Doublestack

Doublestack, often referred to as double-stack or dual-stack, is a network design approach in which devices, networks, or services run both IPv4 and IPv6 protocol stacks concurrently. The goal is to enable communication with endpoints on either IP family without requiring translation or tunneling in every case, allowing a seamless transition from IPv4 to IPv6.

In practice, doublestack is implemented on hosts, servers, routers, and other network infrastructure. Each interface typically obtains both an IPv4 address and one or more IPv6 addresses, and routing tables are configured to handle traffic for both protocol families. Applications and services can then communicate with resources across either IPv4 or IPv6 networks. This approach supports mixed environments where some endpoints are still IPv4-only and others have moved to IPv6.

Implementation considerations include operating system support, DNS configuration, and address management. Doublestack increases the complexity of network administration, requires careful routing and firewall rules for both IPv4 and IPv6, and can raise security and monitoring concerns. In IPv6-only networks, mechanisms such as NAT64 or translation gateways may be used to reach IPv4 hosts, while in some cases tunneling or carrier-grade NAT is involved to bridge gaps.

While doublestack remains a common strategy during IPv6 adoption, many organizations are evaluating alternatives such as IPv6-only deployments with translation layers. The choice depends on compatibility requirements, performance considerations, and long-term migration plans.