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How can I view and modify the link speed of an ethernet port in Linux?

Usually, the ethtool is your friend in these issues. Use it to view and manipulate the port-settings (speed, duplex, auto-negotiation, etc.) of any ethernet port. You may notice that in the "Port:" information it displays MII. If it displays MII, you may need to use the mii-tool to change the settings of that port, since ethtool might not be compatible.

Update: This is exactly how I fixed a LAN connection once. I had an Ethernet card that was misbehaving, and once I turned off auto-negotiation and set the speed to be 100Base-T, it worked fine. For future reference, I used the command:

/sbin/ethtool -s eth1 autoneg off speed 100
Last updated on 2009-06-08 22:52:56 -0800, by Shalom Craimer

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