A GRE tunnel is down with the error message %TUN-5-RECURDOWN: Which two options describe possible causes of the error? (Choose two.)

Question

Options

• AIncorrect destination IP addresses are configured on the tunnel.
• BThere is link flapping on the tunnel.
• CThere is instability in the network due to route flapping.
• DThe tunnel mode and tunnel IP address are misconfigured.
• EThe tunnel destination is being routed out of the tunnel interface.

• A
  5% (1)
• B
  14% (3)
• C
  71% (15)
• D
  10% (2)

Explanation

GRE Tunnel Recursive Routing Error Explanation

The %TUN-5-RECURDOWN error specifically indicates a recursive routing problem, meaning the router is trying to route traffic destined for the tunnel endpoint through the tunnel itself, creating an infinite loop - this is exactly what option E describes. Option C is also correct because route flapping causes the routing table to oscillate, which can repeatedly trigger the recursive routing condition, causing the tunnel to go down intermittently.

Why the distractors are wrong:

• A (incorrect destination IP) would prevent the tunnel from forming at all, but generates a different error, not RECURDOWN
• B (link flapping) describes a physical/interface instability issue unrelated to recursive routing
• D (misconfigured tunnel mode/IP) would cause configuration errors, not the specific recursive routing loop that RECURDOWN indicates

Memory Tip: Think of "RECUR" in RECURDOWN as "RECURsive" - the router is chasing its own tail trying to route the tunnel's destination back through the tunnel. Ask yourself: "Is my tunnel trying to eat itself?" If the tunnel destination lacks a specific static route or the routing table points it back into the tunnel, you'll see this error.

No community discussion yet for this question.