Linux - Determine / Find Ethernet Connection Speed

To determine the Ethernet connection speed on a Linux system, you can use the ethtool command.

1. Determine the name of the network interface that you want to check the connection speed for. You can use the ip a command to list all the network interfaces:

ip a

The output will list the names of the network interfaces, along with their status and IP address information.

2. Use the ethtool command to display the connection speed for the network interface:

ethtool INTERFACE

Replace INTERFACE with the name of the network interface.

For example, to check the connection speed for the eth0 interface, you would run:

ethtool eth0

The output will display various information about the network interface, including the connection speed and duplex mode.

Here is an example of the output for a 100 Mbps full duplex connection:

Settings for eth0:
        Supported ports: [ TP ]
        Supported link modes:   10baseT/Half 10baseT/Full
                                100baseT/Half 100baseT/Full
        Supported pause frame use: No
        Supports auto-negotiation: Yes
        Advertised link modes:  10baseT/Half 10baseT/Full
                                100baseT/Half 100baseT/Full
        Advertised pause frame use: No
        Advertised auto-negotiation: Yes
        Link partner advertised link modes:  10baseT/Half 10baseT/Full
                                             100baseT/Half 100baseT/Full
        Link partner advertised pause frame use: No
        Link partner advertised auto-negotiation: Yes
        Speed: 100Mb/s
        Duplex: Full
        Port: Twisted Pair
        PHYAD: 1
        Transceiver: internal
        Auto-negotiation: on
        MDI-X: off (auto)