Solving the Hotel Network - Same Network ID Problem
You know the problem. You got off the plane, took a taxi to your hotel, and registered for your room. You get into your room and what's the first thing you do? No, you don't unpack your clothes and hang them up. What you do is take out your laptop and and hope and pray that you don't have problems getting connected to the Internet!
So you take out the laptop and turn it on. Do you find any wireless networks in range? Yes! And you're even able to connect to it. You open the browser and you see the log on page for the hotel network. Looks like this is going to be a good trip after all. You then browse to your favorite Web site to make sure the connection works and it does!
Now for the final test. Is your VPN connection going to work? You double click on your VPN connectoid and wait for the connection to establish. It connected! That's great. It's going to be a good day. Now you try to connect to the file server on your home or corporate network and it can't connect. What's up with that?
You open a command prompt and type ipconfig /all and your worst fears are realized -- your hotel network has assigned you an IP address on the same network ID as your home or business network! Now it's going to be impossible to connect to your network through the VPN. You know that's true because you know the VPN connection is a routed interface, and thus you need to be on a different network ID.
The way I've solved this problem in the past was to use a wireless router. You connect the hotel interface to the WAN port on the router and then have the router assign an IP address to the wireless client that is on a different network ID. While the solution works, it means carrying around more gear and it doesn't always work.
Is there a better solution? There sure is! Yuri Diogenes from Microsoft PSS in Las Colinas, Texas documents a great solution where you just manipulate the routing table on your client machine. Even better, Yuri documents how you can leverage the CMAK to make this setting available to all your users, so they don't need to figure out how to edit the routing table themselves.
Instead of me rehashing his solution, you should read his blog for the details. All you need to know is there. Check it out at:
Thomas W Shinder, M.D.
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MVP — Microsoft Firewalls (ISA)