The primary consideration is that the participating hosts must support dual stack. The pilot is contained within a single VLAN, so the application traffic remains inside the same Layer 2 broadcast domain across the dual- site data center environment. Layer 2 switches forward Ethernet frames and do not need to understand the IPv6 header to carry IPv6 traffic inside the VLAN. Layer 3 switches need IPv6 capability only where IPv6 routing, gateways, ACLs, or services are required. For this pilot, the essential requirement is that the servers and endpoints running the IPv6 application can operate with both IPv4 and IPv6 enabled while the existing environment continues to support IPv4. Dual stack allows IPv6 testing without removing IPv4 reachability or forcing translation. Requiring every Layer 2 and Layer 3 switch in both data centers to be dual-stack overstates the design requirement. The hosts participating in the pilot are the critical dependency. Reference topics: IPv6 migration, dual stack, Layer 2 VLAN transport, data-center pilot design, IPv4 and IPv6 coexistence.