LAN IPv6 Configuration

These steps were checked on LuCI in OpenWrt 25.12. Field names and locations may vary in other versions, so adjust them to match what you see on your router.

When wan6 has IPv6, the OpenWrt router itself can reach upstream IPv6. LAN clients such as PCs, phones, and Wi-Fi devices still need OpenWrt to distribute IPv6 on the LAN side.

This is the situation described in the classic setup flow: the router itself may have IPv6, but LAN clients may still have no network.

Check the line type first

Open:

Network -> Interfaces -> wan6

Check the wan6 status:

Status shown	Treat it as
IPv6 PD is shown	DHCPv6-PD
no IPv6 PD, but a global IPv6 address is shown	SLAAC / RA
neither is shown	Go back to Before Install: Get OpenWrt Online and fix wan6 first

Do not rely only on the contract name. In LuCI, the IPv6 PD and IPv6 rows in the wan6 status are the practical signals.

Recommended: Flet’H Tool (Automatic)

After installing Flet’H, open:

Network -> Flet'H -> ツール

Under LAN IPv6 設定, click the button that matches your line:

Line	Click
DHCPv6-PD	PD (/56)
SLAAC / RA	SLAAC (/64)

The button updates wan6, lan, and DHCP / RA related settings, then restarts the relevant services. After it finishes, check wan6 and a LAN-side client in Network -> Interfaces.

Manual Configuration

Depending on the wan6 status, perform one of the following:

DHCPv6-PD

Use this when wan6 status shows IPv6 PD. This is common on フレッツ 光クロス, or on フレッツ 光ネクスト with ひかり電話.

1. Configure wan6

Open:

Network -> Interfaces -> wan6

Set these in General Settings and Advanced Settings:

Field	Value
Protocol	DHCPv6 client
Request IPv6-address	try
Request IPv6-prefix	auto
Extend prefix	disabled
IPv6 assignment length	64
IPv6 suffix	eui64

Then open DHCP Server -> IPv6 Settings:

Field	Value
Designated master	enabled
RA-Service	disabled / 無効
DHCPv6-Service	relay / リレーモード
NDP-Proxy	disabled / 無効

2. Configure lan

Open:

Network -> Interfaces -> lan

Set these in Advanced Settings:

Field	Value
IPv6 assignment length	64
IPv6 assignment hint	1

Then open DHCP Server -> IPv6 Settings:

Field	Value
RA-Service	server / サーバーモード
DHCPv6-Service	server / サーバーモード
NDP-Proxy	disabled
Always announce default router	enabled or forced, if LuCI shows it
RA offlink	enabled
RA SLAAC	enabled
RA Flags	managed-config and other-config

Save and apply, then restart wan6 and lan. Rebooting OpenWrt is also fine if you are unsure.

SLAAC / RA

Use this when wan6 has no IPv6 PD, but does have a global IPv6 address. This is common on フレッツ 光ネクスト without ひかり電話.

1. Configure wan6

Open:

Network -> Interfaces -> wan6

Set these in General Settings and Advanced Settings:

Field	Value
Protocol	DHCPv6 client
Request IPv6-address	try
Request IPv6-prefix	empty
Extend prefix	enabled (※1)

※1: In OpenWrt versions prior to 23.05, this option may not be visible in LuCI. If missing, run uci set network.wan6.extendprefix='1' && uci commit network && /etc/init.d/network restart via SSH. | IPv6 assignment length | empty |

Then open DHCP Server -> IPv6 Settings:

Field	Value
Designated master	enabled
RA-Service	relay / リレーモード
DHCPv6-Service	disabled / 無効
NDP-Proxy	relay / リレーモード
Learn routes	enabled

2. Configure lan

Open:

Network -> Interfaces -> lan

Set these in Advanced Settings:

Field	Value
Delegate IPv6 prefixes	enabled
IPv6 assignment length	64

Then open DHCP Server -> IPv6 Settings:

Field	Value
RA-Service	server / サーバーモード
DHCPv6-Service	server / サーバーモード
NDP-Proxy	relay / リレーモード

Then open DHCP Server -> DHCPv6 Settings and set the following:

Field	Value
DHCPv6-PD	disabled

Then open DHCP Server -> IPv6 RA Settings and set the following:

Field	Value
デフォルト ルーター	強制
SLAAC の有効化	enabled
RA フラグ	managed config (M) and other config (O)

Save and apply, then restart wan6 and lan. Rebooting OpenWrt is also fine if you are unsure.

Completion check

Confirm these points:

1. wan6 status shows IPv6 address.
2. On DHCPv6-PD lines, wan6 also shows IPv6 PD.
3. A LAN-side PC or phone receives an IPv6 address and can reach the network.

By following this tutorial, both the OpenWrt ULA (Unique Local Address) and FLET’S global IPv6 addresses can coexist, whether in SLAAC or PD mode.

This page only handles LAN-side IPv6. After this, return to Classic Setup Flow and create the Flet'H IPoE interface.