The coexistence of IPv4 and IPv6 is the preferred solution for most network operators and enterprises. Dual stack deployment can support network devices to run IPv4 and IPv6 protocols at the same time, providing hosts with dual address access capabilities. To solve IP address compatibility issues, network engineers need to master a variety of conversion and transition technologies, including dual stack configuration, tunneling technology, and protocol conversion. What are the dual stack transition methods and implementation steps? How to ensure that the smooth launch of IPv6 applications will not affect the current IPv4 business premise, taking into account performance, security, and maintainability.
Enabling dual stack on the network boundary or core router is the most direct transition method. Enterprises can configure IPv4 and IPv6 addresses on firewalls, routers, and switch interfaces, and support both protocols on links and policies. In specific operations, first add the "ipv6 enable" or "ipv6 address" statement in the router interface command line to ensure that the core routing device can handle IPv6 routing and neighbor discovery protocol (NDP). At the same time, retain the original IPv4 routing table and policy, and gradually upgrade peer-to-peer devices to versions that support dual stack. On the DNS server and DHCP server, DDNS or DHCPv6 needs to be configured to register the host name and IPv6 address to the DNS together. Key business devices such as web servers, mail servers, and load balancers should also install operating system versions that support IPv6, and allow TCP/UDP port 6 (such as HTTP, HTTPS, SMTP, etc.) to pass through in the firewall policy.
For software or hardware that is still in the IPv4 network environment and cannot be directly upgraded, tunnel technology can be used to carry and forward IPv6 traffic. The 6to4 tunnel mechanism uses the 2002::/16 prefix to encapsulate IPv6 packets in the IPv4 relay network for transmission, and automatically identifies and decapsulates them on the edge router. When configuring specifically, specify "ipv6 6to4 relay anycast" on the 6to4 border router and enable the tunnel interface. The resulting 2002:WWXX:YYZZ::/48 network prefix. Among them, WWXX:YYZZ corresponds to the hexadecimal representation of the public network IPv4 address, which can achieve end-to-end IPv6 communication without changing the intermediate link. Although 6to4 provides zero-configuration deployment, it relies on public relay services and may cause unstable routing or translation delays.
Teredo tunneling is another solution for deploying IPv6 in a NAT environment. It encapsulates IPv6 on top of UDP/IPv4 and provides bidirectional mapping through Teredo servers and relay nodes. In the client configuration, you need to specify the Teredo server address and enable the Teredo tunnel driver in the Windows kernel. Although Teredo can traverse most NAT types, its performance is limited by UDP packet loss and the number of tunnel relays, making it unsuitable for latency-sensitive applications.
ISATAP (Intra‑Site Automatic Tunnel Addressing Protocol) is used for tunnel deployment within the same organization. ISATAP encapsulates IPv6 packets into IPv4, uses the ISATAP router within the organization as a tunnel hub, and supports peer-to-peer IPv6 communication. When configuring, you need to define an ISATAP interface on the IPv6 host and point it to the IPv4 address of the ISATAP router. ISATAP is suitable for gradually promoting IPv6 within an organization without replacing the IPv4 infrastructure, but it is not recommended for public network environments.
With the promotion of dual-stack networks, protocol conversion technology plays an important role. NAT64 combined with DNS64 can access IPv4 resources in IPv6-only networks. When the DNS64 server receives an AAAA record query, if the source station has no IPv6 record, it synthesizes an IPv4 mapping address with a prefix of 64:ff9b::/96. The request initiated by the client to the IPv6 address is decapsulated by the NAT64 gateway and accesses the IPv4 server. To deploy DNS64, you need to configure the synthesis policy on the DNS server and enable the NAT64 function on the gateway. This solution ensures the interconnection capability of IPv6-only clients, but increases the complexity of DNS and conversion gateways.
In order to take into account the flexibility of dual stack and conversion, MAP-T and MAP-E technologies can be used. MAP-T separates the IPv4 and IPv6 data planes in the CGN (Carrier-Grade NAT) scenario and uses address and port mapping rules to achieve stateless conversion; MAP-E provides a unified solution between tunnels and conversions, carrying converted traffic through tunnels to reduce the pressure on the central gateway. Operators can deploy MAPs on distributed nodes to reduce state synchronization requirements and improve scalability.
When implementing a dual-stack transition solution, security policies and monitoring mechanisms must be optimized simultaneously. IPv6 has a larger address space and stateless automatic configuration features, which increases network visibility and auditing difficulties. Firewall policies must support both IPv4 ACL and IPv6 ACL, and regularly audit IPv6 traffic rules. IDS/IPS systems, DDoS protection, and log management also need to be upgraded to support IPv6. The network monitoring platform should collect IPv6 traffic statistics, routing changes, and address usage to ensure full visualization of the dual-stack network.
Operation and maintenance personnel should develop a detailed migration plan during the deployment process. First, conduct an inventory assessment of network devices, servers, and applications to determine which devices can directly support dual stacks and which require tunneling or conversion, and then verify routing, DNS resolution, and application access in a test environment. During the deployment phase, different network segments can be launched in batches, first testing internal services and non-sensitive applications, and gradually expanding to core services. During the deployment process, the availability of IPv4 paths should be maintained, and the IPv4-only mode can be reverted at any time to prevent unexpected failures from affecting the business.
In order to promote the popularization of IPv6, enterprises can cooperate with upstream operators and cloud service providers to obtain native IPv6 links and address blocks. Native IPv6 networks reduce tunneling and conversion links, reducing the complexity and delay of operation and maintenance. When purchasing, ISPs that support dual stacks should be given priority, and end-to-end IPv6 test reports should be required. Enterprises can also participate in IPv6 seminars and training to improve the network team's mastery of the new protocol.
In summary, the transition from IPv4 to IPv6 dual stacks should be combined with dual stack deployment, tunneling technology and protocol conversion, and coordinated with the improvement of security strategies and operation and maintenance processes. Only with reasonable planning and phased implementation can enterprises gradually launch IPv6 applications while being compatible with IPv4 services.
