Thanks for your ideas. I now disconnected the 1GB ports and switched all to the 10GB ports. Seems to be the best idea. Using the 1GB as Fallback is not the best idea, because we use the 10GB as trunk.
We'll do some testing. I'm not very happy but adding a additional 10GB nic for managment traffic is very expensive, because we speak about several servers and not only a stand alone one.
Wolfgang