HOWTO: CentOS: Multiple IP’s
It’s simple really.
Create a file /etc/sysconfig/network-scripts/ifcfg-eth0:0 [eth1:x for 2nd interface etc.] containing:
DEVICE=eth0:0
ONPARENT=yes
IPADDR=192.168.1.1
BROADCAST=192.168.1.255
NETMASK=255.255.255.0
NETWORK=192.168.1.0
Manipulating the interface manually:
Bring it up: /sbin/ifup eth0:0
Take it down: /sbin/ifdown eth0:0
The ONPARENT option will automatically bring it up and down in conjunction with the parent interface eth0.
To remove automatic behaviour, just delete or move the file away somewhere else.