Here you go: http://www.howtoforge.com/perfect_setup_centos_4.3_p3
Now we want to create the virtual interface eth0:0 with the IP address 192.168.0.101. All we have to do is to create the file /etc/sysconfig/network-scripts/ifcfg-eth0:0 which looks like this (we can leave out the HWADDR line as it is the same physical network card):
Name the next file ifcfg-eth0:1 and put the info for the 2nd IP in it..
Same for ifcfg-eth0:2 and ifcfg-eth0:3 ....