How can I tell which Ethernet interfaces are connected and/or active?
Installation
When configuring CDRouter it is often necessary to determine which interface names (i.e. eth0, eth1, eth2, etc.) correspond to which physical Ethernet interfaces in the host system. One easy way to do this is using the ifconfig command (/sbin/ifconfig on Fedora systems):
# /sbin/ifconfig
This command shows the status of all configured network interfaces in the host system. Ethernet interfaces that are up and have a physical layer connection will display the word RUNNING, as shown below for interface eth0. Interfaces that do not have a physical layer connection will not display RUNNING, as shown below for interfaces eth1 and eth2.
To figure out the interface name for a specific physical Ethernet interface, just plug that interface into a live device and unplug all other connections. Then run the ifconfig command look for the RUNNING interface.
eth0 Link encap:Ethernet HWaddr 00:11:11:B7:4F:5D
inet addr:172.16.1.23 Bcast:172.16.1.255 Mask:255.255.255.0
inet6 addr: fe80::211:11ff:feb7:4f5d/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:1318724 errors:0 dropped:0 overruns:0 frame:0
TX packets:1295518 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:306633434 (292.4 MiB) TX bytes:1622064841 (1.5 GiB)
eth1 Link encap:Ethernet HWaddr 00:C0:95:E0:F1:48
inet6 addr: fe80::2c0:95ff:fee0:f148/64 Scope:Link
UP BROADCAST MULTICAST MTU:1500 Metric:1
RX packets:227846 errors:1 dropped:0 overruns:0 frame:0
TX packets:235631 errors:12 dropped:0 overruns:0 carrier:24
collisions:0 txqueuelen:1000
RX bytes:44481929 (42.4 MiB) TX bytes:56332949 (53.7 MiB)
Interrupt:21 Base address:0xf00
eth2 Link encap:Ethernet HWaddr 00:C0:95:E0:F1:49
inet6 addr: fe80::2c0:95ff:fee0:f149/64 Scope:Link
UP BROADCAST MULTICAST MTU:1500 Metric:1
RX packets:391940 errors:1 dropped:0 overruns:0 frame:0
TX packets:340222 errors:11 dropped:0 overruns:0 carrier:22
collisions:0 txqueuelen:1000
RX bytes:71262128 (67.9 MiB) TX bytes:71976392 (68.6 MiB)
Interrupt:22 Base address:0x2f80
