All of the IIS configuration required to host TeamCity, Stash and NuGetGallery on a single IIS server using IIS web farm and rewrite rules to route hostnames:80 to TomCat sites on their default ports. The file normally lives at: c:\windows\system32\inetsrv\config\applicationhost.config

applicationHost.config

<?xml version="1.0" encoding="UTF-8"?>
<configuration>
    <!--
    ...
    -->
    <system.applicationHost>
        <applicationPools>
            <add name="DefaultAppPool" />
            <add name="Classic .NET AppPool" managedRuntimeVersion="v2.0" managedPipelineMode="Classic" />
            <add name=".NET v2.0 Classic" managedRuntimeVersion="v2.0" managedPipelineMode="Classic" />
            <add name=".NET v2.0" managedRuntimeVersion="v2.0" />
            <add name=".NET v4.5 Classic" managedRuntimeVersion="v4.0" managedPipelineMode="Classic" />
            <add name=".NET v4.5" managedRuntimeVersion="v4.0" />
            <add name="nuget.some-domain.com" managedRuntimeVersion="v4.0" />
            <add name="teamcity.some-domain.com">
                <processModel identityType="SpecificUser" userName="some-domain\svc_teamcity" password="[enc:IISWASOnlyAesProvider:...=:enc]" />
            </add>
            <add name="stash.some-domain.com">
                <processModel identityType="SpecificUser" userName="some-domain\svc_stash" password="[enc:IISWASOnlyAesProvider:...=:enc]" />
            </add>
            <applicationPoolDefaults managedRuntimeVersion="v4.0">
                <processModel identityType="ApplicationPoolIdentity" />
            </applicationPoolDefaults>
        </applicationPools>
        <customMetadata />
        <listenerAdapters>
            <add name="http" />
        </listenerAdapters>
        <log>
            <centralBinaryLogFile enabled="true" directory="%SystemDrive%\inetpub\logs\LogFiles" />
            <centralW3CLogFile enabled="true" directory="%SystemDrive%\inetpub\logs\LogFiles" />
        </log>
        <sites>
            <site name="nuget.some-domain.com" id="1" serverAutoStart="true">
                <application path="/" applicationPool="nuget.some-domain.com">
                    <virtualDirectory path="/" physicalPath="D:\inetpub\nuget.some-domain.com" />
                </application>
                <bindings>
                    <binding protocol="http" bindingInformation="*:80:nuget.some-domain.com" />
                </bindings>
            </site>
            <site name="teamcity.some-domain.com" id="2" serverAutoStart="true">
                <application path="/" applicationPool="teamcity.some-domain.com">
                    <virtualDirectory path="/" physicalPath="d:\inetpub" />
                </application>
                <bindings>
                    <binding protocol="http" bindingInformation="*:80:teamcity.some-domain.com" />
                </bindings>
            </site>
            <site name="teamcity" id="3" serverAutoStart="true">
                <application path="/" applicationPool="teamcity.some-domain.com">
                    <virtualDirectory path="/" physicalPath="d:\inetpub" />
                </application>
                <bindings>
                    <binding protocol="http" bindingInformation="*:80:teamcity" />
                </bindings>
            </site>
            <site name="stash.some-domain.com" id="4" serverAutoStart="true">
                <application path="/" applicationPool="teamcity.some-domain.com">
                    <virtualDirectory path="/" physicalPath="d:\inetpub" />
                </application>
                <bindings>
                    <binding protocol="http" bindingInformation="*:80:stash.some-domain.com" />
                </bindings>
            </site>
            <site name="stash" id="5">
                <application path="/" applicationPool="teamcity.some-domain.com">
                    <virtualDirectory path="/" physicalPath="d:\inetpub" />
                </application>
                <bindings>
                    <binding protocol="http" bindingInformation="*:80:stash" />
                </bindings>
            </site>
            <siteDefaults>
                <logFile logFormat="W3C" directory="%SystemDrive%\inetpub\logs\LogFiles" />
                <traceFailedRequestsLogging directory="%SystemDrive%\inetpub\logs\FailedReqLogFiles" />
            </siteDefaults>
            <applicationDefaults applicationPool="DefaultAppPool" />
            <virtualDirectoryDefaults allowSubDirConfig="true" />
        </sites>

        <webLimits />
    </system.applicationHost>
    <system.webServer>
        <!--
        ...
        -->
        <rewrite>
            <globalRules>
                <rule name="ARR_TeamCity_loadbalance" patternSyntax="Wildcard" stopProcessing="true">
                    <match url="*" />
                    <action type="Rewrite" url="http://TeamCity/{R:0}" />
                    <conditions logicalGrouping="MatchAny">
                        <add input="{HTTP_HOST}" pattern="teamcity.some-domain.com" />
                        <add input="{HTTP_HOST}" pattern="teamcity" />
                    </conditions>
                </rule>
                <rule name="ARR_Stash_loadbalance" patternSyntax="Wildcard" stopProcessing="true">
                    <match url="*" />
                    <action type="Rewrite" url="http://Stash/{R:0}" />
                    <conditions logicalGrouping="MatchAny">
                        <add input="{HTTP_HOST}" pattern="stash.some-domain.com" />
                        <add input="{HTTP_HOST}" pattern="stash" />
                    </conditions>
                </rule>
            </globalRules>
            <outboundRules>
                <preConditions>
                    <preCondition name="ResponseIsHtml1">
                        <add input="{RESPONSE_CONTENT_TYPE}" pattern="^text/html" />
                    </preCondition>
                </preConditions>
            </outboundRules>
        </rewrite>
    </system.webServer>
    <webFarms>
        <webFarm name="TeamCity" enabled="true" adminUserName="" adminPassword="[enc:AesProvider:...=:enc]">
            <server address="teamcity-hostname.some-domain.com" enabled="true">
                <applicationRequestRouting httpPort="8111" />
            </server>
            <applicationRequestRouting>
                <loadBalancing algorithm="WeightedRoundRobin" />
                <protocol reverseRewriteHostInResponseHeaders="true" />
            </applicationRequestRouting>
        </webFarm>
        <webFarm name="Stash" enabled="true" adminUserName="" adminPassword="[enc:AesProvider:...=:enc]">
            <server address="stash-hostname.some-domain.com" enabled="true">
                <applicationRequestRouting httpPort="7990" />
            </server>
            <applicationRequestRouting>
                <loadBalancing algorithm="WeightedRoundRobin" />
                <protocol reverseRewriteHostInResponseHeaders="true" />
            </applicationRequestRouting>
        </webFarm>
        <applicationRequestRouting>
            <hostAffinityProviderList>
                <add name="Microsoft.Web.Arr.HostNameRoundRobin" />
                <add name="Microsoft.Web.Arr.HostNameMemory" />
            </hostAffinityProviderList>
        </applicationRequestRouting>
    </webFarms>
    <!--
    ...
    -->
</configuration>