Setting Full Duplex mode Ethernet Interface

You can check what mode is enabled before:

# ethtool eth1

to change:

# nano /etc/sysconfig/network-scripts/ifcfg-eth1
ETHTOOL_OPTS="speed 1000 duplex full autoneg off"

Restart Interface:

# ifdown eth1 && ifup eth1

Confirm:

# tail -30 /var/log/messages
# ethtool eth1