Generally hubs and switches don't have anything to do with IP addresses, all they do is forward packets from one port to another (or all ports in the case of a hub) based upon MAC address. Some hubs and switches can have an IP of their own for management purposes, but that usually has no bearing on how they forward packets.
A router connects two or more networks and forwards packets between them to make them work like one big network. The term WAN IP usually just means the IP that's non-local, for instance if you connect a router to your ISP and your network the cable from your ISP would be the WAN side. But if you use a router to connect one subnet on your local network to another subnet technically neither are the WAN.
What I think you're thinking of is NAT, a way for a router to hide the IP addresses of the machines behind it. Using NAT all the machines behind a router could connect to the Internet but the remote hosts on the Internet would see all the requests as coming from the 1 WAN IP on the router. You can probably find a better description if you look for Linux docs on IP Masquerading or using FreeBSD or OpenBSD as a NAT firewall, they'll have some OS specific things in them but the general ideas are the same.
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