1. List Ethernet Device Properties

When you execute ethtool command with a device name, it displays the information about the ethernet device.

# ethtool eth0
2. Change NIC Parameter Using ethtool Option -s autoneg
You can disable this using autoneg option in the ethtool as shown below.
# ifdown eth0
# ethtool -s eth0 autoneg off

# ethtool eth0
3. Change the Speed of Ethernet Device
Using ethtool you can change the speed of the ethernet device to work with the certain network devices, and the newly assign speed value should be within the limited capacity.
# ethtool -s eth0 speed 100 autoneg off
# ifup eth0
4. Display Ethernet Driver Settings
ethtool -i option displays driver version, firmware version and bus details.
# ethtool -i eth0
5. Display Auto-negotiation, RX and TX of eth0
View the autonegotiation details about the specific ethernet device.
# ethtool -a eth0
6. Display Network Statistics of Specific Ethernet Device
Use ethtool -S option to display the bytes transfered, received, errors, etc,
# ethtool -S eth0
7. Identify Specific Device From Multiple Devices (Blink LED Port of NIC Card)
If you have a machine with four ethernet adapters, and you want to identify the physical port of a particular ethernet card. (For example, eth0).
Use ethtool option -p, which will make the corresponding LED of physical port to blink.
# ethtool -p eth0