300-440 Question 181
Select 3You are configuring a DMVPN Phase 2 deployment using NHRP. After the initial setup, you notice that spoke-to-spoke communication is not working, and all traffic is being routed through the hub. Which of the following configuration steps would resolve this issue?
- A
Enable the 'ip nhrp redirect' command on the hub router.
- B
Enable the 'ip nhrp shortcut' command on the spoke routers.
- C
Configure the 'ip split-horizon eigrp' command on the hub router.
- D
Disable the 'ip split-horizon eigrp' command on the hub router.
- E
Enable the 'ip nhrp map multicast dynamic' command on the spoke routers.
Show answer and explanation
Correct answers: A, B, D
Explanation
In a DMVPN Phase 2 deployment, spoke-to-spoke communication requires the hub to redirect spokes to communicate directly with each other. The 'ip nhrp redirect' command on the hub and 'ip nhrp shortcut' on spokes enable this functionality. Additionally, split-horizon needs to be disabled on the hub to allow routing updates from one spoke to reach others, ensuring proper spoke-to-spoke communication.
- A. Correct.
Enabling 'ip nhrp redirect' on the hub router is required in DMVPN Phase 2 to inform spoke routers about the optimal spoke-to-spoke communication path.
- B. Correct.
Enabling 'ip nhrp shortcut' on the spoke routers allows them to dynamically learn and create direct tunnels to other spoke routers for direct communication.
- C. Incorrect.
The 'ip split-horizon eigrp' command enables split-horizon, which prevents routing updates received on the hub from being sent back out the same interface. This is not desirable in DMVPN since spokes need to exchange routes through the hub.
- D. Correct.
Disabling 'ip split-horizon eigrp' on the hub router ensures that routing updates received from one spoke can be forwarded to other spokes, facilitating spoke-to-spoke communication.
- E. Incorrect.
Enabling 'ip nhrp map multicast dynamic' is useful for multicast traffic in DMVPN but does not directly affect spoke-to-spoke communication issues.