No NAT November 2025

No NAT November was a buzz-term a few years ago. I could only find a few blogs about it. I thought I’d try it myself this year, at least for a bit. I’ve already deployed all of the IPv6 transition tech I possibly could, and my home network covers a broad range of use cases.

Deployed transition technologies

• IPv6 (RFC 8200): Obviously. I have a native /48 subnet from my ISP.
• DNS64 (RFC 6147): BIND9 DNS implements the “dns64” option.
• NAT64 (RFC 6052): Installed jool and integrated it with netfilter.
• PREF64 (RFC 8781): Configured radvd with the “nat64prefix” option.
• IPv6-Only Preferred (RFC 8925): Set “v6-only-preferred” (option 108) flag in kea DHCPv4.

After setting all of this up, the ultimate step is removing the “routers” option from DHCPv4, so that no route to the internet is advertised over IPv4. This is what I understand “no NAT” to mean. There is still a local IPv4 subnet. My server still has a public IPv4 address.

Observations

• XBox Series X: Despite removing the “routers” DHCP option, it took it upon itself to assume that 192.168.1.1 was a router and did it anyway. It’s possibly a failsafe for misconfigured networks, but it still cheated.
• Google Pixel (Android): These saw the v6-only-preferred DHCP flag and enabled CLAT. I did see one VoWifi bug which prevented most incoming calls. I narrowed it down to the UDP keepalive packets having no destination MAC address and being dropped. Google don’t care though.
• Samsung Phone (Android): These enabled CLAT and worked fine.
• Nintendo Switch: Had no internet connectivity whatsoever.
• Steam: Would not log in. Even when the underlying OS had full IPv6 network capability (but not CLAT). The bug was reported 11 years ago has not been acknowledged by Valve.
• Google Chromecast HD: My phone could not communicate with it when the phone was on CLAT. I suspect the Chromecast relies on IPv4 broadcast for discovery, and CLAT doesn’t really have a concept of subnets.
• Ubuntu Linux: No issues at an OS level. I tried clatd to see how it was. It technically worked, but the integration was terrible. I had to manually start the service to get it working.
• Microsoft Windows: It somewhat worked on my work computer, but I had issues where intellij wouldn’t communicate with github, despite git commands working directly from powershell.
• LG washing machine (2020 model): No connectivity.
• Rinnai air conditioner (2020 model with Midea wifi module): No connectivity.
• Hisense VIDAA Smart TV: Works without any issues.
• OzWeather Weather Station: No connectivity. There is now a huge gap in my Weather Underground data.
• Apple iPad: I’ve heard they have great CLAT support. I haven’t turned it on yet. I hate Apple.

Next year?

Microsoft have a CLAT implementation that has just entered a private preview in November 2025. By 2026, it may be a standard part of Windows. It’s nice to see them implementing a real OS feature instead of just monetising their user base.