IPv6 clarifications: ISP VLAN WAN, LAN prefixes with ip6class

x86 23.05.3, one WAN port, one LAN port.

eth1 is WAN, eth0 is LAN. eth0 has eth0.x 802.1q devices and interfaces are directly attached to those.

Looking to set up IPv6 - currently disabled on the WAN side - but the docs seem unclear in places, and I couldn't find answers searching:

  • Its my understanding that for a PPPoE connection like mine, I change wan to PPPoE protocol and leave wan6 as DHCPv6, but given I need to use VLAN100 for the ISP, do I change both wan and wan6 to use the eth1.100 device?

  • My ISP hands out a /56 static prefix. My interfaces are setup to use /64 and hints are set. Is the ip6class option necessary for the interfaces to use ISP-assigned prefixes?

    • The docs have an example, but in it one device uses the defaults, the other uses wan6 and it doesn't say what the behaviour is for the one using defaults except that it can use both ULA and wan6. Will it assign one from each? Will it assign only from wan6 if its present?


no, that only comes into play if you need to filter (out) different prefixes (e.g. mwan3 or VPN connections) for your VLANs.

With pppoe add option ipv6 '1' to the main wan section. The standard way is for the ISP to advertise that IPv6 is available during ppp negotiation. Then the startup scripts should spawn a wan_6 (not wan6) interface which uses DHCPv6 inside the ppp tunnel.

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What's the difference here to the 'auto' default behaviour?

Also the wiki says setting it to 1 uses wan6 while leaving it auto will spawn the wan_6 interface.

Ah, so if I have multiple WANs, got it.