300-410 Question 170
Single answerAn enterprise is deploying a single-hub DMVPN configuration. The hub router is configured with the appropriate NHRP settings and tunnel interface, but the spoke routers cannot communicate with each other directly. Which of the following configurations on the hub router will allow direct spoke-to-spoke communication via the DMVPN network?
- A
Configure the hub router's tunnel interface with 'ip nhrp redirect'.
- B
Enable 'no ip split-horizon' on the hub router's tunnel interface.
- C
Configure the spoke routers with static routes to each other.
- D
Enable 'ip nhrp shortcut' on the hub router's tunnel interface.
Show answer and explanation
Correct answer: A
Explanation
In a single-hub DMVPN configuration, the hub router must be configured with 'ip nhrp redirect' to support direct spoke-to-spoke communication. This command allows the hub to notify spoke routers to bypass the hub when communicating directly. Without this configuration, all traffic between spokes will pass through the hub, preventing direct communication.
- A. Correct.
Correct: The 'ip nhrp redirect' command is required on the hub router to inform spoke routers to establish direct spoke-to-spoke tunnels in a DMVPN Phase 2 or Phase 3 configuration.
- B. Incorrect.
Incorrect: Disabling split-horizon is not required for spoke-to-spoke communication in a DMVPN configuration. This command is more relevant to routing protocols in other scenarios.
- C. Incorrect.
Incorrect: Configuring static routes on the spoke routers is not necessary in a DMVPN setup because NHRP dynamically resolves next-hop addresses.
- D. Incorrect.
Incorrect: The 'ip nhrp shortcut' command is applied on spoke routers, not the hub router, to enable direct spoke-to-spoke communication.