IIS Reverse Proxy How to fix the location header

[Rachel S]

Hi,

We have an IIS server running as a reverse proxy for terminology.hl7.org. Requests coming in with a host of terminology.hl7.org are redirected to an internal server at http://3.142.231.50/terminology.

If the request is for http://terminology.hl7.org/6.2.0, the server at 3.142.231.50 issues a redirect with a Location header of http://3.142.231.50/terminology/6.2.0/. IIS reprocesses this header to http://terminology.hl7.org/terminology/6.2.0/.

Any suggestions to tackle this?

[Ryaan J.]

You must strip the /terminology path from the rewritten Location header in IIS.

Use ARR and URL Rewrite with outbound rule.

1. Ensure Application Request Routing (ARR) is installed

• Open IIS Manager → Server node → "Application Request Routing Cache"
• Click "Server Proxy Settings"
• Check "Enable proxy"

2. Add an Outbound Rewrite Rule for the Location header

Go to the site (or server level if global):

• Open "URL Rewrite"
• Click "Outbound Rules"
• Add New Outbound Rule → Blank Rule

Implement this setting:

• Name: FixLocationHeader
• Precondition: Create new

Precondition:

• Name: IsResponseRedirect
• Condition input: {RESPONSE_STATUS}
• Check if input string: Matches the Pattern
• Pattern: 3\d{2}
  (Matches 301/302/307/308)

Outbound Rule Configuration:

• Matching scope: Response Headers
• Variable name: Location

Matching pattern:

http://3\.142\.231\.50/terminology/(.*)

Action type: Rewrite

Value: http://terminology.hl7.org/{R:1}

3. Apply and Restart IIS with iisreset

Test using : http://terminology.hl7.org/6.2.0

Backend redirects to: http://3.142.231.50/terminology/6.2.0/