What i wanted to do was to have 2 web servers having private IPs( Ex: 192.168.128.5 and 192.168.128.6 on the 255.255.255.0 subnet). The hub connecting these machines would be connected to my Linux firewall machine. In other words the private IPs are the ones that make my DMZ, I shall call this interface which is connected to the DMZ as eth1.
What i want to do is redirect all requests to 64.24.12.45 to 192.168.128.5 and 64.24.12.46 to 192.168.128.6 at the moment i have no problem in doing the natting and everything related to send/receive from the 64.24.12.45.
What i thought was to have a virtual interface and bind the other internet routable address to it, ex eth0:0. What are my options?
Also how could i do the POSTROUTING SNAT if I cannot use virtual in terfaces?

iptables doesn't support virtual ip aliasing. So you really have two ways to do this. First you can buy new NICs for the additional IPs.

Alternatively, you can setup virtual IPs like you've explained. Despite the fact that iptables doesn't support IP aliases, it will recognize traffic on the virtual interface as being on the same device as the normal interface device (so eth0:0 and eth0:1 would both appear as eth0 to iptables). The trick then, is to use other attributes of the packets to distinguish how the SNATing should work.

For example say you want all web traffic being NATed from one of the internal boxes to be SNATed as one IP and all traffic coming from the other internal webserver to get SNATed as the other external IP. In this case you could use the type of traffic (http) and the source address (192.168.128.5 or 192.168.128.6) and the interface the traffic would be leaving(eth0) to define the SNATing:

iptables -t nat -A POSTROUTING -p tcp --sport 80 -o eth0 -s 192.168.128.5 -j SNAT --to-source 64.24.12.45

iptables -t nat -A POSTROUTING -p tcp --sport 80 -o eth0 -s 192.168.128.6 -j SNAT --to-source 64.24.12.46

You might have to tinker around with the other rules as well, but hopefully that will give you a start.

You find that I can decide the problem using iproute (IP addr)?