Two computers, one MAC address

  LeadingMNMs 21:17 11 Sep 2005

I'm going back to university in a few weeks, and this year I have two computers, one XP and a Linux box.

The halls will provide a single ethernet port and access is limited by providing a MAC address. At home, the connection to the Internet is provided by a router, which obviously hides the computers and there MAC addresses, showing only routers MAC (I think I'm right).

I'm sure it must be possible to get this to work, but I'm not exactly sure what I need. Will a router (without modem) configured correctly do the job ? Or will a simple switch be able 'mask' the MAC address ?

Also, will there be any problems with the DHCP allocating addresses to the machines ? Presumably, behind a router, the IP addresses can be anything, with the routers assigned by the server. Presumably , with a switch with IP addresses will have to be assigned by the server to each machine (and the switch).

I hope that makes sense.

  LastChip 21:45 11 Sep 2005

The Router will be recognised by the Universities servers as your MAC address and then your Router will assign addresses to your computers.

As far as the University is concerned, your Router is your computer. It will also give you the added advantage of a strong Firewall, as most Routers now include one.

There is an alternative. You can hack the XP registry and fake the MAC address (make it the same as your Linux box), but it's a messy way of dealing with the problem and of course, you would only be able to use one machine at a time.

  LeadingMNMs 18:42 12 Sep 2005

Thanks for that, I think thats cleared it up.

One more thing, most routers allow you to spoof a MAC address. I assume that it wouldn't cause any problems if the router and computer behind it had the same MAC address, otherwise it would be a bit pointless. The only reason I'm asking, is that I think it'll probably be easier to get the connection on my computer, let DCHP assign the IP address and subnet mask and then manually enter these into the router - since I'm not entirely sure that I'll be able to get the router running to start with.

One last thing, and it probably doesn't really matter, but do I connect the router to the network, using one of the ethernet ports, or to the WAN port that would normally go to a modem ? I'm guessing it won't matter, as long as the routers gateway is pointing to the universities server / router.

  Taran 19:15 12 Sep 2005

You may want to check with your university about their support for routers, and then make sure yours can cope with uplink.

More and more educational buidlings are being locked down a little tighter, and the large college I am involved with runs IP monitoring. All networks are capable of this really, but many aren't as well set up as they could be.

If our network notices an unusual IP transferring data it flags an alert and sometimes automatically locks said IP address from transfer.

Think of it like this: most routers are on or similar. Depending on their DHCP server address range, your may have a range starting at or similar.

So although your router is the first 'computer' attached to your available port and will be identified by MAC address and, in all probability, by its IP address, the sub-IP addresses it issues to the systems attached to it could start alarm bells ringing.

It all depends really, on how paranoid the network manager is and how capable his or her staff are.

Most routers have an ADSL connection for the built in modem, some will also have ISDN, but a standard router without built in modem will be a better bet for this protject.

I've seen some small travel routers recently (Linksys have one coming out soon) that plug straight into an RJ45 network port and they, in turn have two ports for cables to link computers into. Ideal for hotels, universities...

It's worth checking before charging on ahead.


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