ewpratten.com/content/blog/2023-06-16-nat64.md

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page	How I set up NAT64	Working towards single-stack inside AS54041	2023-06-16	networking	true	auto_center_images excerpt uses true Information on how I set up NAT64 inside AS54041 mermaid

Somewhere along the way of setting up AS54041 over the past few years I stumbled across a reference to NAT64.

As with most things IPv6 related, Google searches surface a bunch of hand-wave-y information about possible implementations, but not much in the way of useful tutorials for anyone wanting to try it out themselves (without expensive enterprise routers that is).

A quick overview of NAT64

Firstly, traditional NAT (technically NAT44) refers to the process of mapping one IPv4 address range to another.

For example, residential networks generally NAT something like 192.168.1.0/24 to a single public IPv4 address. Every time an internal host wants to send a packet out to the other side of the NAT, a temporary port is allocated on the public address, the router keeps track of this mapping, and the packet is masqueraded from the public address.

graph RL subgraph Private IPv4 Address Space Host[Internal Host] --> Router Router --> Host end subgraph Public IPv4 Address Space Router --> Server[Remote Server] Server --> Router end

Now, if you are familiar with NAT44 (aka, NAT), NAT64 shouldn't be a crazy leap:

graph RL subgraph Private IPv6 Address Space Host[Internal Host] --> Router Router --> Host end subgraph Public IPv4 Address Space Router --> Server[Remote Server] Server --> Router end

Doesn't look like anything changed? Well, that's because the only difference is that the private network is IPv6 instead of 4.

Building on this idea of cross-protocol NAT, the next logical progression (and only way I've ever seen this implemented in practice) is to NAT between the whole IPv6 Internet and the whole IPv4 Internet. Like this:

graph LR Internet6((IPv6 Internet)) --> Router --> Internet4((IPv4 Internet)) Internet4 --> Router --> Internet6

I'm pretty sure NAT64 was originally intended to be used in an Anycast configuration, but I've yet to learn of anybody doing this in practice.

graph LR Internet6((IPv6 Internet)) <--> R1[Router 1] <--> Internet4((IPv4 Internet)) Internet6 <--> R2[Router 2] <--> Internet4 Internet6 <--> R3[Router 3] <--> Internet4

How I set up NAT64 on a Debian-based router

Final Remarks