Dual Stack

Running IPv4 and IPv6 Simultaneously

Dual-stack is the recommended transition strategy for migrating from IPv4Internet Protocol version 4. The fourth revision of IP using 32-bit addresses (e.g., 192.168.1.1), providing approximately 4.3 billion unique addresses. Still the most widely used internet protocol despite address exhaustion. to IPv6Internet Protocol version 6. The successor to IPv4 using 128-bit addresses (e.g., 2001:0db8::1), providing a virtually unlimited address space of 3.4 x 10^38 addresses. Designed to solve IPv4 address exhaustion.. A dual-stack host or router maintains independent addresses in both protocol families and can originate or receive traffic using either. When a dual-stack client resolves a Domain NameA human-readable address (e.g., example.com) that identifies a website or service on the internet. Domain names are registered through registrars and resolved to IP addresses by the DNS system., the DNSDomain Name System. The hierarchical, distributed naming system that translates human-readable domain names (e.g., example.com) into IP addresses (e.g., 93.184.216.34). Often called the "phonebook of the internet." resolver returns both an A RecordA DNS record that maps a domain name to an IPv4 address (e.g., example.com -> 93.184.216.34). The most fundamental DNS record type for resolving domain names to IP addresses. (IPv4) and an AAAA RecordA DNS record that maps a domain name to an IPv6 address. Named "AAAA" (quad-A) because an IPv6 address is four times the size of an IPv4 address. (IPv6). The client operating system uses the Happy Eyeballs algorithm (RFC 8305) to race IPv6 and IPv4 connection attempts and use whichever completes first — typically preferring IPv6 when both succeed equally.

Infrastructure Requirements

Operating dual-stack requires address allocation in both families. IPv4 addresses are obtained from an ISPInternet Service Provider. A company that provides internet access to consumers and businesses, assigning public IP addresses and routing traffic to the wider internet. Examples include Comcast, AT&T, and SK Broadband. or RIR, often through NATNetwork Address Translation. A method of remapping private IP addresses to a single public IP address (and vice versa) at a router, allowing multiple devices to share one public IP. A key technique for mitigating IPv4 address exhaustion. for private ranges. IPv6Internet Protocol version 6. The successor to IPv4 using 128-bit addresses (e.g., 2001:0db8::1), providing a virtually unlimited address space of 3.4 x 10^38 addresses. Designed to solve IPv4 address exhaustion. prefixes are typically /48 or /64 per site, with abundant address space for sub-delegation. Routers must run BGPBorder Gateway Protocol. The routing protocol that exchanges reachability information between autonomous systems, effectively determining how data traverses the internet. Often called the "postal service of the internet." or OSPFOpen Shortest Path First. An interior gateway routing protocol that uses link-state advertisements and Dijkstra's algorithm to compute the shortest path within an autonomous system. for both address families, and FirewallA network security device or software that monitors and filters incoming and outgoing traffic based on predefined rules. Firewalls can block traffic by IP address, port number, protocol, or application-layer content. rules must be maintained separately for each. Many operators discover that IPv6 firewall rules lag behind their IPv4 equivalents, creating security gaps.

Alternative Transition Mechanisms

Where dual-stack is impossible — for example, an ISP that has exhausted IPv4 addresses — transition mechanisms like 464XLAT, DS-Lite, and MAP-T provide IPv6-only access with IPv4 translation at the network edge. These mechanisms are increasingly common on mobile networks. Pure IPv6-only deployments without any IPv4 fallback remain rare for public services because significant portions of the internet, particularly older ISPInternet Service Provider. A company that provides internet access to consumers and businesses, assigning public IP addresses and routing traffic to the wider internet. Examples include Comcast, AT&T, and SK Broadband. infrastructure, remain IPv4-only.