eth0 (Realtek 8139) suddenly not working

[Peter Thomassen <info@peter-thomassen.de>]

Hi,

I'm still introducing a friend of mine to Linux by phone.

Yesterday and the days before, his Realtek 8139 NCI worked out of the box
using DHCP. Today, no IP is received over DHCP; instead, the boot script
does several tries after different intervals and finally gives up.

I googled around and found a hint that the Firewire interface can occupy
eth0, and indeed, eth1 was present (which I assumed to be the NIC), but
replacing eth0 by eth1 in /etc/network/interfaces didn't work. Also undoing
that change, blacklisting eth1394 in /etc/modules.d/blacklist and rebooting
didn't solve it.

After the reboot, I noticed that 8139too wasn't loaded, so we modprobe'd it;
then ifdown eth0, ifup eth0. No success.

Maybe it's useful to know that dmesg says that eth0 is a Realtek 8139. I
don't know what to do -- do you?

Thanks,
Peter