IPv6 is enabled in the infrastructure to support customers with an IPv6 network over WAN and to connect the head office to branch offices in the local network. One of the customers is already running IPv6 and wants to enable IPv6 over the DMVPN network infrastructure between the headend and branch sites. Which configuration command must be applied to establish an mGRE IPv6 tunnel neighborship?
A. tunnel protection mode ipv6
B. ipv6 unicast-routing
C. ipv6 nhrp holdtime 30
D. tunnel mode gre multipoint ipv6
