Which interface configuration must be configured on the spoke A router to enable a dynamic DMVPN tunnel with the spoke B router?

Refer to the exhibit.

Which interface configuration must be configured on the spoke A router to enable a dynamic DMVPN tunnel with the spoke B router?

A)

B)

C)

D)

A. Option A

B. Option B

C. Option C

D. Option D

View Answer

Answer: B

Explanation:

The command “ip nhrp map multicast dynamic” should be only used on Hub router, not spoke. If we are running dynamic routing protocols based on multicast (like RIP, OSPF, EIGRP …) we have to add the command “ip nhrp map multicast dynamic” in Hub to replicate all multicast traffic to all dynamic entries in the NHRP table (multicast will be proceeded as unicast traffic) -> Answer A is not correct. Also another error in this answer is the “tunnel source” IP address. It should be the NBMA address of the Spoke interface: 172.17.0.2.

Answer C is not correct as the “tunnel source 1.1.1.10”, “ip nhrp map 10.0.0.11 172.17.0.2” and “tunnel mode gre” are wrong.

Answer D is not correct as there is no “ip nhrp map multicast static” command, only the “ip nhrp map multicast <static-IP>“ command is available. The “tunnel source 10.0.0.1” is not correct either.

Answer B is correct. The “ tunnel source FastEthernet0/0″ is equivalent to “tunnel source 172.17.0.2”, which is the NBMA address of Spoke A.