A customer with an IPv4 only network topology wants to enable IPv6 connectivity while preserving the IPv4 topology services. The customer plans to migrate IPv4 services to the IPv6 topology, then…

Dual stack enables network devices to run both IPv4 and IPv6 protocols simultaneously, allowing for the coexistence of both network types. This approach preserves existing IPv4 services while new IPv6 services are introduced and migrated, facilitating a gradual transition before IPv4 can be decommissioned.

6VPE (IPv6 VPN over MPLS) is a solution for transporting IPv6 over an MPLS IPv4 core, not a general strategy for migrating an entire enterprise network while preserving services.

6to4 is an automatic tunneling mechanism used to encapsulate IPv6 packets over an IPv4 network, primarily for connecting isolated IPv6 networks over the internet, not a full migration strategy to preserve services.

NAT64 is a translation mechanism that allows IPv6-only clients to communicate with IPv4-only servers, but it does not enable the existing IPv4 network to run IPv6 services simultaneously or facilitate a direct transition.