Which common issue causes intermittent DMVPN tunnel flaps?

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#1

Which common issue causes intermittent DMVPN tunnel flaps?
A. a routing neighbor reachability issue
B. a suboptimal routing table
C. interface bandwidth congestion
D. that the GRE tunnel to hub router is not encrypted

Correct Answer: A

Explanation:
DMVPN Tunnel Flaps Intermittently
Problem
Dexter ITC
DMVPN tunnel flaps intermittently.
Solution
When DMVPN tunnels flap, check the neighborship between the routers as issues with neighborship formation between routers may cause the DMVPN tunnel to flap. In order to resolve this problem, make sure the neighborship between the routers is always up.