Step 1: Create the config file
First, make a copy of the source file so that you can use it as a template:
cp /etc/sysconfig/network-scripts/ifcfg-eth0 /etc/sysconfig/network-scripts/ifcfg-eth0:0
Step 2: Edit the config file
You can now modify the eth0:0 file in order to replace the IP:
editor /etc/sysconfig/network-scripts/ifcfg-eth0:0
First, replace the name of the device, then replace the existing IP with the Additional IP you have received:
DEVICE="eth0:0"
ONBOOT="yes"
BOOTPROTO="static"
IPADDR="ADDITIONAL_IP"
NETMASK="255.255.255.255"
BROADCAST="ADDITIONAL_IP"
Step 3: Start the alias interface
You now need to start your alias interface:
ifup eth0:0