How to enable additional NIC (Network Interface Card) - RHEL
Enable Additional NIC (Network Interface Card)
If you have more than one NIC in your server and you want to enable any additional cards.
Run the following command, where ifcfgeth0, ifcfgeth1, or ifcfgeth2 is the numerical identifier of the ethernet interface you want to enable.
sed -i s/ONBOOT=no/ONBOOT=yes/ /etc/sysconfig/network-scripts/ifcfgeth0
Run the following command to restart the network interfaces: service network restart