Hi @Mariusz_Kapuscinski, @Grzegorz_Gromadzki,
What service providers do you each have? The team will do our very best to provide workarounds for carrier-grade NAT that don’t involve requesting a routable/public IPv4 address for an additional cost from your ISP. We also recognize that these IPv4 addresses aren’t always available, affordable, or even a solution for the particular implementation your ISP has offered.
I empathize with your frustration. The reality is that the initial release of Roon ARC is not yet fully adapted to the near-endless variety inherent to global service provider architecture, and while it has been designed to work for the majority of internet service providers in most countries, it won’t work for everyone right away. Many will inevitably be arrested at the stage you find yourself in now as service providers and Roon independently investigate workarounds.
Rest assured that the team is investigating common denominator solutions for IPv6 that will eliminate the need to parse through the particulars of each ISP’s architecture, implementation, and contracts.
In the meantime, if you’re willing, the tech support team is standing by to assist in verifying that the double NAT layer isn’t somewhere in your local network, and to investigate other router-level causes for port forwarding issues.