How to use Real IP inside the LAN

[Sandeep Agarwal]

Dear All,

I have following setup.

ISP---->|eth0|Linux Box|eth1|------>|Switch|--->PC (LAN IP)
                                                            |--->VOIP Device 
(Cisco) (Real IP)
                                                            |--->WebServer 
(Real IP)

ISP has provided 8 IP Pool.
No DMZ configuration is there. Simple rc.firewall is working.
Now I want to use Real IP inside the LAN.
What is the right way to do this?

Will it be worthwhile, If I make aliases like eth1:1 & assign a Real IP from 
pool?
If this is ok, than which rules I have to add in iptables?

Thanks
Sandeep