350-401 Question 507
Select 3You are tasked with configuring a single-hub DMVPN topology for a company with multiple branch offices. The hub router is configured with a static public IP address, while the spokes use dynamic public IP addresses. Which two configurations are critical on the hub router to ensure successful DMVPN operation?
- A
Configure the hub router with the 'ip nhrp map multicast dynamic' command.
- B
Enable the 'ip nhrp network-id' command in the DMVPN tunnel interface.
- C
Use the 'ip nhrp map
' command for all spokes. - D
Set the tunnel mode to 'gre multipoint' on the hub router.
- E
Apply the 'tunnel key' command to match the hub and spoke tunnel interfaces.
Show answer and explanation
Correct answers: B, D, E
Explanation
In a single-hub DMVPN topology, the hub router acts as the central point for all spoke-to-spoke and spoke-to-hub communication. Configuring the 'ip nhrp network-id' ensures proper NHRP operation, while 'tunnel mode gre multipoint' enables the hub to communicate with multiple spokes. The 'tunnel key' command ensures the logical DMVPN network consistency. These configurations are critical to the functionality of the DMVPN network.
- A. Incorrect.
The 'ip nhrp map multicast dynamic' command is used on the spokes, not the hub, to enable dynamic mapping for multicast traffic. It is not required on the hub router.
- B. Correct.
The 'ip nhrp network-id' command is mandatory on the hub router's DMVPN interface and must match across all devices in the DMVPN network. This ensures NHRP operates correctly.
- C. Incorrect.
The 'ip nhrp map
' command is unnecessary on the hub router in a dynamic DMVPN setup because the spokes use dynamic IPs and register themselves via NHRP. - D. Correct.
The 'tunnel mode gre multipoint' command is crucial on the hub router to enable communication with multiple spokes using a single tunnel interface.
- E. Correct.
The 'tunnel key' command ensures that the hub and spokes are part of the same logical DMVPN network. This is required for successful communication.