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Changing the speed and duplex of Ethernet

This article shows how to set and change the speed and duplexing of an Ethernet device. You can see more examples at “http://www.cyberciti.biz/faq/linux-change-the-speed-and-duplex-settings-of-an-ethernet-card/”.

View the current settings:

mii-tool

The output will be something similar to the following. Notice only physical network devices are listed.

eth0: negotiated 1000baseT-FD flow-control, link ok
eth1: negotiated 100baseTx-FD, link ok
eth2: negotiated 1000baseT-FD flow-control, link ok

You can set the speed and duplexing with the following example commands:

ethtool -s eth0 speed 10 duplex full
ethtool -s eth0 speed 100 duplex full
ethtool -s eth0 speed 1000 duplex full

The first of the above being 10MB/s and the second being 100MB’s. The third is Gigabit.

Note that virtual network devices such as “eth0:1” go by the physical device they’re associated with. So to change the settings for “eth0:1” you’d specify “eth0”.

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