131490]: proto: precision = 0.101 usec
Jul 26 10:55:10 servername ntpd[131490]: Listen and drop on 0 v4wildcard 0.0.0.0 UDP 123
Jul 26 10:55:10 servername ntp[131479]: Starting NTP server: ntpd.
Jul 26 10:55:10 servername systemd[1]: Started LSB: Start NTP daemon.
Jul 26 10:55:10 servername ntpd[131490]: Listen and drop on 1 v6wildcard :: UDP 123
Jul 26 10:55:10 servername ntpd[131490]: Listen normally on 2 lo 127.0.0.1 UDP 123
Jul 26 10:55:10 servername ntpd[131490]: Listen normally on 3 bond0 10.2.32.121 UDP 123
Jul 26 10:55:10 servername ntpd[131490]: Listen normally on 4 lo ::1 UDP 123
Jul 26 10:55:10 servername ntpd[131490]: Listen normally on 5 bond0 fe80::1618:77ff:fe33:2309 UDP 123
Jul 26 10:55:10 servername ntpd[131490]: peers refreshed
Jul 26 10:55:10 servername ntpd[131490]: Listening on routing socket on fd #22 for interface updates

Running ntpdate on the commandline works fine:

% ntpdate -u 10.2.1.161
26 Jul 11:00:05 ntpdate[132651]: adjust time server 10.2.1.161 offset 0.001240 sec

So maybe I don't see the wood for the trees. Anyway, any help would really be appreciated :)

Tank you guys!

Tags : ntpd


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