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Created: 2022-04-22 | Last update: 2022-04-22

Identify Physical Network Interfaces

The Problem

Servers usually have a number of physical network interfaces. The network interfaces names in linux host usually won't tell you much about the which physical network interface corresponds to the interface name. Therefor, it creates a problem when you want to use a specific network interface for a specific purpose but you don't know which physical network interface corresponds to the interface name.

The Solution

ethtool tool can be used to identify the physical network interface corresponding to a network interface name.

For this method to work, you need a physical accessto host's network cards and the physical network interfaces should have Led indicator lights.

Note

This functionality of ethtool may not be supported by all server or network card hardware.

ethtool usually isn't installed by default on a linux host. You can install it by running the following command (debian example):

apt install ethtool

Find the network interfaces present on the host and run the following command for each network interface:

ip addr

or

ifconfig -a

Now you can use the ethtool command to identify the physical network interface corresponding to the network interface name.

Example for eth0 network interface name:

ethtool --identify eth0

This command will run untill you stop it. When it's running, you should see the LED indicator light blinking (usually orange) on the physical network interface corresponding to the network interface name.

To get information about the hardware capabilities of the network interface:

ethtool eth0

output example:

ethtool enp12s0f4

Settings for enp12s0f4:
    Supported ports: [ FIBRE ]
    Supported link modes:   1000baseT/Full
                            10000baseT/Full
    Supported pause frame use: Symmetric Receive-only
    Supports auto-negotiation: No
    Supported FEC modes: None
    Advertised link modes:  10000baseT/Full
    Advertised pause frame use: Symmetric
    Advertised auto-negotiation: No
    Advertised FEC modes: None
    Link partner advertised link modes:  Not reported
    Link partner advertised pause frame use: Symmetric
    Link partner advertised auto-negotiation: No
    Link partner advertised FEC modes: None
    Speed: 10000Mb/s
    Duplex: Full
    Auto-negotiation: off
    Port: Direct Attach Copper
    PHYAD: 255
    Transceiver: internal
        Current message level: 0x000000ff (255)
                               drv probe link timer ifdown ifup rx_err tx_err
    Link detected: yes

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