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Updated on May 21, 2025
NAT64 is a Network Address Translation mechanism that allows IPv6 hosts to communicate with IPv4 hosts by converting IPv6 packets to IPv4 and vice versa through a NAT64 gateway. It’s a crucial tool for IT professionals managing IPv6-only networks needing compatibility with IPv4 devices or content.
Definition and Core Concepts
The core functionality of NAT64 lies in its ability to provide seamless translation between IPv6 and IPv4 networks. Achieving this requires a deep understanding of the following foundational concepts:
IPv6 Addressing
IPv6 is the next-generation internet protocol designed to replace IPv4. It offers an expanded address space with 128-bit addresses, enabling a nearly infinite number of unique IP addresses. IPv6 also introduces features such as simplified header structures and support for multicast communication, enhancing performance and efficiency.
IPv4 Addressing
IPv4, the predecessor of IPv6, uses 32-bit addresses, allowing for approximately 4.3 billion unique addresses. Due to the rapid growth of internet-connected devices, IPv4’s limited address space has led to the adoption of IPv6.
Network Address Translation (NAT)
NAT modifies packet headers as they pass through a NAT gateway. This process enables devices sharing a single public IP address to access external networks and facilitates protocol translation between IPv6 and IPv4.
Gateway
The NAT64 gateway acts as the translator that mediates communication between two incompatible protocol versions. It translates packet headers and addresses while maintaining the integrity of data transfer.
Address Mapping
Address mapping ensures that every IPv6 address has a corresponding IPv4 address for translation and vice versa. This linkage is crucial for seamless connectivity.
Protocol Translation (Limited)
NAT64 supports limited protocol translation. This is particularly critical for specific applications where IPv6-only devices integrate with legacy IPv4 infrastructure.
Stateless vs. Stateful NAT64
- Stateless NAT64 maintains a one-to-one mapping between IPv6 and IPv4 addresses. It is simpler but less flexible, as it requires each IPv6 host to have a corresponding IPv4 address.
- Stateful NAT64 allows multiple IPv6 hosts to share a single IPv4 address, conserving resources and providing additional flexibility.
How It Works
NAT64 operates through a set of defined processes to handle both outbound and inbound traffic, ensuring robust communication between IPv6 and IPv4 networks.
IPv6 to IPv4 Translation
Outbound traffic: IPv6 hosts use the NAT64 gateway to send packets to IPv4 destinations. The gateway translates the IPv6 headers into IPv4 headers, including source and destination IP addresses, before forwarding the packets to the IPv4 network.
IPv4 to IPv6 Translation
Inbound traffic: IPv4 hosts can initiate communication with IPv6 hosts through the NAT64 gateway. The gateway changes the IPv4 headers into IPv6 headers while mapping the addresses appropriately.
Address Mapping Rules
NAT64 relies on mapping rules to link IPv6 network prefixes with IPv4 address ranges. These rules determine how addresses are converted and routed.
Handling of Port Numbers
NAT64 modifies port numbers as needed during translation to ensure unique identification of sessions and facilitate smooth data transmission.
DNS64 Functionality
DNS64 works alongside NAT64 to resolve DNS queries for IPv6-only hosts accessing IPv4 content. When an IPv6-only device requests the DNS record of an IPv4-only server, DNS64 synthesizes an AAAA record (IPv6 format) from the server’s A record (IPv4 format), enabling communication.
Key Features and Components
NAT64 offers a range of features and components designed to enhance interoperability and efficiency during IPv6 transition:
- IPv6 to IPv4 Interoperability: Facilitates communication between IPv6 and IPv4 devices without modifying the end-point hosts.
- Enables IPv6-Only Devices: Allows IPv6-only devices to access IPv4 content seamlessly.
- Gateway Requirement: Relies on a NAT64 gateway to manage address translation and protocol conversion.
- Performance Overhead Potential: While effective, NAT64 translation processes may introduce performance overhead, making optimization critical.
Use Cases and Applications
NAT64 is widely utilized in scenarios where IPv6 and IPv4 coexist, enabling organizations to adopt IPv6 incrementally without sacrificing compatibility.
IPv6-Only Networks Accessing IPv4 Internet
Organizations with IPv6-only networks require NAT64 to provide access to legacy IPv4 content, ensuring uninterrupted connectivity during the transition phase.
Gradual IPv6 Deployment Scenarios
Enterprises transitioning to IPv6 infrastructure can use NAT64 to maintain interoperability with IPv4-dependent devices and services until full deployment is achieved.
Mobile Networks Transitioning to IPv6
Mobile networks are increasingly adopting IPv6 to address scalability challenges. NAT64 ensures that IPv6-enabled mobile devices can communicate seamlessly with older IPv4 systems and services.
Key Terms Appendix
- NAT64: Enables communication between IPv6 and IPv4 networks through address and protocol translation.
- IPv6 Addressing: A 128-bit addressing scheme introduced by IPv6, offering an expanded address pool and improved functionality.
- IPv4 Addressing: A legacy 32-bit addressing scheme still used by the majority of internet devices today.
- NAT (Network Address Translation): Modifies network packet headers to allow communication between devices using different IP address schemes.
- Gateway: A device or software component that translates packets between different protocols or networks.
- DNS64: A DNS mechanism that creates synthetic AAAA records to allow IPv6-only devices to access IPv4-only servers.
