[url]http://www.fogproject.org/wiki/index.php?title=FOGUserGuide#Location_Plugin[/url]
You can set up the location plugin, as Junkhacker said.
Basically, you set it up to control storage nodes that reside within each broadcast domain in your entire network. It’s a several step process to add the location plugin, and it’s done through the FOG web GUI. I don’t know about setting up the storage nodes, but I do believe there’s an option specifically for this during FOG’s installation.
I’m currently in the process of better documenting this plugin because, contrary to popular belief among regular FOG users, I find it not simple. I hope to produce some excellent documentation within a few weeks to be listed within the WiKi.