After posting Farewell to Airport Base Station a reader who also suffered from slow NTT Flets internet speeds asked for a few details to help him troubleshoot his own setup.

Before starting out here is a warning: rental devices from NTT and internet providers like So-net are constantly being updated with firmware updates, backend services running on them are constantly updated as well. NTT Router IPv6 and PPPoE IPv6 settings shown in online documentation may not match router settings of the most recent firmware versions. Also remember that rental NTT router models are different depending on your connection plan.

When in doubt confirm with NTT Flets or your internet provider tech support.

My Setup

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I have a NTT Flets Hikari Phone + ‘Mansion’ internet connection plan with So-Net as the internet provider. As I wrote in the first piece, IPv4 traffic is extremely congested in my local area which So-net tech support checked and confirmed. So-net suggested their free IPoE IPv6 option service as a possible solution.

Unfortunately my AirPort Express Base Station was not very good routing IPv6 traffic. Even in Bridge mode most of the network traffic outside of YouTube remained stuck in the clogged IPv4 stream. This makes sense as AirPort was conceived in the IPv4 era and Apple isn’t updating the software features anymore. The So-net IPoE IPv6 support site mentions that Apple routers “may not be compatible.”

The So-net site does list NEC, BUFFALO and I-O DATA WiFi Routers that are compatible with IPoE IPv6. The key is IPv6 Bridge / IPv6 Pass-Through support which all of them appear to have.

Instead of buying my own WiFi router to replace the AirPort Extreme however, I decided to rent a So-net WiFi router preconfigured for IPoE IPv6 service and DS-Lite (IPv4 over IPv6). The So-Net WiFi router is free for the first 7 months, ¥400 a month there after. So-net tech support said I could return the router at any time in the first 7 months, no questions asked. These things can change so be sure to confirm any rental agreement with your internet provider.

NEC, Buffalo and I-O DATA WiFi Routers can be configured for DS-Lite and Map-E as well but after a year of wrangling with AirPort Extreme configurations, I was done with doing my own IPv6 setup.

I ran with both AirPort Extreme and the So-net rental WiFi router for a few weeks until I was sure IPoE IPv6 and DS-Lite were working OK, then pulled the plug on AirPort. The only tweak on the So-net WiFi router side was renaming the default WiFi network names and login passwords.

The final step was shutting off PPoE on the NTT router. PPoE is a IPv4 only legacy technology and leaving it on can hamper DS-Lite/IPoE performance. The easiest thing to do is reset the NTT router to factory defaults and do not set it up for PPoE.

Confirming IPv6
There are some simple ways for NTT Flets and So-net customers to confirm if IPv6 running correctly:

1) NTT Flets IPv6 Speed Test site If IPv6 is configured correctly you can access the site and test NTT Flets connection speed.

2) Download the Ookla SpeedTest App from the Mac App or iOS App Store. If So-net IPoE IPv6 and DS-Lite are correctly configured your should see “INTERNET MULTIFEED” as the home network name.

UPDATE: Choosing the right WiFi router for Japan NTT FLETS

I used AirPort since the first generation in 1999 and always found the AirPort series to be reliable and easy to configure. But starting in mid 2016 I noticed my NTT Flets mansion (PPPoE – VDSL) service slowing down to analog modem speeds at night and during the weekends.

And so began a year-long tech support journey with NTT and internet provider So-Net to find the problem. Many configuration tests, speed tests, and traceroutes later one thing was clear: IPv4 traffic in Suginami Tokyo was chronically congested. It was time to switch to IPv6 service which So-Net offers as a free option.

The IPv6 option came with a warning: “some of our customers have problems accessing sites like Amazon or Rakuten and switch back to IPv4.” I took the plunge anyway and tried using Airport Extreme (Generation 8) via PPPoE bridging and IPv6 tunneling options.

That worked better than the previous IPv4 only setup at first but it wasn’t long before using the internet after 9 pm was impractical. I then tried using Airport Extreme in bridge mode. That helped for a while but nighttime internet speed degraded over time, by summer of 2017 I was back at square one.

Another set of tests later So-Net tech support suggested a So-Net wireless router for free (the first year) “tuned for routing IPv4 over IPv6.” At wit’s end I decided to give the NEC ATERM WG1810HP wireless router a try. Like magic my internet speed problems were over.

Poking through the ATERM settings I noticed everything was preset for DS-Lite, clearly optimized for NTT FLETS. It’s also clear from reading Japanese forum posts that the NTT FLETS transition to DS-Lite has been in place for some time and AirPort Extreme routers are not equipped for the change. With Apple getting out of the wireless router business time to say goodbye to AirPort Extreme. It was a good run.

UPDATE: Choosing the right WiFi router for Japan NTT FLETS