Why worry about routers and switches? Unless I'm missing something the OP can simply connect his usual device running the Cisco NAC software, and run a wifi hotspot off that PC (easy under Linux, even easier under Windows) to share the connection with unlimited wifi devices in his room while showing only a single machine IP to the network. No router, or expensive kit, required. Just an onboard ethernet card or mobo jack, and a £5 wifi dongle. (Edit: In fact he mentions a laptop which will have ethernet and wireless N built in anyway).
If the OP would rather have ethernet connections as stated (for the X-Box) he could add a second ethernet card to a desktop PC, and use it as a router. Else, just put it on wifi and suck it up. Better than no connection at all if the uni refuse to allow a router.
	
		
			
		
		
	
				
			If the OP would rather have ethernet connections as stated (for the X-Box) he could add a second ethernet card to a desktop PC, and use it as a router. Else, just put it on wifi and suck it up. Better than no connection at all if the uni refuse to allow a router.

			
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