In Linux you can add additional network IP's to a network interface with aliases.
Your first interface name looks something like etho. If you add more additional addresses your alias will look some thing like eth0:0 for the first one and eht0:1 for the second and so on.
This interface can be configured with it's own ip and subnetmask. If you need to route the traffic trough an special gateway you need to set up an detailed routing table for that because you only can set one default gateway on your system which is used if no special route is found.
Tony Bhimani wrote a real nice howto for RHEL which can be used for CentOS the same way.