Rewrite Rule: Question about regex pattern

Question

I can't figure out why a certain rewrite rule does not work. I have this rule:

<rule name="CanonicalHostNameRule1" enabled="true">
  <match url="(.*)" />
  <conditions>
    <add input="{HTTP_HOST}" pattern="testsite\.com" negate="true" />
  </conditions>
  <action type="Redirect" url="https://www.testsite.com/{R:1}" />
</rule>

When I go into IIS and using the URL Rewrite module, I tested using " http://testsite.com ". This works. But after placing an updated web.config in production, these are my results from typing in these into the url:

I was able to reach the site by typing in these variations:

https://www.testsite.com
http://www.testsite.com
www.testsite.com
testsite.com 

But I received the error message "testsite.com refused to connect" when typing in:

https://testsite.com
http://testsite.com

What am I missing, that is preventing the last 2 from working? It seems like the rewrite rule I have should catch all requests.

Thank you in advance!

Answer 1

My guess would be that for the last two examples, their {HTTP_HOST} will have no www which means that it will match your condition resulting in your negate attribute skipping your rule action.

I would recommend enabling IIS Failed Request Tracing in order to identify exactly why your rewrite rule isn't working for those values.