Refer to the exhibit.
As soon as the OSPF neighbors are established across the GRE tunnel between RTA and RTC,
the GRE tunnel immediately goes down/down. What could be a possible cause?
A.
The route to the tunnel destination is preferred via the tunnel.
B.
Autosummary is not configured.
C.
GRE tunnels cannot be in area 0.
D.
A misconfigured access list is on the router C tunnel interface.
E.
A misconfigured access list is on the router A tunnel interface.
Explanation:
The error message, %TUN-5-RECURDOWN: Tunnel0 temporarily disabled due to recursive
routing, means that the generic routing encapsulation (GRE) tunnel router has discovered a
recursive routing problem. This condition is usually due to one of the following causes:
A misconfiguration that causes the router to try to route to the tunnel destination address using the
tunnel interface itself (recursive routing).
A temporary instability caused by route flapping elsewhere in the network.
Tunnel interface status depends on the IP reachability to the tunnel destination. When the router
detects a recursive routing failure for the tunnel destination, it shuts the tunnel interface down for a
few minutes so that the situation causing the problem can resolve itself as routing protocols
converge. If the problem is caused by misconfiguration, the link may oscillate indefinitely.
Another symptom of this problem is continuously flapping Enhanced Interior Gateway Routing
Protocol (EIGRP), Open Shortest Path First (OSPF), or Border Gateway Protocol (BGP)
neighbors, when the neighbors are over a GRE tunnel.
This document shows an example of troubleshooting an oscillating tunnel interface that is running
EIGRP.http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094690.shtml