When you are configuring a hub-and-spoke DMVPN network, which tunnel mode should you use
for the spoke router configuration?

A.
GRE multipoint

B.
Classis point-to-point GRE

C.
IPsec multipoint

D.
Nonbroadcast multiaccess

Explanation:
http://www.cisco.com/en/US/docs/solutions/Enterprise/WAN_and_MAN/DMVPN_2_Phase2.html
The hub-and-spoke deployment model is the most common deployment model. This model is the
most scalable, and predominately mimics traditional Layer 2 leased line, Frame Relay, or ATM
hub-and-spoke networks. The headend is configured with a multipoint GRE (mGRE) interface, and
the branch with a point-to-point (p2p) GRE interface.