You'll see an entry like;
Jan 12 15:24:14 kt3 kernel: 8139too Fast Ethernet driver 0.9.26
Jan 12 15:24:14 kt3 kernel: eth0: RealTek RTL8139 Fast Ethernet at 0xd081af00, 00:40:95:30:48:4a, IRQ 18
Jan 12 15:24:14 kt3 kernel: eth0: Identified 8139 chip type 'RTL-8139C'
If you don't see an entry referring eth0 then you will have to find out what kind of ethernet card you are using and install the relevant driver. If you have the standard Woody dist then from a consol do modconf as root (su from user) and go down the list and look for the relevant section (drivers network interface cards)