CAS Array Network Load Balancing Issues causing Outlook Login Pop-Ups


  • Hi Folks:


    I have a CAS Array in an Exchange 2010 DAG enviroment (non SP1). We are having issues with the Network Load Balancing when both CAS1 and CAS2 are "converged" causing Outlook Login Pop-Ups for end users. In order to fix this issue temporairly, I had to disable one of two CAS servers windows NLB. Very starnge..can't figure out the problem..any help will be greatly appreciated.

    Monday, August 15, 2011 12:00 AM


  • Luis,

    One time in one the biggest Exchange Implementation, I did for one customer, we were continiously facing the same problem on a random client machines, that suddenly Outlook drops the session, and request to enter the user name and password, and later on while working on this case, we found that it was a performance problem, which cased RPC Dialogbox on client end.

    Check the performance monitor on your side, and I also seen sometime, there is a virus (confliker) on the client end, which causes the denial of service attack on DCs, so when the user initiate truck loads of request for DC, so eventually OUTLOOK drops the session.

    Zahir Hussain Shah | Senior Infrastructure Consultant - Messaging | My blog: | [Info: If you see my answer, fixes your problem, please mark my reply as "Answer", so I can help others.
    Tuesday, August 16, 2011 7:24 AM
  • It seems RPC issue going on for one server. Colud you post the error message from Outlook which may us help in depth.

    When the issue appears what was the RPC usage status for the affected server ?


    Mihir Nayak
    Tuesday, August 16, 2011 7:47 AM
  • Hello Luis

    This is a Known Issue - try to ping the NLB IP from a External System & in about 30 min you will find packet drops starting
    As far as my knowledge there is no known fix for this 

    Syed MM - MCTS: Microsoft Exchange Server 2007/2010 || MCSE || MCSA ||
    Tuesday, August 16, 2011 8:29 AM

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