Ethtool

ethtool allows you to check if a network cable is correctly plugged into an ethernet port:

# ethtool eth0
Settings for eth0:
       Supported ports: [ MII ]
       Supported link modes:   10baseT/Half 10baseT/Full
                               100baseT/Half 100baseT/Full
                               1000baseT/Half 1000baseT/Full
       Supports auto-negotiation: Yes
       Advertised link modes:  10baseT/Half 10baseT/Full
                               100baseT/Half 100baseT/Full
                               1000baseT/Half 1000baseT/Full
       Advertised auto-negotiation: Yes
       Speed: 1000Mb/s
       Duplex: Full
       Port: Twisted Pair
       PHYAD: 1
       Transceiver: internal
       Auto-negotiation: on
       Supports Wake-on: g
       Wake-on: d
       Current message level: 0x000000ff (255)
       Link detected: yes

This shows you that a physical connection to the network port eth0 has been established. A basic connection to the network switch or computer on the other end of the cable could be established.

See also

• ethtool's man page