LKBEN11688: How to list all network interfaces on linux.


Symptom

You have multiple network cards in your server and need some information about these.

Cause

e.g. Which network interface is currently active.

Solution

To list all your network interfaces you can use the ip command.

ip link show

The command will list local loopback, all the interfaces and also the virtual bridges.

lo = Loopback interface

eth0 = normal network card

wlan0 = a wireless network interface

ppp0 = point to point protocal

virbr0 = virtual bridge

On some servers you will not find the notation of eth0, eth1 etc. They will have names like enp2s0f0, enp2s0f1, enp6s0f0, enp6s0f1, ...

Here an example output:

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: enp2s0f0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc mq state DOWN mode DEFAULT group default qlen 1000
    link/ether 00:25:90:9a:3b:dc brd ff:ff:ff:ff:ff:ff
3: enp2s0f1: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc mq state DOWN mode DEFAULT group default qlen 1000
    link/ether 00:25:90:9a:3b:dd brd ff:ff:ff:ff:ff:ff
4: enp6s0f0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc mq state DOWN mode DEFAULT group default qlen 1000
    link/ether 28:80:23:df:b3:50 brd ff:ff:ff:ff:ff:ff
5: enp6s0f1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP mode DEFAULT group default qlen 1000
    link/ether 28:80:23:df:b3:54 brd ff:ff:ff:ff:ff:ff
6: virbr0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN mode DEFAULT group default qlen 1000
    link/ether 52:54:00:d0:7f:1d brd ff:ff:ff:ff:ff:ff

Another possibility is to use the nmcli command:

nmcli device status

DEVICE    TYPE      STATE                   CONNECTION         
enp6s0f1  ethernet  connected               Wired connection 4 
virbr0    bridge    connected (externally)  virbr0             
enp2s0f0  ethernet  unavailable             --                 
enp2s0f1  ethernet  unavailable             --                 
enp6s0f0  ethernet  unavailable             --                 
lo        loopback  unmanaged               --         

nmcli connection show

DEVICE    TYPE      STATE                   CONNECTION         
enp6s0f1  ethernet  connected               Wired connection 4 
virbr0    bridge    connected (externally)  virbr0             
enp2s0f0  ethernet  unavailable             --                 
enp2s0f1  ethernet  unavailable             --                 
enp6s0f0  ethernet  unavailable             --                 
lo        loopback  unmanaged               --         

This will give you a nice overview of your network devices and if they are active or not.

 

Yet another interesting command is tcpdump:

tcpdump --list-interfaces

1.enp6s0f1 [Up, Running, Connected]
2.any (Pseudo-device that captures on all interfaces) [Up, Running]
3.lo [Up, Running, Loopback]
4.enp2s0f0 [Up, Disconnected]
5.enp2s0f1 [Up, Disconnected]
6.enp6s0f0 [Up, Disconnected]
7.virbr0 [Up, Disconnected]
8.bluetooth-monitor (Bluetooth Linux Monitor) [Wireless]
9.nflog (Linux netfilter log (NFLOG) interface) [none]
10.nfqueue (Linux netfilter queue (NFQUEUE) interface) [none]
11.dbus-system (D-Bus system bus) [none]
12.dbus-session (D-Bus session bus) [none]

 

Disclaimer:

The information provided in this document is intended for your information only. Lubby makes no claims to the validity of this information. Use of this information is at own risk!

About the Author

Author: Wim Peeters - Keskon GmbH & Co. KG

Wim Peeters is electronics engineer with an additional master in IT and over 30 years of experience, including time spent in support, development, consulting, training and database administration. Wim has worked with SQL Server since version 6.5. He has developed in C/C++, Java and C# on Windows and Linux. He writes knowledge base articles to solve IT problems and publishes them on the Lubby Knowledge Platform.

Latest update: 20/11/2023