Hi @jcs,
Thank you for the report. Deutsche Glasfaser has widely implemented carrier-grade network address translation (CG-NAT) for their IPv4 residential-tier account addresses.
This means traditional port forwarding won’t work, whether configured manually by port forwarding rules in your router or via the autoconfiguration tool in Roon (UPnP or NAT-PMP).
Your options here are twofold:
- The diagnostic snippet looks like your ISP offers IPv6. You can set your network to native IPv6 from RoonServer all the way through to your upstream router. Here’s UDM’s guide on how to set DHCPv6 and native IPv6.
- The second option is to install Tailscale (or similar) on both RoonServer and the phone. It’s a wireguard-based free VPN service that allows for peer-to-peer encrypted TCP connections over a virtual mesh network. There are threads in Tinkering Tailscale implementation with ARC to circumnavigate ISP CGNAT
We’ll stand by for your response. Thanks!