Steps in WHM:
You can change primary ip in whm very easily
1.just Log into WHM and go to Basic cPanel & WHM Setup
2. Change Primary IP
And the 2nd way Log in to SSH:
1. Edit it by using
#vi /etc/sysconfig/network-scripts/ifcfg-eth0
to Change the IPADDR
2. vi /etc/sysconfig/network –to change the gateway
3. vi /etc/ips —–> remove the primary ip
4. vi /var/cpanel/mainip —–>replace with old to new
5. vi /etc/hosts —>>>> Replace with old to new IP
6. /etc/init.d/network restart
7. /etc/init.d/ipalias restart
8. /usr/local/cpanel/cpkeyclt —>to refresh the licence.
http://www.stradsolutions.com/linux-vps.php