How to Change Interface Speed and Duplex on an Ubuntu Linux Server

How to Change Interface Speed and Duplex on an Ubuntu Linux Server

CHUONG K. NGUYEN – BSc., MCSEx2, MCSAx2, MCP, MCTS, MCITP, CCNA

First, you need to list your interface by typing the command:

ifconfig

Assume that the interface in interest is em1, perform a speed/duplex lookup:

ethtool em1

Now set the speed and duplex, remember to turn off autonegotiation

ethtool -s em1 speed 10 duplex full autoneg off

Validate the change by querying the speed/duplex again

ethtool em1

That change will be lost when the server is restarted. If you want this change to be permanent, edit the file /etc/rc.local

cd /etc

vi rc.local

Enter these two lines:

ethtool -s em1 speed 10 duplex full autoneg off

exit 0

Reboot the system and check the speed and duplex again to ensure that the settings are intact.

Ethtool em1

That’s it.