@tomtom2770 So let me discuss what FOG needs to work in your environment.
The master node is kind of the brains of the FOG system since it houses the fog database.
The storage nodes are disk storage for deploy only. It needs to be in contact with the FOG server 100% of the time for the storage node to remain functional.
So lets say you have 1 sites HQ and SiteA. You have a master node at HQ and a storage node at SiteA. At SiteA you have the dhcp options to point to the local storage node and the needed boot file.
You pxe boot a target computer at SiteA. It downloads the boot file from the local storage node and iPXE starts up. Then iPXE reaches out to the local storage node to download default.ipxe file. That file points to your master node boot.php script which builds the iPXE Menu. If the computer isn’t registered, when you select register it will download FOS Linux (over the wan) from HQ to the target computer. (once the computer is registered and associated with a location, the storage node will be used for all other file transfers).
Now if you have the fog client installed on the target computer it will only talk to the master node to get instructions (install snapin, update inventory, etc). If the target computer get an instruction to install a snapin, that snapin is downloaded from the local storage node.
So the point here is that the HQ fog server is important here and must be at a fully routable location from all remote sites.
If your site to site VPN ever goes down so does FOG imaging. Depending on your goal, number of client computers, and stability of the VPN network, you might want to install a full fog server at each location.