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Bubulle's weblog, Random bits from Christian Perrier

Christian Perrier
christian@perrier.eu.org

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IP over DNS for dummies
Once again, I'm sitting in an airport (CDG) and enjoying the benefits of IP over DNS to bypass the outraegous rates for wireless access (about 10 euros for 1h if that didn't change since last year).

Actually, having IP over DNS work is pretty simple. What you need is:

• A domain that you control (ie you can create en entry in it)
• A server running DNS services on the Internet, preferrably with a static IP address, preferrably with no need of external DNS services
• Appropriate software

You then need to create an entry in your foo.bar domain, such as "tunnel.foo.bar" and have it point to your static address.

Then you run iodine on that server, listening to port 53 (with a configured password). That creates a virtual interfaces with something like 10.0.0.1 as address.

When you need IP over DNS access with your roaming laptop, all you need is to connect to the expensive network, then launch iodine and provide it two parameters: the "tunnel.foo.bar" address and a local address (for instance 10.0.0.2). If everything works well, you'll be prompted for the password and voilà. You have a tunnel between your local 10.0.0.2 address and the remote 10.0.0.1.

The rest is a matter of network routing and you can now access the entire Internet through your remote server with no charge. The entire traffic goes through DNS requests to the local DNS server. That can be fairly slow but all a geek needs is receiving/sending mail and remote SSH access, right?

This doesn't work in every place, unfortunately. Many wireless providers block such traffic in some way. But, at least in Aéroports de Paris, I can promise that will work..:-)

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