IIS Reverse Proxy with same hostheader under condition on 2 internal frontend server

danielW

11/8/23, 12:33 PM

a reverse proxy should be simple i thought but i encountered a problem. i try to accomplish the following: ive 2 webfrontends (serverA, ServerB) which hosting a webapplication contoso.local. then ive a server which is a reverse proxy on iis (with ARR & URL Rewrite)

the reverse proxy should send all incoming requests of contoso.local to serverA

if path123 is in the url it should send the request to serverB

i need to preserve the hostheader

so i configured the following on the reverse proxy:

enabled the proxy in ARR
set preservehostheader via system.webServer/proxy"%windir%\system32\inetsrv\appcmd.exe set config -section:system.webServer/proxy -preserveHostHeader:true /commit:apphost
added a new website in iss which has contoso.local as hostheader

added 2 rules with the following config described in web.config of that website contoso.local:

     <rewrite>
     <outboundRules>
         <preConditions>
             <preCondition name="ResponseIsHtml1">
                 <add input="{RESPONSE_CONTENT_TYPE}" pattern="^text/html" />
             </preCondition>
         </preConditions>
     </outboundRules>
     <rules>
         <clear />
         <rule name="ReverseProxyInboundRule2" stopProcessing="true">
             <match url="^path123(.*)" />
             <conditions>
                 <add input="{CACHE_URL}" pattern="^(https?)://" />
             </conditions>
             <action type="Rewrite" url="{C:1}://serverB/{R:1}" />
         </rule>
         <rule name="ReverseProxyInboundRule1" stopProcessing="true">
             <match url="(.*)" />
             <conditions>
                 <add input="{CACHE_URL}" pattern="^(https?)://" />
             </conditions>
             <action type="Rewrite" url="{C:1}://serverA/{R:1}" />
         </rule>

     </rules>
 </rewrite>

now if i test, ill get to serverA always. am i missing anything or is there any wrong in my logic?

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Lex Li

11/8/23, 5:16 PM

Enable FRT https://learn.microsoft.com/en-us/iis/extensions/url-rewrite-module/using-failed-request-tracing-to-trace-rewrite-rules and you can see for yourself.

danielW

11/9/23, 11:54 AM

sadly there is no option for "rewrite" as tracing provider

danielW

11/9/23, 11:59 AM

ok, repaired the rewrite module installation and then it pops up

Elon Musk

I sit in a Tesla and translated this thread with Ai:

EN: IIS Reverse Proxy with same hostheader under condition on 2 internal frontend server

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