FORMAT:

       ethtool ethX

       ethtool -h|--help

       ethtool -a|--show-pause ethX

       ethtool -i|--driver ethX
       ethtool -S|--statistics ethX

  ethtool -s ethX [speed 10|100|1000|2500] [duplex half|full] [port tp|aui|bnc|mii] [autoneg on|off] [advertise N] [phyad N] [xcvr internal|external] [wol p|u|m|b|a|g|s|d...]  [sopass xx:yy:zz:aa:bb:cc] [msglvl N] ethtool -f|--flash ethX FILE [N]

DESCRIPTION
       ethtool is used for querying settings of an ethernet device and changing them. ethX is the name of the ethernet device on which ethtool should operate.

 -a --show-pause
              Queries the specified ethernet device for pause parameter information.It includes information about autonegotiation.

localhost:/home/shanky:>ethtool -a eth0
Pause parameters for eth0:
Autonegotiate:  on
RX:             off
TX:             off

 -i --driver
              Queries the specified ethernet device for associated driver setting.

localhost:/home/shanky:>ethtool -i eth0
driver: bnx2
version: 2.0.4
firmware-version: bc 5.2.2 NCSI 2.0.6
bus-info: 0000:03:00.0

 -s --change
              Allows changing some or all settings of the specified ethernet device.   All  following  options  only apply if -s was specified.

ethtool -s eth0 speed 100 duplex full autoneg off

The above command will change the setting for the first NIC eth0 to operate at a fix non-negotiable speed of 100Mb/s and in full duplex mode

-S     queries the specified ethernet device for NIC- and driver-specific statistics. Eg. speed etc .

speed 10|100|1000|2500
              Set  speed  in  Mb/s.   ethtool  with  just the device name as an argument will show you the supported device speeds.

localhost:>ethtool eth0
Settings for eth0:
        Supported ports: [ TP ]
        Supported link modes:   10baseT/Half 10baseT/Full
        100baseT/Half 100baseT/Full                                  1000baseT/Full
        Supports auto-negotiation: Yes
        Advertised link modes:  10baseT/Half  10baseT/Full
        100baseT/Half 100baseT/Full
        1000baseT/Full
        Advertised auto-negotiation: Yes
        Speed: 1000Mb/s
        Duplex: Full
        Port: Twisted Pair
        PHYAD: 1
        Transceiver: internal
        Auto-negotiation: on
        Supports Wake-on: g
        Wake-on: g
        Link detected: yes
 

  duplex half|full
              Sets full or half duplex mode.

  autoneg on|off
              Specifies whether autonegotiation should be enabled. Autonegotiation is enabled  by  deafult,  but  in some network devices may have trouble with it, so you can disable it if really necessary.