I am currently setting up a PP 2017R2 server with LDAP connected authentication by using Kerberos on a RHEL 7 machine. Kerberos has been configured on the system and is working just fine (I can login with my AD accounts on the linux box).
In the Authentication/Security Settings of the Pipeline Pilot server I clicked Allow SPNEGO (Kerberos) and didn’t change any other settings.
 
I can now login to the Server with my pipeline Pilot Client with my AD credentials.
 
However, when I want to access the admin page for example (or whatever other web resource) I get a popup window asking me to authentify (screenshot attached)

I tried every possible login/pw local and AD account and nothing works. I can only click cancel and the popup disappears and then I can use the classical web login (shown below the popup) where authentication works.
I noticed that this popup only shows up when I activate the Kerberos Authentication in the PP admin page.
How can I get rid of this authentication Popup ?
 
Thanks in advance

Peter