WAN Incoming IPv6 not routed to router neighbours

[vlastikcz]

Hello,
I have Asus RT-AC66U B1 with configured 6in4 tunnel, assigned /64 and enabled Router Adverisement. Both firewalls (v4 and v6) currently disabled.

Communication to IPv6 addresses from LAN works perfectly. LAN clients receive IPv6 addresses.

But I'm also running a server application on one of the IPv6 clients. From LAN, I can connect to the IPv6 server w/o any issues.

Hovewer when I try to connect from WAN, the packed ends on the router and loops forever. Looks like the router does not know about it's own subnet and IPv6 client. If I connect to the router console and try to ping to the destination from it, the connection from WAN magically starts working for a while (it probably discovers this neibourgh in this way).

I know some concepts of ND, RA, etc., but I'm not sure what's happening here and how to fix that on my Asus (other than running ping forever to keep the routing active).

Please, could someone direct me to the right direction?

Thank you.

 

[vlastikcz]

For future reference: It seems to be fixed by setting WAN IPv6 Prefix Length to /128, while keeping /64 as the LAN Prefix Length. I had both as /64 previously.