[ntp:questions] NTP client syncs successfully with NTP server within local network but not with the NTP pool servers

Arpith Nayak arpithnayak at gmail.com
Wed Jan 9 05:41:47 UTC 2013


I am using ntp 4.2.6p5 on linux.

I setup an NTP server on a machine in another subnet and tried to sync
my machine with the server and it works well. But when I try to use
the pool.ntp.org servers (I tried 0.pool.ntp.org, 1.pool.ntp.org, etc.
and just pool.ntp.org servers), it does not sync.

nslookup on pool.ntp.org as well as 0.pool.ntp.org gives proper DNS
resolution and ping works on the IPs returned by nslookup as well.

Output of iptables grepped for UDP is as follows:

[Thu Feb 10 12:39:14 root at root-ubuntu:~]# iptables -L -n -v | grep udp

92 13001 ACCEPT    udp -- *    *     0.0.0.0/0          0.0.0.0/0
   state RELATED,ESTABLISHED
0     0 ACCEPT     udp -- *    *     0.0.0.0/0          0.0.0.0/0
   udp dpt:123
0     0 ACCEPT     udp -- *    *     0.0.0.0/0          0.0.0.0/0
   udp dpt:161
0     0 ACCEPT     udp -- *    *     0.0.0.0/0          0.0.0.0/0
   udp dpt:443
0     0 ACCEPT     udp -- *    *     0.0.0.0/0          0.0.0.0/0
   udp dpt:623
0     0 ACCEPT     udp -- *    *     0.0.0.0/0          0.0.0.0/0
   udp dpt:389
0     0 ACCEPT     udp -- *    *     0.0.0.0/0          0.0.0.0/0
   udp dpt:636
0     0 ACCEPT     udp -- *    *     0.0.0.0/0          0.0.0.0/0
   udp dpt:3268
0     0 ACCEPT     udp -- *    *     0.0.0.0/0          0.0.0.0/0
   udp dpt:3269

Output of the netstat command is as follows:

[Thu Feb 10 12:35:51 root at root-ubuntu:~]# netstat -a | grep udp

udp        0      0 localhost:9473                 0.0.0.0:*
udp        0      0 0.0.0.0:asf-rmcp               0.0.0.0:*
udp        0      0 173.39.22.123:ntp              0.0.0.0:*
udp        0      0 localhost:ntp                  0.0.0.0:*
udp        0      0 0.0.0.0:ntp                    0.0.0.0:*
udp        0      0 all-systems.mcast.net:23000    0.0.0.0:*
udp        0      0 ::1:ntp                        ::%628620:*
udp        0      0 fe80::222:bdff:feea:9f1f:ntp   ::%628620:*
udp        0      0 fe80::222:bdff:feea:9f20:ntp   ::%628620:*
udp        0      0 :::ntp                         ::%628620:*

I am unable to figure out why the sync problem is happening only with
the pool servers and not the local server. The UDP ports in my system
is up. The servers are up. Time however does not sync (It is still
displaying Feb 10.)

Adding my .conf file:

driftfile /tmp/ntp.drift/
server 0.pool.ntp.org
server 1.pool.ntp.org
server 2.pool.ntp.org
server 3.pool.ntp.org

Adding ntpq -p data:

[Thu Feb 10 12:55:51 root at root-ubuntu:~]# ntpq -p 0.pool.ntp.org

     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
*64.147.116.229  .ACTS.           1 u  151 1024  377    2.439   -0.632   0.052
+131.107.13.100  .ACTS.           1 u  879 1024  377   27.853    1.041   0.539
-time.nrc.ca     132.246.11.231   2 u  989 1024  377   86.821   -4.132   8.778
-time1.chu.nrc.c 209.87.233.52    2 u   53 1024  377  109.221    3.153   9.377
+dense.utcc.utor 128.100.200.166  2 u   88 1024  377   64.115   -1.841   0.454
-dns4.utoronto.c 128.100.103.253  2 u  167 1024  377   65.252  -43.422  56.093


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