Exchange 2013 Post CU6 Update and issue

Dear All,

I have below Environment:

2 Exchange server 2013 Mailbox Server with D.A.G

2 Exchange server 2013 CAS Server.

i planned to update above server from cu5 To Cu6.

I have succesfully updated mailbox servers to cu6 without any issues.

But i am facing one issue with CAS-Server update to cu6 .I have updated one CAS Server to cu6.But as soon as i shutdown the non-updated CAS server my outlook client is not connecting to updated client access server.

Before Update when i use to shutdown one cas server my outlook client use to connect to second cas server vice-versa.

please help me......