Exchange Server 2010 NTLM and reverse proxy issues when using Hardware Load Balancers on Client Access Servers

Posted on 2011-10-12
Last Modified: 2012-08-13

Does anyone know what can cause NTLM authentication issues when there are multiple authentication attempts to Client Access Servers attached to a hardware load balancer or multiple load balancers? This is mostly happening when an Outlook Client is trying to connect via Outlook Anywhere (RPC over HTTP), on re-authentication attempts, the user keeps getting prompted to enter in their Active Directory credentials. This only happens when the load balancer(s) is attached to the CAS server(s) and are in an array. When the load balancer(s) are not in the picture, NTLM authentication works fine. Any help would be appreciated. Thanks.
Question by:leporej092170
    LVL 14

    Expert Comment

    If the load balancers are configured for ssl offloading then you would need to add the certificate to the load balancers and modify the cas accordingly. Really need more info on the load balancer configuration to assist further.

    Author Comment

    SSL offloading is set up as well as a certificate on the load balancers. SSL is turned off within IIS on the CAS servers. Need anymore information?

    Author Comment

    Anyone out there?
    LVL 14

    Accepted Solution

    Go to the test site,

    Gotta be a problem with he load balancers really can't imagine the fault being with the cas.

    Author Closing Comment

    Thanks for the assistance.

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