IPv6 connectivity from LAN side not working

[dseven]

fe80 addresses are link-local. They're not supposed to get routed. It's actually interesting that OPNsense appears to be routing it outbound, if I'm reading what you're doing right.........

[MatheusPP]

fe80 addresses are link-local. They're not supposed to get routed. It's actually interesting that OPNsense appears to be routing it outbound, if I'm reading what you're doing right.........

I understand link-local address should not be routed, but cant they be used as a gateway of other routes?
Clients on the LAN are getting a default route to the link-local address of OPNsense, and it in turn has a default route to the link-local address of my ONU.
If I plug my windows machine directly on the router, I get these routes and IPv6 works as expected using the link-local as gateway:
ff00::/8                                   ::
fe80::[...]/128              ::
fe80::/64                                  ::
2804:[...]/128 ::
2804:[...]/128 ::
2804:[...]::/64                    ::
::/0                                       fe80::1

[dseven]

Yes, but a client on your LAN can't use a LLA to talk to the LLA of your ONU, because it'd have to route through OPNsense to get there.

[MatheusPP]

That would make sense if the original packet destination was indeed the ONU LLA, but it is only been routed using those.

I gave up on the firewall in front of my network for now, will be making a new setup to test this thing with less devices to narrow it down.

[stefan00]

Indeed I think OPNsense is not the root problem in your case. Dig deeper into the ONU and see if it can get a bigger prefix delegated down to OPNsense. I don't think (anyone?) proper IPv6 setup with only a /64 dynamic prefix received is possible.

From what I read there is a chance the ONU does not even support delegating networks down.

After you did your next setup and research, it would be great if you could post your findings here, maybe including our ONU model. It's always interesting to know.

Good luck