No 6LOWPAN transfer for custom IP address


I am trying to make to boards communicate via 6LOWPAN. For that, I start the application once as server, which opens a UDP port, and once as a client, which sends a short message to the server. Please find my code (which is heavily based on the gnrc example) here:

The problem starts, when I want to set a private IPv6 address on the client and the server. It still works on native, but when I run it on my boards (samr21-xpro), nothing is received by the server. If I send the message to the server’s link local address, everything works fine as expected.

Can someone help me, what I am doing wrong?

Best wishes