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I've configured ntpd on a CentOs install with a simple /etc/ntp.conf with only 3 lines:

server 0.pool.ntp.org
server 1.pool.ntp.org
server 2.pool.ntp.org
server 192.168.1.1

Unfortunately, no matter what host I run against I cannot get ntpdate to properly sync with an external server. Here is the debug output I get when I run it:

[root@myhost superuser]# ntpdate -d pool.ntp.org
 3 May 12:23:31 ntpdate[3912]: ntpdate 4.2.4p8@1.1612-o Fri Feb 22 11:23:28 UTC 2013 (1)
Looking for host pool.ntp.org and service ntp
host found : 173.44.32.10
transmit(173.44.32.10)
transmit(69.41.163.31)
transmit(18.85.44.118)
transmit(65.182.144.36)
transmit(173.44.32.10)
transmit(69.41.163.31)
transmit(18.85.44.118)
transmit(65.182.144.36)
transmit(173.44.32.10)
transmit(69.41.163.31)
transmit(18.85.44.118)
transmit(65.182.144.36)
transmit(173.44.32.10)
transmit(69.41.163.31)
transmit(18.85.44.118)
transmit(65.182.144.36)
transmit(173.44.32.10)
transmit(69.41.163.31)
transmit(18.85.44.118)
transmit(65.182.144.36)
173.44.32.10: Server dropped: no data
69.41.163.31: Server dropped: no data
18.85.44.118: Server dropped: no data
65.182.144.36: Server dropped: no data
server 173.44.32.10, port 123
stratum 0, precision 0, leap 00, trust 000
refid [173.44.32.10], 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:  d52e6306.7c9cb981  Fri, May  3 2013 12:23:34.486
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 69.41.163.31, port 123
stratum 0, precision 0, leap 00, trust 000
refid [69.41.163.31], 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:  d52e6306.afcfee21  Fri, May  3 2013 12:23:34.686
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 18.85.44.118, port 123
stratum 0, precision 0, leap 00, trust 000
refid [18.85.44.118], 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:  d52e6306.e3031a51  Fri, May  3 2013 12:23:34.886
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 65.182.144.36, port 123
stratum 0, precision 0, leap 00, trust 000
refid [65.182.144.36], 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:  d52e6307.16364db7  Fri, May  3 2013 12:23:35.086
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

 3 May 12:23:36 ntpdate[3912]: no server suitable for synchronization found
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1 Answer

up vote 3 down vote accepted

You need to configure your firewall to allow UDP replies on port 123.

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Ah yes. Iptables was setup correctly but I forgot the corporate firewall wouldn't be as forgiving. Thanks! –  nomizzz May 6 '13 at 14:50
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