forcing first page on network

Just a question I've been pondering every since I visited a hotel over the summer...

How do you force a first page on a wireless network?

For example, Joe connects to a Hotel wireless network...before he can reach the internet, he is presented with a front page where he must agree to TOS and click to continue...

How can you force the viewing of that first page on a wireless network? I'm not talking about an "in-house" robust network (with a proxy server), but can this be done from the router?

Can you set up a web server as part of the WAN that forces the showing of that first page?

I've seen it done a dozen times, but I can't figure it out.

You can't do it with consumer grade equipment.

Usually it's done in that your MAC address, when it first appears on network, is checked against a database. If you are not in the database, your web request will automatically be forwarded to a web page for authentication. The router in the network usually takes care of this.

Once you have authenticated, your MAC addresses is added into the database and you are then allowed to browse freely.

My network device at home is a Netscreen 5GT Wireless. It's enterprise grade and it has this feature built into it. It just depends on what your wireless device is, but most home gear doesn't have this capability.

I'm sure you can do something like this with a linux/freebsd box in the network though, just your wireless device acting as the layer2 connectivity and all layer3 traffic sent to the *nix box.