Host Header Configured on Selected Site Does Not Resolve to an IP Address that is Assigned to the Local System.

I was recently performing an in-place upgrade from CRM 2015 to CRM 2016 when during the system checks I received the following warning:

Host Header "notCRM.domain.com" configured on selected site does not resolve to an IP address that is assigned to the local system. This conflict must be reconciled for CRM Server to function properly. 

The fact that it was giving me a host header that did not pertain to the CRM website was odd so I took a look at IIS. What I discovered was that there was another website setup in IIS on the CRM Server. And that site had the site ID of 1.

As I was the original installer of CRM for this deployment, I knew that this site wasn’t here when CRM was installed. CRM originally had the site ID of 1, not this other site. Somebody had been in here messing around and changed the site IDs manually. After asking enough questions, I learned who did this and why. To make a long story short, their site needed to have the ID of 1. CRM, on the other hand, does not care so I rolled with the punches and decided I would work around this rather than cause a fuss.

From what I could deduce about the error message, the CRM installer was being told to look at the IIS website that had an ID of 1 to perform the upgrade on. I decided to switch the CRM site back to the ID of 1. To do this, you must first change the other site’s ID to a number not in use (e.g. 3, in my case). To do this, go into the site’s advanced settings.

After the other site was changed, I reverted the CRM site back to 1 and reset IIS.

The upgrade wizard will need to be restarted for it to pick up the change but once you make it back to the system checks, the warning should be gone.

The upgrade succeeded without issue but we weren’t done just yet. Since the other site needed to have the ID of 1, I needed to revert changes to the site IDs which in itself isn’t complicated. What was not taken into account was a registry key in HKLM\Software\Microsoft\MSCRM called “website”.

This registry key indicates which website directory in IIS CRM is using. Since CRM is using the ID of 2, this key needed to be switched to “LM/W3SVC/2”. In case you have been wondering what the ID controls, it is just an identifier used in the directory name for trace files and log files. It’s nothing critical that will not let CRM operate as normal.

By now you are probably thinking “Why didn’t you change this key rather than switching the site IDs to resolve the warning message during the upgrade?!?!” Well... it didn’t occur to me until afterward I completed the upgrade. Hindsight is 20/20!