I tried tcpdump only on both devices. I did ping from hrem154.nano.tudelft.nl to 10.9.9.9.
this request come in on the enp0s25 device while 10.9.9.9 should go out by the tun0
device. I can see echo requests marked on both devices marked hrem154.nano.tudelft.nl >
10.9.9.9, but nothing in the other direction.
If I ping to 10.9.9.9 on the machine itself I see traffic in 2 directions.
Jouk