I have a little problem. I can’t work out how to make my default route resilient to various connections going down.
Take the simple example below of a full mesh WAN. Routers 0, 1 and 2 are all private network ips managed via OSPF. Router 0 is connected to Router 3 which is the internet (via NAT/PAT). This is the only route to the internet for all devices.
Private network communications are kept working in the event of a failure. I.e. if the connection between R0 and R2 fails, R2 can still communicate with R0 via R1 for private traffic. However, what if R1 or R2 needs to get out to the internet?
I have static default routes on R1 and R2 which point to R0. In the event of a failure that static route might not be available, so I’d want it to switch instantly to the other router, which will then forward on the traffic. However, I can’t manager this with OSPF (I think) because it’s unknown, public traffic.
If I set two static default routes then 50% of the traffic will succeed (round robin), but this isn’t what I want. I want my default route to switch when unavailability is detected.
What am I missing?