On Fri, 1 Jul 2011 23:01:35 +0100, Chris G wrote:

Quite, but how do I diagnose it?

You might find you can see the point you can't get past by using mtr (http://www.bitwizard.nl/mtr/) to watch the points along the route that are working - basically, its a traceroute that dynamically updates to show you where latencies may exist along your route.

In my experience, some devices have issues when accessing a public-side IP which they NAT internally from an internal machine which is itself being NAT'd onto its external side, I have found having an internal IP for the server you are accessing in your private-side DNS servers (or if you can't do that, as a last resort, in your hosts file) is sometimes the only way to resolve the issue where NAT implementations are broken in this way.

HTH,

Jim