Have you ever wondered where this web service is or tried to go to IIS and look for a virutal directory called ResportServer? I did, but could not find it of course. As the RS server is also a SharePoint WFE (in sharepoint integrate mode), could it be a Managed Path defined in the sharepoint? No, it is not either. Then how could this url be resolved?
The answer is, this url is reserved in HTTY.sys, and SSRS 2008 is not using IIS any more, for more details see this post.
