I'm trying to create a reverse proxy which will rewrite all requests to a particular URL to another server inside the DMZ. I got the setup and configuration working based on this article https://learn.iis.net/page.aspx/659/reverse-proxy-with-url-rewrite-v2-and-application-request-routing

So my basic setup is like this -

Base URL which should trigger rewrite - http://MySite/Custom?Data=123

Proxy URL - http://MyProxyServer/Service?Data=123

My problem is with the two BOLD keywords above! I just cannot seem to successfully rewrite all requests to new URL.

Explaining in detail -

When i use the following rule -

<rule name="ReverseProxy" stopProcessing="true">
   <match url="Custom/(.*)" />
   <action type="Rewrite" url="http://MyProxyServer/Service{R:1}" />

I get an 404 error saying http://MySite/Service not found!

Tracing using failed req logs, i can see the rules working perfectly (new url is created correctly) but eventually the request ends with 404 error.

Thing is, if i slightly tweak the rule, everything works fine.

Following rule works -

<rule name="ReverseProxy" stopProcessing="true">
   <match url="Service/(.*)" />
   <action type="Rewrite" url="http://MyProxyServer/Service{R:1}" />

But i have to change my base url to http://MySite/Service?Data=123 from http://MySite/Custom?Data=123

So is there a limitation with reverse proxy implementation in IIS 7 where we have to match the sub directory/virtual directory names between source and proxy or are my rules inadequate?


There is an undocumented issue with ARR / rewrite, where it cannot map subfolders. I am adding this for my reference and hoping it helps others

A workaround I have tried that seems to be effective, is to create a folder inside your source web application, add a web.config inside that folder with the rules pointing to the destination web application:

<?xml version="1.0" encoding="UTF-8"?>
                <rule name="ReverseProxyInboundRule1" stopProcessing="true">
                    <match url="(.*)" />
                    <action type="Rewrite" url="http://<<<TARGET_HOSTNAME>>>{R:1}" />
                        <set name="HTTP_X_ORIGINAL_ACCEPT_ENCODING" value="{HTTP_ACCEPT_ENCODING}" />
                        <set name="HTTP_ACCEPT_ENCODING" value="" />
                <rule name="RestoreAcceptEncoding" preCondition="RestoreAcceptEncoding">
                    <match serverVariable="HTTP_ACCEPT_ENCODING" pattern="^(.*)$" />
                    <action type="Rewrite" value="{HTTP_X_ORIGINAL_ACCEPT_ENCODING}" />
                    <preCondition name="RestoreAcceptEncoding">
                        <add input="{HTTP_X_ORIGINAL_ACCEPT_ENCODING}" pattern=".*" />

Also added instructions from https://blogs.msdn.microsoft.com/friis/2016/08/25/iis-with-url-rewrite-as-a-reverse-proxy-part-2-dealing-with-500-52-status-codes/ around GZIP

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