[ntp:questions] ntp ports

Steve Kostecke kostecke at ntp.org
Mon Nov 10 03:03:17 UTC 2008

On 2008-11-10, Kevin Oberman <oberman at es.net> wrote:

> Melanie Pfefer wrote:
>> What ports need to be opened if my ntp servers are inside a firewall?
> 123/udp

ntpd communicates with other ntpds via port 123/UDP (as both the source
and destination port).

If you are using a statefull firewall ( or are behind NAT) and do not
need to make your ntpd pulically accessible you should not have to do
anything to allow ntpd to work.

If your firewall is not "statefull", or you wish to make your ntpd
publically accesible, you need to allow both incoming and outgoing
connections via port 123/udp.

Steve Kostecke <kostecke at ntp.org>
NTP Public Services Project - http://support.ntp.org/

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