IPv6 - weird interaction between opnsense and fritz!box

[julf]

The WAN interface of my opnsense box connects to my fritz!box fibre optic modem. Strangely the opnsense interface, configured for dhcp6 only gets a link-local address, while my laptop gets a proper global IPv6 address when connected directly to the fritz!box.

Any clues or suggestions? I might of course be doing something stupid...

[KHE]

Did you select Request only an IPv6 prefix in the DHCPv6 client configuration of the WAN interface?
If yes unselect it.

KH

[julf]

Thanks, that helped - now the WAN interface gets a proper, routeable address. Now I just need to get the same to happen with the clients on the LAN interface.

[KHE]

Set IPv6 Configuration Type to Track interface and in the Track IPv6 Interface section then select WAN. If you have only one internal network you can leave the IPv6 Prefix ID to 0 (Also needed if the Prefix is only /64).

KH

[julf]

That is what I have - and I have a /48. Looking at the dashboard, I see that the dhcp6 server is not running, and refuses to start. In the general log file I see a message with "found no suitable IPv6 address on em0".

[KHE]

Did you set something under Services -> Router Advertisements -> [LAN] -> Router Advertisements?
I use Unmanaged, which means SLAAC (Stateless Address Auto-Configuration).

I have not used DHCPv6, because SLAAC was easier for me to setup and also some devices (e.g. Android phones) seem not to work with it.
It is possible to set up a network with DHCPv6, but IPv6 is designed to work without it. There are many websites out there describing the reasons to use SLAAC or DHCPv6 and as many opinions which one is better.
IPv6 introduces many new concepts and solutions, and I just wanted to mention that SLAAC is the option which works for me.

I forgot to mention, that in the LAN interface I checked the Manual configuration checkbox.

KH
 

[julf]

I did try changing to SLAAC, but the client machines on the LAN still only have link-local addresses.

[KHE]

If a reboot does not work, then is time for screenshots of the WAN, LAN and Router advertisment settings.
There sometimes seems to be an issue with the propagation of the IPv6 prefix.

KH

[julf]

Will do that tomorrow morning - it is not entirely trivial, as the machine I use to access the opnsense box doesn't talk to the Internet...

[Greelan]

Is the /48 actually getting delegated to OPNsense? Check under Interfaces/Overview/WAN.

It is possible that the Fritz!box is taking the prefix. Some modems don’t bridge IPv6 properly, and so it is necessary to disable IPv6 entirely on them before bridging, so that they don’t interfere with OPNsense getting an IP address and prefix on the WAN interface.

[julf]

Hmm, yes... Interfaces/Overview/WAN shows that the OPNsense box only gets a /57.