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Flet'HFlet'H Docs

Flet'H Architecture and Modes

This documentation is still being edited and may differ from the actual version.

Flet’H is not a separate router operating system. It runs on OpenWrt and turns common Japanese IPv4 over IPv6 setups such as DS-Lite, MAP-E, static IP, and independent IP into LuCI protocols, status pages, and helper scripts.

Where it fits in OpenWrt

Section titled “Where it fits in OpenWrt”

LuCI pages
These are the Network -> Flet'H page and the protocol options in Network -> Interfaces. They handle configuration input, detection results, port ranges, and line status.

netifd protocol
Flet'H IPoE is an OpenWrt network protocol. After you save and apply the interface, OpenWrt netifd calls the Flet’H backend script to bring up the IPv4 over IPv6 tunnel.

Detection and calculation scripts
Flet’H reads the upstream IPv6 interface, usually wan6, then detects DS-Lite AFTR or MAP-E parameters. For MAP-E, it calculates the IPv4 address, BR address, PSID, and usable port ranges.

Main modes

Section titled “Main modes”

Flet’H IPoE
Most users should start here. It automatically tries DS-Lite or MAP-E detection and fits common services such as v6プラス, transix, Xpass, and IPv6オプション.

Flet’H Static IP
Use this for static IPv4 or independent IPv4 plans. These usually require IPv4, IPv6 endpoint, or prefix information from the ISP.

Flet’H Static IP (Passthrough)
Use this when the public IPv4 address should be handed to a DMZ-side firewall, business router, or server. Ordinary home NAT setups usually do not need this mode.

Why wan6 comes first

Section titled “Why wan6 comes first”

Flet’H assumes OpenWrt already has working IPv6. Without IPv6, DS-Lite, MAP-E, and IPIP6-style static IP setups cannot work.

That is why the setup flow is:

  1. Connect the ONU to OpenWrt.
  2. Confirm that wan6 has an IPv6 address or prefix.
  3. Create the Flet’H interface.
  4. Check the detection result in Network -> Flet'H.

Continue with the classic setup flow.