KNX routing doesn't work, but KNX-tunneling work, how to troubleshoot?

I am a bit stumped here. How can i troubleshoot a problem like this? This doesn’t work (can’t connect to the interface:

 routing:
   local_ip: '192.168.1.39'

This works with the same hardware

tunneling:
    host: '192.168.1.39'
    port: 3671
    local_ip: '192.168.1.52

Routing seems to be a bit more robust to use, so i would like to use that if possible.

Never mind I didn’t understand i had to input the ip of home assistant, not the router, why is that anyway? What of you have more than 1 router?

A routing connection is not a direct but a multicast udp connection. All participating devices connect to the IP multicast group address 224.0.23.12 . Having multiple routers connected to the same knx area/line doesn’t really make sense.
We use the local_ip to select the interface that shall be used. Technically this is optional now, but I think HA doesn’t let us configure it this way.