ntp.conf

[archangel84]

Hi Guys,

I am having a problem where my server is changing its synchronization with 2 NTP servers every few min.

server:~ # cat /var/log/messages | grep ntpd | tail -4
Oct 7 13:04:30 server ntpd[17699]: synchronized to 10.228.15.2, stratum 3
Oct 7 13:38:30 server ntpd[17699]: synchronized to 10.228.15.3, stratum 3
Oct 7 13:38:39 server ntpd[17699]: synchronized to 10.228.15.2, stratum 3
Oct 7 14:12:40 server ntpd[17699]: synchronized to 10.228.15.3, stratum 3
server:~ #


server:~ # ntpq -p
remote refid st t when poll reach delay offset jitter
================================================== ============================
+10.228.1.15 142.165.20.210 2 u 280 1024 377 4.775 11.031 11.108
+10.228.1.25 .INIT. 16 u 555 1024 376 4.724 -0.128 0.041
*10.228.15.2 10.228.1.25 3 u 565 1024 377 4.894 -0.006 0.030
+10.228.15.3 10.228.1.25 3 u 1022 1024 377 4.902 -0.178 0.051
server:~ #

server:~ # ntpq -p
remote refid st t when poll reach delay offset jitter
================================================== ============================
+10.228.1.15 142.165.20.210 2 u 788 1024 377 4.775 11.031 11.108
10.228.1.25 .INIT. 16 u 1063 1024 374 4.724 -0.128 0.041
+10.228.15.2 10.228.1.25 3 u 47 1024 377 4.867 -0.052 0.046
*10.228.15.3 10.228.1.25 3 u 503 1024 377 4.922 -0.150 0.028
server:~ #

When I checked the ntp.conf file, I see the parameter "prefer" with 2 IPs. Is this the reason this is happening ?


server:~ # cat /etc/ntp.conf

server 10.228.1.15
server 10.228.1.25
server 10.228.15.2 prefer
server 10.228.15.3 prefer
# logconfig =syncstatus + sysevents
# logconfig =all

# statsdir /tmp/ # directory for statistics files
# filegen peerstats file peerstats type day enable
# filegen loopstats file loopstats type day enable
# filegen clockstats file clockstats type day enable

#
# Authentication stuff
#
# keys /etc/ntp.keys # path for keys file
# trustedkey 1 2 3 4 5 6 14 15 # define trusted keys
# requestkey 15 # key (7) for accessing server variables
# controlkey 15 # key (6) for accessing server variables

I've tried to compare other values such as delay, jitter etc but it doesn't make sense. I've checked /var/log/messages for alarms related to interfaces as well but can't see any link going down.

Any help would be highly appreciated.

[archangel84]

Guys,
I guess I've figured out the problem. Basically the stratum value changed for one of the NTP servers and thats why the other NTP server was selected.

Stratum changed from 3 to 4. But the weird thing is that it takes the server a little while to display the changed value. Server synchronizes to the other NTP server immediately but displays the changed stratum value after a while.

server:~ # ntpq -p
remote refid st t when poll reach delay offset jitter
================================================== ============================
+10.228.1.15 142.165.20.210 2 u 1547 1024 376 4.775 11.031 11.108
10.228.1.25 .INIT. 16 u 1822 1024 374 4.724 -0.128 0.041
+10.228.15.2 10.228.1.25 3 u 806 1024 377 4.867 -0.052 0.046
*10.228.15.3 10.228.1.25 3 u 237 1024 377 4.871 0.929 1.080

In the above output of "ntpq -p" display, the stratum value for 10.228.15.2 is still 3 but the server is not synchronized to 10.228.15.3.

server:~ # ntpq -p
remote refid st t when poll reach delay offset jitter
================================================== ============================
+10.228.1.15 142.165.20.210 2 u 44m 1024 374 4.775 11.031 11.108
10.228.1.25 .INIT. 16 u 48m 1024 370 4.724 -0.128 0.041
+10.228.15.2 10.228.15.3 4 u 846 1024 377 4.858 0.315 0.367
*10.228.15.3 10.228.1.25 3 u 278 1024 377 4.913 1.823 0.893

Here you see the changed stratum value.

server:~ # ntpq -p
remote refid st t when poll reach delay offset jitter
================================================== ============================
10.228.1.15 142.165.20.210 2 u 54m 1024 370 4.775 11.031 11.108
10.228.1.25 .INIT. 16 u 59m 1024 360 4.724 -0.128 0.041
+10.228.15.2 10.228.15.3 4 u 458 1024 377 4.955 0.608 0.293
*10.228.15.3 10.228.1.25 3 u 915 1024 377 4.913 1.823 0.893

Please let me know if you guys think any differently.