Ethtool Examples

Ethtool is the defacto tool for interacting with your network adapters.

ethtool ethn0   (or whichever eth device you want information on)
gives you detailed information about your network adapter.

ethtool -i eth0  Will display the driver settings, driver version,firmware version and bus details

ethtool -a eth0  will show you the auto negotiation details of your adapter.

ethtool -S eth0 will display network statistics IE how many bytes have been sent and how many bytes have been received by the adapter.

And then my favourite

ethtool -p eth0   will physically identify your network card by causing the LED's on the network card to flash on and off.  this is very useful when you have multiple network interfaces and need to know which interface is bound to which eth device on your system.

ethtool -t eth0 offline     will bring the adapter offline to perform diagnostics and testing
ethtool -t eth0 online     will perform testing whilst the adapter is online and available to your system)

provided your Nic supports this feature ethertool will perform diagnostics  on your network adapter