Networking across campus with multiple ISPs

Question

I currently have a campus that gets service from two ISP's that are each connected to their own router. The ISP's ingress and their routers are in different buildings on the campus. The buildings are not networked currently.

I have a requirement to install cameras across campus and have those networked into a single NVR and accessed by a browser anywhere on campus. There is no other requirement for load balancing across ISP's or need for redundancy. The only requirement is to receive video feed from the cameras to the NVR and play/replay on a computer browser on either network.

From a physical wiring standpoint, I can easily connect the networks from a switch in one building to a switch in another. I cannot so easily connect the two routers together directly without going through a switch. Any ideas on a fairly simple solution to this problem would be appreciated.

Answer 1

Before one can start to make a plan for solving a problem like this one needs a lot more information.

• What are the "routers"? are they "serious" routers from major network equipment vendors? are they generic computers being used as routers? are they soho type routers?
• What are the "switches"? are they unmanaged or managed?
• What is the network addressing in the two buildings? is there any overlap? if so, is renumbering feasible?
• Who is responsible for these networks now and in the future?
• Is more general network connectivity between the buildings desirable, undesirable or something no-one cares about?

Armed with this information, a plan can be devised. If the routers are proper routers or computers used as routers and there are no network address conflicts, then a transfer subnet and appropriate routes is the obvious solution. If the switches support vlans then vlans can be used to isolate the transfer subnet while passing it over existing physical infrastructure.

OTOH if there are address conflicts, or "soho" type routers are in use then other solutions may be needed.

Answer 2

The easiest method is to connect the two routers using a dedicated, routed port on a small transfer subnet (/30 or /31) and add a static route to the remote network on each side. If network addresses overlap you need to renumber one of the subnets (thx @Ron).

If each network connected to a local router is just a single subnet then that's all there is to it (otherwise add more static routes as required).

If you can't use additional, routed ports on the routers, you can add a router or L3 switch in between, connected to both networks, and add a static route to the remote network on each WAN router with the new router as gateway.