This is quite short, but I spent many hours trying to figure out how to fix my router. Basically, a Davicom-based ethernet card would appear in System->Administration->Networking but would _never_ get an IP address from the router with dhcp. The cabling was OK, the green lights turned on on the router and on the ethernet card, but still no IP. After lots of frustration, I figured the problem out. To understand it, here's my lspci :
0000:00:0b.0 Ethernet controller: Davicom Semiconductor, Inc. 21x4x DEC-Tulip compatible 10/100 Ethernet (rev 40)
As you can see, it is supposedly tulip-compatible. It isn't _totally_ compatible though. It's compatible enough to be detected and picked up, but not to work. What I had to do was:
sudo rmmod tulip sudo rmmod dmfe sudo modprobe dmfe
The dmfe driver is more compatible than the tulip one, and it worked immediately.