While testing a ADFS server for a customer from the internet to check if it was correctly published with ARR (IIS Application Request Routing)
The following Error occured:
First it looked that the URL rewriting rules on the ARR server where misconfigured.
Internally there was no issue and ADFS was working.
After checking if the the ADFS server could be reached from the ARR server it could not be reached. So the first step was if the ADFS server was placed in the hostfile.
This was not the case, so an entry was made in the hostfile and the ADFS server could be reached, but still error 502 occured from the internet.
In ARR the server was published with it’s IP address
After changing ARR to use the fully qualified domain name of the ADFS server the error was solved