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Chapter 10. Adjusting Network Settings

10.1. Changing Network Adapter Settings

To check the speed and settings of network adapters, use the ethtool command which works now for most network interface cards. To check the adapter settings of eth0 run:
# ethtool eth0
To force a speed change to 1000Mbps, full duplex mode, run:
# ethtool -s eth0 speed 1000 duplex full autoneg off
To make a speed change permanent for eth0, set or add the ETHTOOL_OPT environment variable in /etc/sysconfig/network-scripts/ifcfg-eth0:
ETHTOOL_OPTS="speed 1000 duplex full autoneg off"
This environment variable is sourced in by the network scripts each time the network service is started.