I have not been able to find step by step directions for ArcGIS for Portal and Reverse Proxy which uses IIS as a server. I have a setup in place which mostly work but fails at one critical point. Here's the setup:
1) Reverse Proxy Server (Windows) with static IP address accessible from the outside (only ports 80/443 allowed in).
2) An internal machine ('GIS') which has ArcGIS for Portal and Server installed along with their respective Web Adaptors ('portal' and 'arcgis' respectively).
3) The Portal also has WebContextURL of like 'https://gis.mydomain.com/portal'
4) The RP server has a couple of URL Rewrite entries--basically, direct to Server Farm which has the 'GIS' machine.
5) A proper SSL certificate is install as gis.mydomain.com in the IIS of both the RP server and the 'GIS' server.
So far this setup works great: I am able to access all content from the outside, such as https://gis.mydomain.com/portal/home and Gallery etc. But clicking on the Signup link in the Portal home page generates a browser error: Too Many Redirects (Header of 302). So the header being passed backed from the internal machine is 302 instead of 200.
I don't know what's happening. Maybe some extra security comes in picture when the signup.html page is called?
*** Update: Reverse Proxy Rules Screen Cap Added in this Question***