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I have an HPUX NTP Server. It is the server for a dumb client device that has NTP built-in. I can tell the client the server IP and interval but cannot get any logging out.

How do I know if NTP syncronization is taking place.

Ordinarily, I would go to the client and run:

ntpq -p

but in this case the client can't do that. Is it possible to get a list of clients syncronized with my NTP server from the server itself?

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3 Answers 3

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16

tcpdump port 123 ?

ntpdc -c monlist might also work as well, though I don't have a ntp server handy to test.

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    ntpdc -c monlist works properly here under various distribution of the ntp 4.2.4 release.
    – Magellan
    Feb 23, 2012 at 0:33
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    I would add a -n to your ntpdc as well, just to speed things up, if you don't have reverse DNS setup for all your hosts.
    – Zoredache
    Feb 23, 2012 at 0:38
  • @rany Why did you edit this? That was a very poor edit and did not properly contribute to the content.
    – Wesley
    Jan 11, 2017 at 3:56
  • It is worth mentioning that if tcpdump is reporting Client lines but no Server lines, this means the NTP server is not responding. This might be due to a firewall or routing problem.
    – DustWolf
    Jul 7, 2020 at 14:46
  • The monlist command won't work on a well-secured system because of a security vulnerability.
    – Thagomizer
    Aug 15, 2020 at 4:47
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#ntpdc -c monlist

will show exactly what clients are being served by the NTP server. However, I suggest to do ntp service restart prior to listing. This is because, the list will contain old clients as well, including ones which might be listened long back and then removed from the network/decommissioned.

#service ntpd restart 
#ntpdc -c monlist

This will give you exactly the current data.

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  • The monlist command won't work on a well-secured system because of a security vulnerability.
    – Thagomizer
    Aug 15, 2020 at 4:48
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You can check for traffic from the device to be sure synchronizing is attempted (named in the other answers) but the device still has to do something with the answer. Without (remote) logging or some status display you can't say for sure the device is synchronized.

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