300-410 Question 157
Select 2A company has deployed a DMVPN solution to interconnect its branch offices to the headquarters over the public Internet. The network engineer notices that traffic between branch offices is being routed through the headquarters instead of going directly between the branches. Which of the following steps should the engineer take to enable direct branch-to-branch communication in the DMVPN setup?
- A
Enable NHRP shortcut on the branch routers.
- B
Configure GRE keepalives on the tunnel interfaces.
- C
Ensure that the spoke routers are configured as NHRP spokes.
- D
Enable IPsec encryption on the branch-to-branch traffic.
- E
Enable 'no ip split-horizon' on the hub router's tunnel interface.
Show answer and explanation
Correct answers: A, E
Explanation
To enable direct branch-to-branch communication in a DMVPN solution, the engineer must configure NHRP shortcuts on the branch routers so they can dynamically resolve other spoke addresses and establish direct connections. Additionally, disabling split-horizon on the hub router's tunnel interface ensures that routes learned from one spoke are advertised to other spokes, making direct communication possible.
- A. Correct.
Enabling NHRP shortcut allows spoke routers to dynamically resolve and establish direct branch-to-branch tunnels without routing traffic through the hub.
- B. Incorrect.
GRE keepalives are used to monitor the health of the tunnel interfaces but do not affect the traffic path selection or direct branch-to-branch communication.
- C. Incorrect.
Configuring the spoke routers as NHRP spokes is necessary for DMVPN, but this alone does not enable direct branch-to-branch communication.
- D. Incorrect.
IPsec encryption secures the traffic but does not influence the routing path or enable direct communication between branches.
- E. Correct.
Disabling split-horizon on the hub router's tunnel interface allows the hub to advertise routes learned from one spoke to other spokes, which is crucial for enabling direct branch-to-branch communication.