ARR (Load Balancing Mode) only shows 404

Question

Preamble:

I have 3 windows 2016 vms with IIS

IIS04 - the ARR server (arr.mytestapp.com)
IIS10 - the 1st load balancing target (host1.mytestapp.internal)
IIS11 - the 2nd load balancing target (host2.mytestapp.internal)

From the ARR server, i can browse to both hosts (the app loads)

For the farm setup, i have added both servers and this URL test

http://arr.mytestapp.com/status.aspx
Response Match = [Online]

which tests successfully - both servers pass

The Issue

When i browse to the arr url, it gives me "HTTP Error 404. The requested resource is not found"

I've enabled failed request tracing rules, but cant see much in there that's obviously wrong. The rewrite rules are using the name of the farm... not sure if this is a problem

 <EventData>
  <Data Name="ContextId">{80000015-0001-FF00-B63F-84710C7967BB}</Data>
  <Data Name="Substitution">http://mytestapp.website/{R:0}</Data>
  <Data Name="RewriteURL">http://mytestapp.website/favicon.ico</Data>
  <Data Name="AppendQueryString">true</Data>
  <Data Name="LogRewrittenURL">false</Data>
 </EventData>
     
<EventData>
    <Data Name="ContextId">{80000015-0001-FF00-B63F-84710C7967BB}</Data>
    <Data Name="OldUrl">http://mytestapp.website/favicon.ico</Data>
    <Data Name="NewUrl">/favicon.ico</Data>
</EventData>

I'm guessing this has something to do with my URL Rewrite rule... but I'm stumped.

<rule name="ARR_mytestapp.website" enabled="true" patternSyntax="Wildcard" stopProcessing="true">
    <match url="*" />
    <action type="Rewrite" url="http://mytestapp.website/{R:0}" />
    <conditions>
       <add input="{HTTP_HOST}" pattern="*.mytestapp.com" />
       <add input="{HTTP_HOST}" pattern="api.mytestapp.com" negate="true" />
    </conditions>
</rule>

Any help would be greatly appreciated

i've made some progress. I disabled all the other sites on the server, and added a blank host name binding, and it worked. seems you can only have one site per target server ? — JediNitrate

JediNitrate JediNitrate · Accepted Answer · 2020-12-22T12:13:32

So, if you have multiple sites setup on the same server, you need to add the ARR servers host header into each web servers host headers. It appears that ARR preserves the host header of the original request.

so for my setup, I now have the following. This resolves the 404 error

Site Bindings ARR Server

arr.mytestapp.com

Web Host 1

host1.mytestapp.internal
arr.mytestapp.com

Web Host 2

host2.mytestapp.internal
arr.mytestapp.com

ARR (Load Balancing Mode) only shows 404

1 Answers