My network dilemma...
 

Alright, I am in a dorm with 2 network outlets in each room, one for each person.
I have an xbox and Halo-2 is quite popular on the campus and by plugging the network cable into the xbox, we can play anybody on campus by System Link (as opposed to Xbox Live).
The problem is that it is a pain in the ass to have to unplug the cable from my computer each time.

I was trying to find a RJ-45 splitter to have both connected at the same time using the single RJ-45 port. I found this:
http://www.mcmcomputers.co.uk/
Unfortunately, there is no link to the actual product, but you click on 'Network Accessories' at the top and it is at the bottom of the list (about 20 items).

Thanks in advance for all help!

First, that kicks ass that you can play Halo with everybody in the dorm without having to pony up the money for xbox live. Second, I tried a RJ-45 splitter I found at your locel radio shack but I couldn't get the thing to work. Why can't you just get a router? I don't know about configuring the xbox to it but usually they're PNP anyway. Here's one on newegg for $32.

Router

Soccer, you're trying to simulate a passive hub. It could be done depending on the wiring you're using but you may as well buy a finished product. They're dirt cheap and don't require any special configuration. I've seen bushels of the things hit the trash after being replaced by switches. Check with any school resources that might packrat old equipment.

This seems to be for rare situations where two shotgunned nics needs to have their signals rejoined for network transport. If I'm reading that right (which I very well might not be), then this is not what you are seeking.

Can you just set up a router and place the first port in a DMZ to connect correctly to the campus xbox consoles? Just set the first router port in a dmz with no blocked ports, and have the rourter imitate the mac address of the xbox console perhaps?

wouldnt using 2 network cards work? i think thats what ^ he was saying.

It really depends whether every port is assigned only a single IP. If the campus has a DNS pile big enough to run all the boxes, then a switch should do the trick (with the uplink port plugged into the wall). Both the PC and Xbox would get an IP from the DNS server. If you are only allowed one IP each, then the router it the best way to go.

Kolila is suggesting putting a second network card in your PC and using ICS to share the connection, but it is probably more hassle and not much more cost than a router anyway...

Just buy a cheap 4 port switch or hub. And IP addresses are assigned by DHCP servers, and unless your campus has a very limited number of addresses it shouldn't be a problem at all.