How to Set Up IPv6-Only Networks with NAT64/DNS64

The global transition to IPv6 is inevitable as IPv4 addresses continue to run out. Many organizations are adopting IPv6-only networks, which simplify operations and prepare infrastructure for the future.

However, a challenge remains: most of the internet still relies on IPv4. To bridge this gap, administrators use NAT64 and DNS64, technologies that allow IPv6-only clients to communicate with IPv4 servers.

This article explains:

• What NAT64 and DNS64 are
• Why they’re essential for IPv6-only environments
• Step-by-step setup guidance
• Best practices for deployment

Understanding NAT64 and DNS64

NAT64

• Network Address Translation 64 allows IPv6-only devices to access IPv4 resources.
• It translates IPv6 packets into IPv4 packets and vice versa.
• Works similarly to NAT in IPv4 but specifically designed for IPv6-to-IPv4 communication.

DNS64

• A complementary DNS service that synthesizes AAAA (IPv6) records from A (IPv4) records.
• When an IPv6-only client queries for a domain that has only an IPv4 address, DNS64 generates a corresponding IPv6 address that points to the NAT64 gateway.

Together, DNS64 + NAT64 provide seamless communication between IPv6-only clients and legacy IPv4 services.

Why Use IPv6-Only with NAT64/DNS64?

• Future-proofing: Moves away from legacy dual-stack networks.
• Simplified management: Only one protocol (IPv6) to administer internally.
• Conservation of IPv4 addresses: Reduces reliance on scarce IPv4 resources.
• Compatibility: Clients can still reach IPv4-only services.

Network Design Overview

A typical setup includes:

1. IPv6-only clients (workstations, servers, IoT devices)
2. DNS64 server (synthesizes AAAA records)
3. NAT64 gateway (translates traffic)
4. IPv4 internet or internal resources

Flow:

• Client queries DNS64 → DNS64 generates IPv6-mapped address → traffic goes through NAT64 → translated into IPv4 → response returned via the same path.

Step-by-Step Setup

Step 1: Enable IPv6 on Clients and Network

Ensure that all client devices, routers, and switches support IPv6. Disable unnecessary IPv4 configuration if aiming for an IPv6-only environment.

Step 2: Deploy a DNS64 Server

Many modern DNS servers support DNS64, including BIND, Unbound, and Windows DNS Server.

Example (BIND configuration snippet):

options {
    dns64 64:ff9b::/96 {
        clients { any; };
        exclude { ::ffff:0.0.0.0/96; };
    };
};

This tells DNS64 to synthesize IPv6 addresses in the 64:ff9b::/96 prefix range, which is reserved for NAT64.

Step 3: Configure a NAT64 Gateway

Popular implementations include TAYGA (Linux), Jool (Linux), or hardware-based solutions in enterprise routers/firewalls.

Example (TAYGA on Linux):

# /etc/tayga.conf
tun-device nat64
ipv4-addr 192.0.2.1
prefix 64:ff9b::/96
dynamic-pool 192.0.2.0/24

Start TAYGA and configure the system’s routing to direct IPv6 traffic into the NAT64 gateway.

Step 4: Update Routing and Firewall Rules

• Ensure IPv6 clients send queries to the DNS64 server.
• NAT64 must be positioned so that it can route to both the IPv6 and IPv4 sides.
• Update firewall rules to allow NAT64 traffic.

Step 5: Test the Setup

From an IPv6-only client, try accessing an IPv4-only site:

ping ipv4.google.com

If DNS64 + NAT64 are functioning, the client will receive a synthesized IPv6 address and the connection will succeed.

Best Practices

• Use the well-known prefix 64:ff9b::/96 for NAT64 unless you require custom prefixes.
• Deploy redundant DNS64 servers for high availability.
• Monitor NAT64 translation logs to identify frequently accessed IPv4 services.
• Educate users about IPv6 transition—some legacy applications may still have issues.
• Plan a phased migration: start with lab testing → limited deployment → enterprise rollout.

Advantages and Limitations

Advantages

• Seamless IPv6-to-IPv4 communication
• Reduces dependence on IPv4
• Enables IPv6-only deployments

Limitations

• Doesn’t support IPv4-only applications that embed IP addresses directly (e.g., hardcoded IPv4 literals)
• Adds translation overhead
• Requires careful monitoring and troubleshooting

Conclusion

Configuring IPv6-only networks with NAT64/DNS64 is a key step toward full IPv6 adoption. While dual-stack networks remain common today, NAT64/DNS64 allows organizations to simplify internal infrastructure while maintaining compatibility with the IPv4 world.

By carefully planning, configuring, and monitoring, administrators can future-proof their networks and take advantage of IPv6’s scalability and efficiency.