How to Change Duplex on Linux

In Linux a lot of network configurations are controlled through the command line, even though the majority of the operating systems can now be controlled in the graphical user interface. Therefore if you want to change your network card's duplex mode, you have to use the command line. This is useful as it means the process is universal across all Linux distributions, rather than being specific to individual operating system versions.

Instructions

1. Open your Linux Terminal. This process is different for each Linux distribution, although most operating systems have an icon on the desktop for the Terminal. Double-click the "Terminal" icon to open the Linux Terminal if it appears on your desktop. Consult your documentation for assistance on how to open the Linux Terminal if you use a rarer distribution that does not have this feature.

2. Type "dmesg | grep -i duplex" and press "Enter" to display the type of duplex mode in use. In the printed message it will define the type of duplex in use.

3. Type "mii-tool" and press "Enter" to display the duplex mode string. There are four possible options: 100baseTx-FD: 100Mbps full duplex (FD); 100baseTx-HD: 100Mbps half duplex (HD); 10baseT-FD: 10Mbps full duplex (FD) and 10baseT-HD: 10Mbps half duplex (HD).

4. Type "mii-tool -F 100baseTx-FD" and press "Enter" to change the mode to full duplex at full speed. Replace "100baseTx-FD" with one of the tags listed above for another speed.

5. Click the "Close" icon at the top of the Terminal to exit or type "exit" and press "Enter."

References

• NixCraft: Linux LAN card: Find Out Full Duplex/Half Speed or Mode
• Net Admin Tools; Manual of MII-TOOL; David Hinds, et al; April, 2000