ethtool – your NIC’s best friend
Having your network interface card auto-negotiate the connection speed sometimes causes big troubles in terms of data packet loss. Your best friend in such situations is ethtool which is really easy to use, once you get to know it.
You can simply list your current NIC configuration with the following command (asuming you would like to view your eth0 interface):
ethtool eth0 |
It will list information similar to this:
Settings for eth0: Supported ports: [ TP ] Supported link modes: 10baseT/Half 10baseT/Full 100baseT/Half 100baseT/Full 1000baseT/Full Supports auto-negotiation: Yes Advertised link modes: 10baseT/Half 10baseT/Full 100baseT/Half 100baseT/Full 1000baseT/Full Advertised auto-negotiation: Yes Speed: 100Mb/s Duplex: Full Port: Twisted Pair PHYAD: 2 Transceiver: internal Auto-negotiation: on Supports Wake-on: pumbg Wake-on: g Current message level: 0x00000001 (1) Link detected: yes |
To set the connection speed to 10 Mbps full duplex, you will have to do the following:
ethtool -s eth0 speed 10 duplex full autoneg off |
Note that you have to turn autonegotiation off (with autoneg off at the end of the command), or it will still auto negotiate 100 Mbps/Full Duples.
