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    <pre>thanks for the answers.
The request/communication looks like this:

HTTP GET : <span class="hljs-tag"><span class="hljs-string"><a class="moz-txt-link-freetext" href="https://mysp.org/myapp">https://mysp.org/myapp</a>
<redirect to idp, with correct authn request + login@idp, idp returns an assertion to the acs:>
</span></span><span class="hljs-tag"><span class="hljs-string">HTTP POST: <a class="moz-txt-link-freetext" href="https://mysp.org/acs/Shibboleth.sso/SAML2/POST">https://mysp.org/acs/Shibboleth.sso/SAML2/POST</a>

and the answer is:
</span></span>
<span class="hljs-tag"><span class="hljs-string"><b><span class="http">HTTP/1.1 <span class="hljs-number">404</span> Not Found
</span></b><b><span class="http"><span class="hljs-attribute">Content-Type</span></span></b><span class="http">: text/html
</span><b><span class="http"><span class="hljs-attribute">Server</span></span></b><span class="http">: Microsoft-IIS/8.5
</span><b><span class="http"><span class="hljs-attribute">X-Powered-By</span></span></b><span class="http">: ASP.NET
</span><b><span class="http"><span class="hljs-attribute">Date</span></span></b><span class="http">: Sat, 09 Mar 2019 09:06:26 GMT
</span><b><span class="http"><span class="hljs-attribute">Content-Length</span></span></b><span class="http">: 1245

</span></span></span>
<span class="hljs-tag"><span class="hljs-string"><span class="http">Here are the configuration snippets:

</span></span></span>    <RequestMapper type="Native">
            <RequestMap encoding="URL" applicationId="default">
            <Host scheme="https" name="mysp.org" port="443">                
                <Path name="<b>myapp</b>" authType="shibboleth" requireSession="true" <b>applicationId="spacs"</b> />                
                <Path name=<b>"acs/Shibboleth.sso"</b> <b>applicationId="spacs"</b> />
                <Path name="secure" authType="shibboleth" requireSession="true" />
            </Host>
        </RequestMap>
    </RequestMapper>

    <ApplicationOverride <b>id="spacs"</b> entityID="urn:eiam.admin.ch:pep:testpep">
        <Sessions lifetime="28800" timeout="3600" 
                  checkAddress="false" 
                  <b>handlerURL="/acs/Shibboleth.sso"</b> >             
            <SSO entityID="urn:myidp.org:idp:testidp">SAML2</SSO>       
            <Logout>SAML2 Local</Logout>
            <LogoutInitiator type="Admin" Location="/Logout/Admin" acl="10.0.8.93 ::1" />
            <Handler type="MetadataGenerator" Location="/Metadata" signing="false"/>
            <Handler type="Status" Location="/Status"/>
            <Handler type="Session" Location="/Session" showAttributeValues="true"/>
            <Handler type="DiscoveryFeed" Location="/DiscoFeed"/>                                               
        </Sessions>    
     </ApplicationOverride>         
    </ApplicationDefaults>

So why does the SP think, that the request /acs/Shibboleth.sso/SAML2/POST/ is something that it should ignore?
I also tried to map the path for the status page <Path name="acs/Shibboleth.sso/Status" applicationId="spacs" /> directly: leads to HTTP 404 as well.

/Peter
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    <div class="moz-cite-prefix">Am 08.03.2019 um 22:35 schrieb Cantor,
      Scott:<br>
    </div>
    <blockquote type="cite"
      cite="mid:A874230E-0561-4CF9-A123-AC0B488A0B14@osu.edu">
      <pre class="moz-quote-pre" wrap="">On 3/8/19, 4:29 PM, "users on behalf of Aaron Howell" <a class="moz-txt-link-rfc2396E" href="mailto:users-bounces@shibboleth.netonbehalfofaaron.howell@deakin.edu.au"><users-bounces@shibboleth.net on behalf of aaron.howell@deakin.edu.au></a> wrote:

</pre>
      <blockquote type="cite">
        <pre class="moz-quote-pre" wrap="">From my reading of the docs - there is a connection between the <ApplicationOverride> handlerURL must be located 
with in the <RequestMap>’s <Path>
</pre>
      </blockquote>
      <pre class="moz-quote-pre" wrap="">
The handler path(s) must map to the same applicationId as the resources do, that's all.

A 404 is the usual error to get because if the SP doesn't think the request is to something it thinks is a handler for the applicationId that applied to the request, then it will ignore the request, and nothing else is going to respond to it, so you get a normal 404 from there being no path or file with that name.

-- Scott


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