Network problem: hard or soft?

[Darren Cook <darrenj@example.com>]

I switched my test server off yesterday to move and dust... it rebooted
okay but it won't let me assign IP addresses to the network card (I
can't ping the router; running ifup -a manually failed). The network
card detected okay in the boot sequence and there are no errors for it.

The connectivity light is on on the router, but off on the network card
on the server. First time I've seen that - they are normally either both
on or both off. When I turning server power off the light goes off on
the router.

Am I looking for a config problem or a new network card? This is the
first time I've rebooted since I added new ip addresses to that card a
month or two back. IIRC I just edited /etc/network/interfaces. (Debian
potato).

Darren