[ntp:questions] Re: ntp server behind ADSL alcatel speedtouch 510 firewall not responding.

Ronan Flood ronan at noc.ulcc.ac.uk
Tue Dec 21 11:27:45 UTC 2004

Remko Bolt <marem at concepts.nl> wrote:

> I opened up ports udp/123 and tcp/123 on the alcatel and forward them to
> the ntp-server. I have similar setup's for http and ssh which work fine.
> Problem: The ntp-server is not responding to queries from the outside
> world. It is located at ntp.cluebox.org have a look.
> If I telnet to :80 I get a http welcome etc. This is not so with ntp.

NTP doesn't use TCP, so you can't telnet to port 123.
You can remove tcp/123 from your firewall permissions.

> Is there an easy way to check if a server is accepting connections?

If you have shell access to an external host with the NTP software
installed, try

  ntpdate -q ntp.cluebox.org.
  ntpq -p ntp.cluebox.org.

and see what you get.

> Can anybody confirm that it `should' work this way with the ports set up?
> Any other thoughts?

Depends on what is in your ntp.conf, as Harlan said.

                      Ronan Flood <R.Flood at noc.ulcc.ac.uk>
                        working for but not speaking for
             Network Services, University of London Computer Centre
     (which means: don't bother ULCC if I've said something you don't like)

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