One Port, One Computer: The problem is that my router settings will only let me forward Port 8333 to one IP address (or computer). It will not let me set more than one IP to forward to the same Port 8333.
I'm sure there must be an easy way around this [i.e., in layman's language], but I cannot find it anywhere. Can someone help me with this?
Unless your home network has unusually good bandwidth to the Internet it is unlikely that you could provide much service to the bitcoin network by running more than one bitcoin node. At present, I don't have any node mapped to receive incoming connections. Given my slow upload DSL bandwidth anyone who happened to connect to me to download the block chain would have to wait many days due to my limited bandwidth, so I figure I would actually be doing them a disservice. A better way to service the network from a slow connection is to seed the bootsrap.dat torrent.
If you want to run multiple bitcoin nodes on your LAN for various reasons (such as testing), then I suggest dedicating a stable machine to be your "front" machine. If you want that one to serve the network, then map 8333 to it at your router. Your other bitcoin nodes can have a "connect=192.168.1.xx" command in their config file. That way they won't put any burden on the network. Also, they can clone the blockchain quickly over your LAN.