THX for your answer. I didn't say something to the loopback Interface, because without this interface the problem is the same.
So my problem have nothing to do with the loopback interface card.
So i will also explain somthing to the loopback interface. You can add to a physical networkcard another interface. This is an
virtual networkinteface. On a linux machine the card is eth0:1. When you have installed this type it is nothing different to a server
system where you installed 2 physical interfaces.
When the system have 2 network interface you can setup a public interface with the default gw to connect to the lan or wan and
you can also configure the second card to connect to an internal network to connect to some other Server Systems or NAS Storage.
The only thing is, that the both interface cards is on a different network.
So but my problem is also not fixed with the only one interface. And why did the manual backup work fine and the automatic backup
failed? This is the question.
So proberly someone have a idea to fixed my problem.