Hi @Andreas_Wistuba,
Please accept my apologies that I’d initially missed your message. The support team would be happy to provide assistance.
Other users with Deutsche Telekom have successfully enabled port forwarding via auto-configuration. If that’s initially failed for you, then there’s likely an easily-resolvable issue with UPnP or multiple layers of network address translation on your home network.
Looking through diagnostics on your account, it’s possible the modem/router combination you’re using is incorrectly configured. What are the settings in your modem port forwarding administration page? Be sure to obscure your IP address if sharing.
I recommend you look at this threads that have solved the issue for users in your situation:
Port Forwarding Instructions for (Most) Fritz!Box Users
A dynamic IPv4 address won’t necessarily block port forwarding, depending on the ISP’s implementation. However, you need to make sure you have a public IP that Roon/ARC can access, and that there’s not an additional layer of network address translation preventing ARC or your Core from pointing at one another. You may need to request a public IPv4 address - often available as a static public IPv4 - from Deutsche Telekom. You can pass along the following specific questions:
- Have you implemented carrier-grade NAT for my account level?
- Have you fully implemented IPv6, or do you have IPv4 addresses available?
- Can I request a static IPv4 address to support port forwarding?
- Are there any ports you have reserved at the ISP level I should be aware of?