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japan:phone-and-internet

Internet connectivity in Japan

My internet connection notes

Provider of the physical media (光回線) and the connectivity provider ontop (プロバイダー) are separated in Japan. I'm on NTT flets for physical: a fiber cable goes into the whole building, into a delivery room (MDF室). From there fiber runs to my room. From there, one has these options:

  • With a SFP-GE-PON connector into a PR-500KI device, NTT call it “home gateway”. The device combines modem and router (speaking pppoe) functionality. The PR-500KI does not support port forwarding or UPnP-port-forwarding.
  • Alternatively, one can get a small fiber SFP connector (小型ONU) from NTT. NTT marks these as compatible with a selection of some select router models. These routers are not very interesting for me though: expensive, older, not allowing own firmware.
  • Alternatively, one can get a plain “modem” from NTT (called “GE-PON型 FA光加入者線終端装置タイプD” or ONU(Optical NetWork Unit). The modem does not speak PPPoE, an own router or Linux system has to be connected and configured for PPPoE.

Ontop of the physical connection, an IP provider has to be contracted. I'm with Biglobe, did not care to much about this when subscribing - but payed attention they offer IPv6, which I had to explicitly enable with an option on a website. Biglobe seems focused on normal end customers, so changing IPv4 addresses are to be expected.

Modem/router details

In 2024, I got aware that plain modems were possible - so got one and returned the “home gateway”. For router, 2 devices were interesting:

The Linksys is much cheaper, and even if buying the GL-MT6000, it would not offer the upcoming Wifi7.

Taking the Linksys into usage, installing OpenWRT, was quite painless with exception of IPv6: with the homegateway, I think I had a complete IPv6 segment delegated to my LAN, and was running IPv6 services like SSH, webserver. The router did no packet filtering. With the Linksys/OpenWRT, I get via DHCPv6 delegated an IP with /64, but not a bigger segment.

  • I did not manage to distribute IPs from that segment to my LAN
  • IPv6 relay config works for me
  • Also NAT6 works for testing, but IPv6 relay config is preferable.

There are other ISP/IP layer providers which can be used and offer static IPv4 IPs, for offering services - details are here.

OpenWRT notes

opkg update
opkg list
opkg install atop
opkg list-upgradable
opkg upgrade wireless-regdb urngd
japan/phone-and-internet.txt · Last modified: 2024/02/23 08:06 by chris