There are a small variety of methods to implement failover of your WAN perimeter between two ISPs. In this post we’ll look at one way to accomplish this goal with a few technical requirements.
Keep in mind that there are several ways to accomplish this same goal depending on the hardware available, the flexibility of the ISPs, and the skill level or preference of the engineer.
This topology utilizes two edge routers and two ISPs instead of the single edge router design I wrote about recently (you can read that here). For this post we’re using Cisco routers, but the concepts apply universally. Our requirements are that we maintain connectivity from our inside host to the internet in the event one of the company routers fails or one of the ISPs fails. Failover and fail-back must be automatic with no manual intervention.