No VLANs. The 2 boxes share the same subnet. I have already tried disabling the bonding but without sucess.
What impact has changing the authentication method?
Is this only for user authentication or resolving hostnames as well?
With a hint from support I could find the problem.
I had some Users in our NIS with UID < 100 which were conflicting with the replication in some way.
As soon as I removed this users, the destination volume appeared in the replication task window.