IPv6 PD and IPv6 subnets

[Cristian_Ichim]

Hi everyone. I would like to describe you an issue that I am having on my homelab setup. But first things first, I need to describe the setup.

I have an OPNsense router as my main router. This router is connected to the ISP via fiber optic PPPoE for IPv4 and DHCPv6 for IPv6. To simplify things, I will refer to this router as "router A".

Connected to "router A" I have two other routers: one of them is an Asus Router running MerlinWRT and the other one is another OPNsense router. I will refer to the Asus Router as "router B" and I will refer to the second OPNsense router as "router C".

"Router A" has received a /60 IPv6 prefix from the ISP and has delegated two /63 IPv6 prefixes to "router B" and "router C" from the /60 pool that it has.

Connected to "router A" I have a Raspberry Pi and my Desktop PC.

Connected to "router B" I have my phone via WIFI.

Connected to "router C" I have a laptop.

All my devices, including the ones connected to "router B" and "router C" have public GUA IPv6 addresses.

If I am trying to reach my Raspberry Pi, which is connected to "router A" from my laptop, which is connected to "router C", using the IPv6 GUA of my Pi, I cannot do it, no type of communication is done between these two devices. However, if I try to access my Pi from outside my home, from the WAN the communication is established on the IPv6 GUA without any trouble.

If I connect my laptop to a VPN provider which offers IPv6 GUA, then my laptop can easily communicate with my Raspberry Pi on the IPv6 GUA.

What is the setup that I must do on my routers so that my laptop can communicate with my Raspberry Pi without the need of connecting it to the VPN provider?