WAN IP address for LAN with public IPs?

Question

Given a computer with 2 network cards, one for WAN, the other one for LAN and some public IPs 123.1.2.0/24. Now the computer shall connect all LAN clients to the outside, without NAT or any further filtering (except for limiting internet access from some specified clients by MAC address, but that's not my problem). So, I disabled NAT and assigned 123.1.2.0/24 to the LAN interface. Now I am little bit confused: What will be the WAN address in this case?

Thanks for any hint and sorry for this probably noobie question, but at the moment I simply don't get it ;-)

Answer 1

If you've been assigned 123.1.2.0/24, this is four your LAN network. You still need another IP address, from another network, for the connecting segment (if you have a router, this is the connection between your router, and your providers' router). Your provider has to give you an address for the WAN interface, and set up his routing, so the route to your 123.1.2.0/24 will be via your WAN address.

If your provider is doing all the routing, you just need a switch, and he has to tell you the gateway address from the 123.1.2.0/24 network, which resides on his router.