DNAT Problem

[Jesse.linux]

hi there....   i have a Linux box 7.1 and it has two network interface... eth0 = external eth1 = internal   i've made my box as a Gateway/Firewall for other servers located internally...i am connected by a dsl connection and my isp provided me 5 static ip's   let say that these are my static ip's a.b.c.130 - 134   and i've already used a.b.c.130 to my eth0....now my problem is how can i assign the remaining static ip's to my servers in my internal network that is , i want my servers behind my firewall to have their private ip's translated to my remaining static ip's?   thanks in advance....