To add a interface you need to do the following,

  1. Confirm what the mac address is by running ifconfig -a
  2. Then edit the relevant script , which can be found at /etc/sysconfig/network-scripts/ifcfg-eth0. The script can be ifcfg-eth1, ifcfg-eth2 etc etc.
  3. And it should look something like this (for a static IP),

IPADDR=10.10.10.111
DEVICE=eth0
HWADDR=00:02:Z3:F8:LE:4D
NETMASK=255.255.255.0
GATEWAY=10.10.10.100
ONBOOT=yes

  4. Reboot your system.