We have a CAS array includes two CAS servers (CAS1 and CAS2). We are using Windows NLB to load balance CAS traffic. The FQDN for the CAS array is outlook.company.com. RpcClientAccessServer property of the mailbox database is set to outlook.company.com. Everything was working fine until we recently installed the third CAS server(CAS3). We only installed the CAS role on the new server but have not added it to the NLB yet. It is odd that some outlook clients were connecting to CAS3 and complaining cert error. Of course we haven't installed certs on the CAS3 yet. But my question is why outlook connects to CAS3. For my understanding, outlook gets the RpcClientAccessServer property(outlook.company.com) from mailbox DB and the client resolves outlook.company.com to the virtual IP of the NLB. It should connect to CAS1 or CAS2 since CAS3 is not in NLB yet. We are running Exchange 2010 SP3 RU8v2. Windows NLB is set to use unicast. Can anyone shed light on this ? Thanks in Advance !
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