Finally find some time to fix my NTP setup to sync the clock on all my machine. It's broken for quite sometimes that require manual action during summer time clock change....

On the server side, I need to change the default to allow interaction with other servers (instead of ignore).

restrict default nomodify notrap noquery

Then setup the server to sync with. I found there is a pool of NTP servers all should be using now and my old serever seem ignore me for that reason.

server 0.pool.ntp.org

server 1.pool.ntp.org

server ca.pool.ntp.org

To allow internal machines to sync their time, I setup the server that it allow sync from internal network.

restrict 192.168.2.0 mask 255.255.255.0 nomodify notrap

For testing whether the server's working, ntpq -np is used. (* is good!)

[root@admun root]# ntpq -np

     remote           refid      st t when poll reach   delay   offset  jitter

==============================================================================

+64.81.96.73     216.218.254.202  2 u  657 1024  377  117.579    3.048 127.781

*192.36.143.153  .PPS.            1 u  549 1024  377  119.891  -10.878   3.679

+216.138.199.179 192.168.1.1      4 u  609 1024  377   21.354   -4.961  13.340

The rest are remain the same as default setup.