[networking] Computer can't see the outside world any more

[Gareth Adams <gareth.adams@gmail.com>]

Hi all,

I have a debian server running as a web server on a company network.
The computer has previously been set up as visible to the outside
world, and everything was fine until yesterday.

I noticed yesterday that our home page was showing an error saying it
couldn't connect to an external database it pulls some content from.
The external site was working fine, so I restarted apache (no
diffference) and then restarted the computer. After restart, the
computer failed to pick up an IP address from the DHCP server,
/etc/networking/interfaces looks like

  # The loopback network interface
  auto lo
  iface lo inet loopback

  # The primary network interface
  auto eth0
  iface eth0 inet dhcp

Now the strange thing is that, from logging into the server, I can
ping any local address except for the DHCP server and the default
gateway. I can't ping any global addresses, but this is obviously a
symptom of not being able to reach the gateway. Another machine
plugged into the same hub as the web server has no problem reaching
any address, local or global.

The guys up in IT say nothing has changed in their settings at all.
There haven't been any network related changes to the server in quite
a while.

Where do people think I should start looking? No one here has any idea.

Thanks,
Gareth Adams