On 2011-01-14, Chris Albertson <[email protected]> wrote:

> RICCARDO wrote:
>
>> Can I avoid ntpd service doesn't listen to port 123 on this client
>> ?
>
> You don't say why you needs this.

It's usually the old "open ports are bad ports" meme. Or it's the desire
to not accept any unsolicited connections.

> I'm assuming there is a firewall and you do not have the ability to
> re-configure it.

Interesting thought.

> Do you have VPN access through the firewall. The other thing is to
> make an SSH "tunnel" and forward port 123 data via SSH.

Forwarding NTP packets over a VPN or through SSH is a good way to
increase latency and jitter.

> I think with effort you can get NTP to use a different port

Changing the NTP source port is simple if you're able to compile the
source. This gives you security through obscurity at the expense of
breaking ntpq (and ntpdc).

> What about setting up the server for broadcast? Then your client can
> be a broadcast client

The client still has to bind the NTP port on the interface facing the
broadcast server.

> As a last resort you can buy a GPS receiver for $80, use that for a
> reference and ignore the server.

Another interesting thought.

-- 
Steve Kostecke <[email protected]>
NTP Public Services Project - http://support.ntp.org/

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