Red Hat Knowledgebase

The line speed and duplex setting must be set at the same time auto-negotiation is disabled on Intel Gigabit network adapters.

When using ethtool to disable auto-negotiation for NICs that use the e1000 module, you must also set the line speed and duplex settings at the same time. For example, the command ethtool -s eth0 autoneg off disables auto-negotiation, but this is only temporary. The driver will automatically re-enable auto-negotiation if the line speed and duplex settings are not specified in the command.

To disable auto-negotiation with ethtool on a NIC using the e1000 module, perform the following steps:

1. Bring up a command prompt.

2. As root, type the following command:

    ethtool -s ethx autoneg off speed 1000 duplex full

   Where ethX is the name for your ethernet device. This will disable autonegotiation on the adapter and set the line speed to 1GB full duplex.

For more information about the ethtool command, consult the manual page by typing man ethtool at the command prompt.

Note: This will not set the speed for the NIC card permanently. There are additional articles in the Knowledgebase that can assist with making these changes permanent.