Cisco Updated 400-007 Exam Questions and Answers by minahil

In DMVPN designs with many spokes, spokes may fail to receive periodic keepalives or routing updates if queues overflow during congestion, causing holding timers to expire and tunnels to flap. Increasing the hold queue size on the tunnel interface of the spoke routers allows them to buffer control plane packets during congestion and avoid premature tunnel teardown.

Why other options are incorrect:

A, C, E: Physical interface queues do not directly affect tunnel protocol timers.

D: QoS may help prioritize control plane traffic but doesn ' t address queue depth directly, which is the root cause of the issue.

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B (Point-to-multipoint network type): OSPF point-to-multipoint allows the hub to see the DMVPN topology correctly without complex neighbor relationships.

E (Set spokes priority to 0): Ensures the hub always becomes DR, maintaining predictable OSPF adjacency behavior.

Other options explained:

A: Broadcast mode is inefficient and unnecessary in DMVPN designs.

C: Mixed network types complicate adjacency maintenance.

D: Manually setting the hub priority is redundant when spokes are at priority 0.

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The scenario requires controlling how AS 111 sends its outbound traffic (egress traffic). BGP policy control for outbound traffic is best handled via manipulating the BGP Local Preference attribute, as:

Local Preference (LocalPref) influences path selection for outbound traffic by setting a preference for one path over another.

It is evaluated within the AS and does not require coordination with external autonomous systems.

LocalPref changes are fully contained inside AS 111 and satisfy the requirement to only affect AS 111.

A higher Local Preference value is preferred, thus you set higher values for routes learned via AS 100.

Why other options are incorrect:

A (community): Typically influences inbound traffic or interacts with upstream providers.

B (MED): Influences inbound traffic for external neighbors, not outbound.

D (AS Path): Also primarily influences inbound traffic selection by remote ASes.

B: Faster control plane convergence reduces the total recovery time after failure detection.

D: Enabling lower layer detection (such as BFD or physical layer link failure detection) shortens the time it takes to notify the control plane about link failure.

Why other options are incorrect:

A: Stability improves network operation but doesn’t address detection delay directly.

C: Interface flaps notification frequency doesn’t reduce initial detection delay — could actually create instability.

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