Hi @Andreas_Nickel,
I understand it’s been some time since your initial post, so please accept my apologies on behalf of the team, as well as my thanks for your deep well of patience.
Per @Joost_Hoogland’s advice, you’re likely going to have to configure this Fritz!Box in Bridge Mode, IP Passthrough, or equivalent.
For a brief summary of how to set a manual port forwarding rule on a Fritz!Box modem/router with a second router, I recommend skimming this thread: Port Forwarding Instructions for (Most) Fritz!Box Users - #2 by connor
Essentially, you need to try the following:
- Check if your modem (Fritz!Box) is in
Bridgemode - Try to manually open the port in your downstream router’s (the Netgear’s) port forwarding configuration
- Make sure the IP/Port matches the Port listed in Roon → Settings → ARC
- Check for any VPNs or Firewalls that might be interfering
If these steps don’t work, please supply the following information to the support team, and we’ll work with you to pinpoint the issue or follow up with your internet service provider:
- What is the make and model of your modem and router?
- Do you have any additional network hardware, like additional routers or managed switches?
- Who is your internet service provider and what is your geographic region?
- Is your Modem configured in Bridge Mode so that it operates only as a modem or do you have the ports forwarded on both?