" The edge routers can handle failing over the link from one provider to the other, we'd need a small static IP block for each provider with at least 3 assignable addresses to do failover correctly. No need for a second wifi network, or infrastructure. Once we have the edge routers, make the primary resolver the edge routers, make the edge router forward requests for internal zones to the AD dns servers. This eliminates huge chunks of failure pain points and can be achieved in about 2 hours once we have the hardware. Second connection is a little more complicated, but we could fix a lot of stuff with one purchase of the edge router.