Aberystwyth Stunet (Turning a WRT54GS into a straight switch)

Posted by Neil Crosby on October 25, 2004 04:30 PM

I learnt last week that the University of Wales, Aberystwyth’s Information Services people had at some point in the past year or so decided to lift the limit which said that each room in halls could only have one MAC address (and therefore only one PC) registered to it. If I’d learnt this a couple of weeks prior, I might have saved myself a little bit of money. You see, when I got my iBook I decided to buy myself a nice shiny new router (the Linksys WRT54GS). I registered the WRT54GS MAC address on the aber system, and life was good. Both my main Windows PC and my new iBook could access the internet simultaneously - the Windows machine by a wire, the iBook wirelessly. They could share files between each other, and stream videos. It was all good.

Except that it wasn’t. There were some things that I just couldn’t do any more. I couldn’t easily access other students’ shared files on the university network, unless I knew their IP address. I couldn’t use iTunes to listen to shared music (except that which was inside my little network). Worst of all, I couldn’t print to the university’s networked printers from my room, which was a real hassle.

But then, as luck would have it, one of my friends completely randomly told me that Information Services would allow you to register more than one MAC address. So, I went up to them, and registered the addresses of both my actual PCs again. Unfortunately, I then had to work out how to get the WRT54GS working purely as a switch. Here’s what I did:

• First and foremost, I removed the network cable that connected the WAN port of the WRT54GS to the network port on my wall. Instead I connected between the wall, and one of the LAN ports on the back of the WRT54GS
• I then went into the router’s setup webpages and turned off the internal DHCP server
• Finally, because the University’s uses 255.255.248.0 as its subnet, I changed the subnet mask on the WRT54GS. I had already installed the firmware from sveasoft which allowed me to do this.
• I rebooted the router, disabled and re-enabled the network connection in Windows, and lo and behold, I’d been given IP addresses on both my machines on the aber network.

And that’s how I did that. Hopefully that will come in useful to someone else - I found it quite hard to find this information on the internet.

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