The service provider that you work for wants to offer IPv6 internet service to its customers without upgrading all of its access equipment to support IPv6. Which transition technology do you recommend

CGN (Carrier Grade NAT) performs NAT44 to extend IPv4 address space but does not introduce IPv6 addressing or provide IPv6 internet service to customers.

NAT64 (RFC 6146), used with DNS64, enables a service provider to assign IPv6 addresses to customers and translate traffic to IPv4 at the network border, so that intermediate access equipment handling only IPv4 does not need to be replaced or upgraded to route native IPv6. This lets the SP deliver IPv6 internet service to customers without a full infrastructure overhaul, as the NAT64 gateway performs stateful protocol translation between the IPv6 customer side and the IPv4 internet.

Dual-stack CPE requires upgrading customer premises equipment to support both IPv4 and IPv6 simultaneously, which contradicts the goal of avoiding equipment upgrades.

6RD (IPv6 Rapid Deployment, RFC 5969) tunnels IPv6 over an existing IPv4 access network but requires 6RD-capable CPE at each customer site and a border relay, meaning customer-edge equipment still needs to be replaced or upgraded.