I've got a situation with three locations each with their own subnet (something like 192.168.1.0/24, 192.168.2.0/24, 192.168.3.0/24) are linked with OpenVPN site-to-site. All three subnets are exported at the server and everything works splendidly most of the time thanks to the default routing in OpenVPN.
On each of the three subnets are servers, workstations, other SCADA hosts and still other CAM serial device server hosts. Aside from running low on IP addresses on some of the subnets, I'd like to get the building automation and CAM devices off the business network for sanity reasons.
Brainstorming, if I setup three more subnets for the the SCADA and CAM hosts I'm still left with one problem. Most of these hosts use protocols that rely on broadcasts for discovery. BACnet would be a good example and recently I've come to realize the drivers for the Moxa serial servers seem to be doing something similar. They can see peer devices on the subnet they're attached to but not the others. Implementations also vary for these embedded devices but it's usually not possible to do routing at the host or sometimes even specify a broadcast address other than the expected default.
I wondered if anyone here knows of a clever way of adjusting the routing tables or perhaps exporting a virtual 10.0.0.0/8 subnet with a single broadcast address that would span the three physical locations.