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The Reverse Proxy Series — Part 2: IIS as a reverse-proxy

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  • As I sit at night waiting for Donald Trump to walk into the server room at any moment (you’re fired) I found your fresh blog.  A tear came to my eye as I read out loud your every word, yelling “That’s IT!”

    But, have another dime.  I am still at the same point as where I started.  Adding to the HTTP Provider Proxy Mapping was something I have not done let alone seen.  It made no difference.  I get a logon screen, logon, poof I have a logon srceen with no errors on it.  (you can’t make this stuff up, it just happens)  I went to the link you threw about proxy mapping.  Good thing you know where it is, noobs like myself would never think to look here, heck I’m still a recovering EP6SP2 addict.  And I guess my way of working this problem reflects that.  I have an OSS out on my issue now and it has been tossed to UME support, so far no light at the end of the http tunnel.

    I see that the third part in you blog is how to make WAS play nice with the proxy.  If I give you another dime, will you post that next?

    I have:
    Win2k3 IIS6 LDAP is MSADS.  My users come in from the internet and all I can show them is a logon page.  Sad but, true.

    It’s late, screen is a blur, but I still love this stuff.


    • Hi David,

      Excellent comment, made me smile all the way through. Cross my fingers that you get beyond the logon page soon.

      Did you post about your problem on the SDN forums too?

      Keep us in the loop, Mark.
      P.S. How did you post here without leaving a user trace? Accident or nice hack?

      • You said>>P.S. How did you post here without leaving a user trace? Accident or nice hack?

        No Up to date documentation to leave one. 😉 So I would say accident.

          • As you know I’ve seen your SDN post… 🙂

            I had a thought — did you try to recreate this with a different reverse-proxy, like Apache? perhaps your problem is IIS related.

          • Nope, convinced problem is not IIS.  All it does it translate the info from port 80 to 50000 and maps out the server and sub directories.  The mappings are correct.
  • What I and alot of SAP customers are lookinf for is full reverse proxy functionality from SAP Web Dispatcher ….can SAP Web Dispatcher work as a reverse proxy (SAP documentation implies not) ???


  • both the blogs were really helpful in getting a good understanding of reverse proxy. Thanks for such nice blogs. I am waiting for the next blog in the series. I would be interested apache reverse proxy. Also if you can talk about getting the backend system data like BW reports out through the proxy in a browser–(https)–>reverseproxy–(http)–>portal–(http/https)BWsystem scenario. Also how will the proxy to be configured if i had an ITS between portal and r/3 system for webgui. 

  • Hi Alon,

    I can only repeat what others already said: Thanks for the very good Weblog.

    I found one additional step I had to configure on my reverse IisProxy on IIS6. Possibly others need to do so too. IIS 6 only allows 260 characters in an URL segment ( The portal generates some URLs though which are longer that that (at least up to EP 6.0 SP2). This results in IIS rejecting the URLs with HTTP 400 “Bad Request”. SAP note 734462 pointing to Microsoft Knowledge Base article 820129 solves the problem.

    Setting the registry DWORD “UrlSegmentMaxLength” under [HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\HTTP\Parameters] to the value 1024 did solve the issue.


  • Hello Alan, good documentation.
    I just want to know, in case we have problem on iisproxy, is there any guideline to bypass IISproxy but still getting to the normal portal page for user (i.e not login to the administrator page for port 50000 for instance).


    • IISProxy is no longer developed or supported by SAP. If you still want to use IIS you’ll need to find a 3rd party solution — googling for “iis reverse proxy” gives some results, but I’ve never tried any of them. In general it’s not enough to have a simple redirection you need something to manage the communication going back and forth. MS ISA Server can also be configured as a reverse-proxy if you prefer to stick to MS products.


  • Great blog, one question though, when I click on the link I cannot see any content of the blog other then link and comments below…..any reasons for this?