I have to change the subnet mask on all my cpanel servers in a few days. I'm wondering, is it enough if I change the file "/etc/sysconfig/network-scripts/ifcfg-eth0"? Or is there anything else needed?

I use 2 ip addresses per server, but I can not find a ifcfg-eth0:1 file for the second IP. I have only one network card. How can I change the subnetmask for the second IP?

I use Centos 3.5 with WHM/Cpanel.