Я думаю вы понимаете вывод следующей команды и что она показывает:
diamond@server:~$ ip link list
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: eth0: <BROADCAST,MULTICAST,PROMISC,UP,LOWER_UP> mtu 1500 qdisc htb master br0 state UP mode DEFAULT group default qlen 1000
link/ether 00:21:85:c0:86:8c brd ff:ff:ff:ff:ff:ff
3: wlan0: <BROADCAST,MULTICAST,PROMISC,UP,LOWER_UP> mtu 1500 qdisc mq master br0 state UP mode DEFAULT group default qlen 1000
link/ether a0:f3:c1:ff:e7:25 brd ff:ff:ff:ff:ff:ff
4: br0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT group default
link/ether 00:21:85:c0:86:8c brd ff:ff:ff:ff:ff:ff
9: ppp0: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP> mtu 1492 qdisc pfifo_fast state UNKNOWN mode DEFAULT group default qlen 3
link/ppp