GRE Tunnel Recursive Routing Error

Hello Mark

By definition, a GRE tunnel will connect two tunnel interfaces on two different routers across a network such as the internet, as if they are directly connected. So by definition, these interfaces must be on the same subnet. In other words, you’re tricking the routers into thinking they’re directly connected. Two directly connected routers must have their interfaces on the same subnet. Does that make sense?

I hope this has been helpful!