After the recent implementation of a new design that incorporated GRE tunnels into the network, the network operations staff is seeing the following syslog message in multiple routers on the network…

Hold time expiration refers to routing protocol neighbor timers going down due to missed hello packets - this produces a different syslog related to the routing protocol adjacency, not the GRE-specific RECURDOWN message.

If the local tunnel source interface were down, IOS would generate an interface-state change syslog and the tunnel would fail to come up, but it would not produce the recursive routing error message.

A down interface on the remote router would cause tunnel keepalive failures or an inability to establish the tunnel, not a recursive routing condition on the local router.

Recursive routing occurs when the routing table's best path to the tunnel endpoint IP address points back through the tunnel interface, meaning the tunnel depends on itself to stay up. IOS detects this loop and generates %TUN-5-RECURDOWN, temporarily disabling the interface to prevent a forwarding storm. The design oversight was not ensuring the tunnel destination is reachable via a physical interface - either through a more-specific static route or by constraining the underlay routing protocol to exclude the tunnel interface.

Missing keepalives produce a keepalive-related tunnel error when tunnel keepalives are explicitly configured - recursive routing is a distinct routing table problem unrelated to keepalive timers.