Linux Interface eth0 / eth1 speed (full / half duplex) change manually

Linux Interface eth0 / eth1 speed (full / half  duplex) change manually
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yum install ethtool
ethtool eth0
ethtool eth1
or mii-tool eth1

Speed: 100Mb/s or Speed: 1000Mb/s ??? if Speed: 100Mb/s and it is a GIG LAN card, then go to

 vi /etc/sysconfig/network-scripts/ifcfg-eth1

ETHTOOL_OPTS="speed 1000 duplex full autoneg off"
:wq

or,,,,,,,   ethtool -s eth1 speed 1000 duplex full autoneg on


ifdown eth1
ifup eth1


ethtool eth1

seee ....now   Speed: 1000Mb/s