We can configure secondary ip address in centos by using the following steps but make sure that you have logged in to the server as root user.
cd /etc/sysconfig/network-scripts
Create the new interface file ifcfg-eth0:1, if its already exist then use ifcfg-eth0:2 and so on for the every new ips.
touch ifcfg-eth0:1
Now open the file ifcfg-eth0:1 and add the following lins as per your ip new ip address.
DEVICE=eth0:1
BOOTPROTO=static
IPADDR=your new ip address
ONBOOT=yes
Similarly you can add other ips on your server and to get the ip up use the ifup command.
