Hello, the Fritz! Box there are a so called emergency IP with which you can always reach the box! But why does it only with the Fritz! Box? It's not like it would be due to the router address, we have a EasyBox 904 xDSL, but which is in the same IP range as our old Fritz! Box, it was, so we do not need to change the IP Config !
By Traceroute I have now found that is redirected to the IP address on the ISP, I use Fing app where you can see this as ISP Internet address!
When my friend with the Telekom Traceroute went on t-ipconnect.de and internet.vodafone.de at vodafone on! Directs the traceroute query the Fritz! Box because of the features and the EasyBox not because there is no return to the router and typically responds there this feature!