Wouldn't hurt to reveal your Linux version.
In Slackware you'd issue:
Code:
mingdao@silas:~$ /sbin/ifconfig
eth0 Link encap:Ethernet HWaddr 00:11:2F:E0:B7:65
inet addr:192.168.1.31 Bcast:192.168.1.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:3168 errors:0 dropped:0 overruns:0 frame:0
TX packets:3026 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:2780574 (2.6 MiB) TX bytes:551271 (538.3 KiB)
Interrupt:19 Memory:fdd00000-0
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:433 errors:0 dropped:0 overruns:0 frame:0
TX packets:433 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:45543 (44.4 KiB) TX bytes:45543 (44.4 KiB)
tap0 Link encap:Ethernet HWaddr 06:27:4B:DC:2F:09
inet addr:10.111.111.254 Bcast:10.111.111.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:1 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:500
RX bytes:53 (53.0 b) TX bytes:0 (0.0 b)
In my motherboard's BIOS the onboard ethernet can be disabled, making eth0 (in my case) disappear.