Linux LAN card: Find out full duplex / half speed or mode

To find out the duplex mode and speed of a network interface on a Linux machine, you can use the ethtool command. This command can be used to display and modify the Ethernet device settings.

To display the current duplex mode and speed of an Ethernet interface, you can use the following command:

ethtool INTERFACE

Replace INTERFACE with the name of the interface you want to check (e.g., eth0). This will output information about the interface, including the duplex mode and speed.

For example, the output might look like this:

Settings for eth0:
        Supported ports: [ TP ]
        Supported link modes:   10baseT/Half 10baseT/Full
                                100baseT/Half 100baseT/Full
                                1000baseT/Half 1000baseT/Full
        Supported pause frame use: No
        Supports auto-negotiation: Yes
        Advertised link modes:  10baseT/Half 10baseT/Full
                                100baseT/Half 100baseT/Full
                                1000baseT/Half 1000baseT/Full
        Advertised pause frame use: No
        Advertised auto-negotiation: Yes
        Speed: 1000Mb/s
        Duplex: Full
        Port: Twisted Pair
        PHYAD: 1
        Transceiver: internal
        Auto-negotiation: on
        MDI-X: on (auto)
        Current message level: 0x00000007 (7)
        drv probe ifdown ifup
        Link detected: yes

In this example, the interface is operating at a speed of 1000Mb/s (1 Gb/s) in full duplex mode.