Am 01.11.2016 um 13:40 schrieb Steve Volumetric:

It sounds like you're describing some kind of traffic re-routing, like
in a hotel where it pushes you to the hotel's site first no matter what
so you can authenticate, then it changes your vlan to one with WWW
access.  I think it's called a radius server, but is that the situation
you're in?  You might need to tinker with your dns settings.

Yes, that is the situation - in hotels, hospitals etc. Do you know which
settings exactly have to be changed?
Thanks,
Bernd