O comando ip link show
é provavelmente o que você deseja. Ele exibirá o índice na frente das informações da interface. Exemplo abaixo de um sistema com NICs ligados.
# ip link show
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: eth1: <BROADCAST,MULTICAST,SLAVE,UP,LOWER_UP> mtu 9214 qdisc mq master bond0 portid 000f53000000 state UP mode DEFAULT qlen 1000
link/ether 00:0f:53:00:00:00 brd ff:ff:ff:ff:ff:ff
3: eth0: <BROADCAST,MULTICAST,SLAVE,UP,LOWER_UP> mtu 9214 qdisc mq master bond0 portid 000f53000001 state UP mode DEFAULT qlen 1000
link/ether 00:0f:53:00:00:00 brd ff:ff:ff:ff:ff:ff
4: bond0: <BROADCAST,MULTICAST,MASTER,UP,LOWER_UP> mtu 9214 qdisc noqueue state UP mode DEFAULT qlen 1000
link/ether 00:0f:53:00:00:00 brd ff:ff:ff:ff:ff:ff