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The problem I'm trying to solve is that NTP won't synchronize:

$ sudo ntpstat
unsynchronised
  time server re-starting
   polling server every 64 s

Edit: Here's some ntpq output:

$ sudo ntpq -c peers
     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
 ntp.eecs.wsu.ed .INIT.          16 u    -   64    0    0.000    0.000   0.000
 71.19.224.242   .INIT.          16 u    -   64    0    0.000    0.000   0.000
 ntp4.vps.net    .INIT.          16 u    -   64    0    0.000    0.000   0.000
 mercury.z0p.org .INIT.          16 u    -   64    0    0.000    0.000   0.000
 li506-17.member .INIT.          16 u    -   64    0    0.000    0.000   0.000
 4.53.160.75     .INIT.          16 u    -   64    0    0.000    0.000   0.000
 ntp1.ResComp.Be .INIT.          16 u    -   64    0    0.000    0.000   0.000

I have the default RHEL6 /etc/ntp.conf configuration. Servers bit:

server 0.rhel.pool.ntp.org
server 1.rhel.pool.ntp.org
server 2.rhel.pool.ntp.org

When I stop ntpd and try to run ntpdate manually, I get a "no server suitable for synchronization found" for all of those servers. Here's ntpdate with debug output:

$ ntpdate -dq 1.rhel.pool.ntp.org
10 May 10:02:42 ntpdate[13320]: ntpdate 4.2.4p8@1.1612-o Thu May 13 14:38:25 UTC 2010 (1)
Looking for host 1.rhel.pool.ntp.org and service ntp
host found : caprica.willglynn.com
transmit(208.88.126.226)
transmit(66.225.61.66)
transmit(149.20.68.17)
transmit(4.53.160.75)
transmit(208.88.126.226)
transmit(66.225.61.66)
transmit(149.20.68.17)
transmit(4.53.160.75)
transmit(208.88.126.226)
transmit(66.225.61.66)
transmit(149.20.68.17)
transmit(4.53.160.75)
transmit(208.88.126.226)
transmit(66.225.61.66)
transmit(149.20.68.17)
transmit(4.53.160.75)
transmit(208.88.126.226)
transmit(66.225.61.66)
transmit(149.20.68.17)
transmit(4.53.160.75)
208.88.126.226: Server dropped: no data
66.225.61.66: Server dropped: no data
149.20.68.17: Server dropped: no data
4.53.160.75: Server dropped: no data
server 208.88.126.226, port 123
stratum 0, precision 0, leap 00, trust 000
refid [208.88.126.226], delay 0.00000, dispersion 64.00000
transmitted 4, in filter 4
reference time:    00000000.00000000  Thu, Feb  7 2036  1:28:16.000
originate timestamp: 00000000.00000000  Thu, Feb  7 2036  1:28:16.000
transmit timestamp:  d5377c86.25dd5f5a  Fri, May 10 2013 10:02:46.147
filter delay:  0.00000  0.00000  0.00000  0.00000
         0.00000  0.00000  0.00000  0.00000
filter offset: 0.000000 0.000000 0.000000 0.000000
         0.000000 0.000000 0.000000 0.000000
delay 0.00000, dispersion 64.00000
offset 0.000000

server 66.225.61.66, port 123
stratum 0, precision 0, leap 00, trust 000
refid [66.225.61.66], delay 0.00000, dispersion 64.00000
transmitted 4, in filter 4
reference time:    00000000.00000000  Thu, Feb  7 2036  1:28:16.000
originate timestamp: 00000000.00000000  Thu, Feb  7 2036  1:28:16.000
transmit timestamp:  d5377c86.591061f7  Fri, May 10 2013 10:02:46.347
filter delay:  0.00000  0.00000  0.00000  0.00000
         0.00000  0.00000  0.00000  0.00000
filter offset: 0.000000 0.000000 0.000000 0.000000
         0.000000 0.000000 0.000000 0.000000
delay 0.00000, dispersion 64.00000
offset 0.000000

server 149.20.68.17, port 123
stratum 0, precision 0, leap 00, trust 000
refid [149.20.68.17], delay 0.00000, dispersion 64.00000
transmitted 4, in filter 4
reference time:    00000000.00000000  Thu, Feb  7 2036  1:28:16.000
originate timestamp: 00000000.00000000  Thu, Feb  7 2036  1:28:16.000
transmit timestamp:  d5377c86.8c427d35  Fri, May 10 2013 10:02:46.547
filter delay:  0.00000  0.00000  0.00000  0.00000
         0.00000  0.00000  0.00000  0.00000
filter offset: 0.000000 0.000000 0.000000 0.000000
         0.000000 0.000000 0.000000 0.000000
delay 0.00000, dispersion 64.00000
offset 0.000000

server 4.53.160.75, port 123
stratum 0, precision 0, leap 00, trust 000
refid [4.53.160.75], delay 0.00000, dispersion 64.00000
transmitted 4, in filter 4
reference time:    00000000.00000000  Thu, Feb  7 2036  1:28:16.000
originate timestamp: 00000000.00000000  Thu, Feb  7 2036  1:28:16.000
transmit timestamp:  d5377c86.bf762a87  Fri, May 10 2013 10:02:46.747
filter delay:  0.00000  0.00000  0.00000  0.00000
         0.00000  0.00000  0.00000  0.00000
filter offset: 0.000000 0.000000 0.000000 0.000000
         0.000000 0.000000 0.000000 0.000000
delay 0.00000, dispersion 64.00000
offset 0.000000

10 May 10:02:47 ntpdate[13320]: no server suitable for synchronization found

I can ping some of the NTP servers the pool directs me to:

$ ping caprica.willglynn.com
PING caprica.willglynn.com (208.88.126.226) 56(84) bytes of data.
64 bytes from caprica.willglynn.com (208.88.126.226): icmp_seq=1 ttl=52 time=60.2 ms
64 bytes from caprica.willglynn.com (208.88.126.226): icmp_seq=2 ttl=52 time=59.6 ms
64 bytes from caprica.willglynn.com (208.88.126.226): icmp_seq=3 ttl=52 time=59.9 ms
64 bytes from caprica.willglynn.com (208.88.126.226): icmp_seq=4 ttl=52 time=59.8 ms

Netstat for port 123:

$ netstat -ano|grep 123
udp        0      0 10.0.116.6:123              0.0.0.0:*                               off (0.00/0/0)
udp        0      0 127.0.0.1:123               0.0.0.0:*                               off (0.00/0/0)
udp        0      0 0.0.0.0:123                 0.0.0.0:*                               off (0.00/0/0)
udp        0      0 :::123                      :::*                                    off (0.00/0/0)

iptables and ip6tables are off, but there is an external firewall that should have port 123 open for UDP.

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2  
Your client is not able to reach the NTP server.. It may be because of many issues.. Is there a firewall that is preventing the access?.. This would be my likely guess... –  vijay rajah May 10 '13 at 14:31
    
"external firewall that should have port 123 open.." to me means you haven't verified and confirmed there are no weird NAT/access rules in place on the external firewall preventing communication. From my point of view, the evidence looks like it points to a firewall/connectivity issue. –  Rex May 10 '13 at 14:49
    
It turned out to be a corporate firewall issue between the zone the server was in and the rest of the internet. I have now been able to run ntpdate manually, and I'm assuming ntpd will start working shortly. –  Leons May 13 '13 at 14:41
1  
can you close this question so people dont waste their time trying to answer open questions? –  dfc Jan 21 at 6:02

1 Answer 1

up vote 1 down vote accepted

Make sure there isn't an external firewall between the machine and the rest of the internet. If there is, request that the people administering the firewall open port 123.

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