The Problem
In an office environment with a damaged Ethernet cable, your network adapter may attempt to negotiate a gigabit (1000 Mb) connection and fail. The cable might have degraded to only support 100 Mb capacity, but the auto-negotiation process does not fall back gracefully, leaving you without network access entirely.
Solution
Manually configure the network adapter to operate at 100 Mb speed:
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sudo ethtool -s eth0 speed 100 duplex full
Replace eth0 with your actual network interface name. You can find your interface name using ip link or ifconfig.
Making the Change Persistent
The ethtool command above is temporary and will reset after a system reboot. To make the setting persistent, add the command to a startup script or configure it through your network manager.
For systems using NetworkManager, you can create a dispatcher script in /etc/NetworkManager/dispatcher.d/ that runs the ethtool command when the interface comes up.
Verification
Verify the link speed after applying the change:
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sudo ethtool eth0
Look for the “Speed” line in the output to confirm it shows 100Mb/s.