Which method allows IPv4 and IPv6 to work together without requiring both to be used for a single connection during the migration process?

Which method allows IPv4 and IPv6 to work together without requiring both to be used for a single connection during the migration process?
A . dual-stack method
B . 6to4 tunneling
C . GRE tunneling
D . NAT-PT

Answer: A

Explanation:

Dual stack means that devices are able to run IPv4 and IPv6 in parallel. It allows hosts to simultaneously reach IPv4 and IPv6 content, so it offers a very flexible coexistence strategy. For sessions that support IPv6, IPv6 is used on a dual stack endpoint. If both endpoints support Ipv4 only, then IPv4 is used. Benefits: Native dual stack does not require any tunneling mechanisms on internal networks Both IPv4 and IPv6 run independent of each other Dual stack supports gradual migration of endpoints, networks, and applications.

Reference: http://www.cisco.com/web/strategy/docs/gov/IPV6at_a_glance_c45-625859.pdf