I've got two hosts running the same release of RHEL (6.4). I've been given eight IP addresses to put onto one NIC in each host. On host A, I manually created ifcfg-eth0, ifcfg-etho:1, ifcfg-etho:2, ...
There appear to be (at least) two ways to add a secondary IP address to an interface on Linux. By secondary, I mean that it'll accept traffic to the IP address, and responses to connections made to ...