Windows Authentication fails with AWS Application ELB

While configuring an AWS Elastic Load Balancer for a customer I came across a strange issue related to Windows Authentication. Going through an internal application load balancer configured with HTTP listener, the target web server (IIS) constantly prompted for credentials and would not accept the correct ones, causing logon issues and even connections to other users’ sessions. After some investigation, I created a new network load balancer instead of the application load balancer used initially and it started working.

 

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