Iptables and ip aliasing?

[Andreas]

Hi,
I've got a firewall with 3 interfaces on, one internal nic, one external 
and one for the dmz.

Today we only have one ip address, which is a fully routable address on 
the external nic. But we're expanding and getting a whole c-class net. I 
  know that I can use ip aliases to replicate the external nic with more 
addresses, like this:
eth0:1
eth0:2
etc

But I've read somewhere that Iptables does not work with ip aliases. How 
do I make my firewall have say 5 ip addresses on the external nic, with 
iptables working? Is it possible?

Regards,
Andreas