Make an OpenThread Border Router behave properly in an IPv6-only environment (SLAAC, RA, GUA)

I have a LAN that uses IPv6 and have been trying to set up a border router. I have been reading the documentation but that exact deployment doesn't fit my purposes:

• It focuses on NAT64 and DNS64 (which I do not want)
• It sets an hostapd mechanism (which I do not need)
• It doesn't say how to properly set up IPv6 routes and ips (which I do pursue)

I have had moderate success by building the ot-br-posix and configuring the radvd daemon in the border router machine. With this, the OpenThread devices receive the RA and configure their SLAAC properly.

However, I have been unable to make routes work at the globally addressable prefix. I can do pings from the border router machine to fd::/8 addresses (mesh-local addresses from OT devices) but I am unable to figure out what is wrong with the GUA addresses. The IPv6 addressing documentation is not helping me.

I have been trying to use tcpdump on the border router machine, but it doesn't seem to be working. I don't know where things are going the wrong way.

Make sure you add an IPv6 prefix to the Thread network that is suitable for communicating with devices outside the Thread network. You can do this with using OT CLI commands:

> prefix add 2001:0db8:85a3::/64 paros
> netdata register

Note that the default fd00::/8 addresses are the Mesh Local Prefix and only allow communication within the Thread network.