Assigning Two Static Public Ips


hi,I have just got a triband connection in Mumbaiwith two public IPs. these IPs I want to use for Cisco PIX firewall and a VOIP device.MTNL the ISP has provided me with UT STARCOM 300R2UMTNL guys say that they can assign IPs to the eqipmentments which can dial in to the BB Router like Desktops and Laptops and work. but there present technological know how doesnot let them assign IP statically to the equipments like PIX firewall and VOIP device simultaneously.if any one of you know how to do it with MTNL. kindly let me know. So that I could speed up my work of setting and using the broadband in efficient manner.