A GRE tunnel shows '%TUN-RECURDOWN Interface Tunnel0 temporarily disabled due to recursive routing' — why is the tunnel disabled?

The error '%TUN-RECURDOWN Interface Tunnel0 temporarily disabled due to recursive routing' indicates a routing loop. This happens when the router determines that the best path to reach the tunnel's destination IP address is through the tunnel itself. Since the tunnel needs to be up to send traffic to its destination, and the destination is only reachable via the tunnel, a recursive dependency is created, preventing the tunnel from establishing. Incorrect options: Dynamic routing not being enabled is not the direct cause; static routes can also lead to this issue if misconfigured. While the tunnel cannot reach its destination because of the recursive routing, this option doesn't explain why it can't reach it. "Recursively identify its egress forwarding interface" is vague and doesn't precisely describe the routing loop problem.