Integrated Windows Authentication WCF Multiple Host Headers IIS 6 not working - wcf

Question

I have a asp.net 2.0 web site with WCF service hosted inside it running on .NET 3.5 framework. The website is setup with Integrated Windows Authentication only. The web server is IIS 6 with load balancing on Windows 2003 Sp2 (2 servers). I am unable to access the WCF service (.svc) using the full url (http://myqa2.abcdefg.com/trxn/WCFTrxnService.svc). Also note that the server is configured with multiple host headers. The website is protected by siteminder. Initially I was getting an error
This collection already contains an address with scheme http. There can be at most one address per scheme in this collection. Parameter name: item
So added the following config entry
<serviceHostingEnvironment>
<baseAddressPrefixFilters>
<clear/>
<add prefix="http://myqa2.abcdefg.com"/>
</baseAddressPrefixFilters>
</serviceHostingEnvironment>
That error went away, but now I am being prompted for login by the browser. For same website, I am able to access .aspx page. The login prompt is appearing only for .svc file.
Here is the binding / endpoint from config file that I am using.
<system.serviceModel>
<serviceHostingEnvironment>
<baseAddressPrefixFilters>
<clear/>
<add prefix="http://myqa2.abcdefg.com"/>
</baseAddressPrefixFilters>
</serviceHostingEnvironment>
<bindings>
<basicHttpBinding>
<binding name="IISIntegratedAuthBinding">
<security mode="TransportCredentialOnly">
<transport clientCredentialType="Windows"/>
</security>
</binding>
</basicHttpBinding>
</bindings>
<behaviors>
<serviceBehaviors>
<behavior name="TestWCFFromSL.Web.WCFTrxnServiceBehavior">
<serviceMetadata httpGetEnabled="true" httpGetUrl="http://myqa2.abcdefg.com/fmc/WCFNotesService.svc"/>
<serviceDebug includeExceptionDetailInFaults="false"/>
</behavior>
</serviceBehaviors>
</behaviors>
<services>
<service name="TestWCFFromSL.Web.WCFTrxnService" behaviorConfiguration="TestWCFFromSL.Web.WCFTrxnServiceBehavior">
<endpoint
address="http://myqa2.abcdefg.com/trxn/WCFTrxnService.svc"
binding="basicHttpBinding"
bindingConfiguration="IISIntegratedAuthBinding"
contract="TestWCFFromSL.Web.IWCFTrxnService" />
</service>
</services>
<!--<serviceHostingEnvironment multipleSiteBindingsEnabled="true"/>-->

Answer 1

if a website is protected by SiteMinder, WCF / SOAP calls don't work. But a different solution to this problem is working.
The URL myqa2.abcdefg.com/trxn/WCFTrxnService.svc is protected by SiteMinder, but
myqa2/trxn/WCFTrxnService.svc is not protected by siteminder, Looks like SiteMinder only protects FQDN (Fully Qualified Domain Names). So I configured the application to call WCF service using short url instead FQDN. I also had to use crossdomainpolicy because the application considers myqa2.abcdefg.com and myqa2 as 2 seperate domains.