Go to /etc/sysconfig/network-scripts
Make multiple copies of ifcfg-eth0 and name them as ifcfg-eth0:0, ifcfg-eth0:1 etc.
Open each of them and at least change the IPADDR to your chosen IP address and the NETMASK to the subnet mask for that IP address.
A sample entry would look like this:
DEVICE=eth0:0
BOOTPROTO=static
IPADDR=34.123.111.21
NETMASK=255.255.255.0
ONBOOT=yes
Restart the network:
/sbin/service network restart
You are done!
