IPv6: Works for LAN clients - does not work for FW host

[tkaefer]

Hi there,

If tried to find a similar issue in the forum but I've haven't found the exact one, therefore I'm creating this one here.

I am using OPNsense on a German (vodafone) Cable Internet connection (with both IPv4 and IPv6 connectivity), using a Technicolor TC4400 (with Docsis 3.1).
IPv4 works like charme - no issue here.

IPv6 however is a bit finicky.
I does (normally) work for the clients within LAN.
On the OPNsense FW host (dedicated hardware, no VM) however, I
it sometimes works, but mostly it doesn't.

Strangely enough, I do get assigned two IPv6 IPs, one prefix and one IPv6 within the prefix - all on the WAN interface.
The two IPv6 IPs are not in the range of the prefix.

All clients in the LAN get IPv6 IPs within the assigned (from vodafone) prefix.

Using ping6 with any of the WAN IPv6 IPs fails, but using the IPv6 assigned to the LAN interface on the FW host works.

I've tried adding, removing routes, removing IPs from the WAN interface etc.
I've tried quite some things found by Google and co. - none of them brought me any solution.

I' am a bit stuck now. Are there any hints how to solve that?

[tiermutter]

Almost the same in this thread: https://forum.opnsense.org/index.php?topic=27548.0
It´s Vodafone again, the third case...

[tkaefer]

Almost the same in this thread: https://forum.opnsense.org/index.php?topic=27548.0
It´s Vodafone again, the third case...

Thanks for pointing it out (strangely I've missed it) - seems pretty familiar.

More than one IPv6 IP assigned and some of them are not in the assigned prefix.