I am implementing a High Availability Portal and Server (ArcGIS Enterprise 10.5.1). Portal has two machines and Server has two machines, each set of machines is behind a load balancer.
Portal x2 + web adaptors
ArcGIS Server x2 + web adaptors
If I set everything up using ArcGIS Portal authentication I can Federate and Host the Portals and Servers and everything works well.
When we configure web tier authentication and single-sign on (Active Directory) using Esri's provided instructions the system fails - specifically we get an unauthorized user error in the Federation window in Portal and when we try to access ArcGIS Server Manager we get an unauthorized user error message. Note, we can still get access to ArcGIS Server Administrator page using the siteadmin user / password.
If anyone has any ideas, it would be greatly appreciated.