When I look at your error message, the ip address which is shown at router_external_ip starts with 100. This for me suggest your ISP has implemented CGNAT.
The MultipleNatFound line in the diagnostic code means there is a second layer of network address translation in between your Core and ARC other than that provided by your FritzBox. We’ll need to find a way to bypass that address translation.
As mentioned, the external IP address suggests this extra layer of network address translation (NAT) is in the form of carrier-grade NAT, or CG-NAT, in which case you’ll need to reach out to your ISP’s support department to ask about a dedicated public IP address for port forwarding.
Since there’s a possibility your local network has an extra layer of NAT as well, please verify that you’ve enabled PPPoE passthrough on the FritzBox modem, and let us know if you’re using any VPNs or proxy servers in this setup.
We’ll keep an eye out for your response. Thank you!
First of all thank you a lot for your efforts and sorry for answering so late…
I am not sure if i undestand the connections between my provider for the internet and the provider for my smartphone. Here’s a screenshot from my router…
I have news here - I now called my internet provider 5 times.
At last the believed me an checked it - and yes - I had a fix IP but something changed an so I now got this nated ip. I should get an new fix ip the next 2 days - and the I hope everything get’s fine.
Thanks a lot - if the problem still persits I come back to you…