On Wed, Sep 15, 2010 at 09:14:29AM +0100, Mark Rogers wrote:
If I were to put a network hub between the ADSL router and the main office switch, presumably I could run something on a PC also connected to that switch which would point me in the direction of the problem?
Yes, it probably would be a good first step, you could just try running something on a pc that isn't on that hub to be honest as if it's a broadcast storm or similar and not internet traffic you may see it immediately.
I'm looking for something fairly simple, that would tell me (eg) which IP address was generating most of the traffic, and perhaps on which ports. Wireshark would probably do what I need but it's not (from what I remember) particularly simple to get simple results from.
Wireshark is very easy to get results from, just it may contain too much data for you. There's a few good video tutorials showing you how to create filters on their site to help you pinpoint the problem.
Adam