We have an Exchange 2013 Environment running on Server 2012 R1.

We currently have two MBX Servers in a DAG, and only one CAS.

I want to add a second CAS for redundancy.  The current CAS is on Cumulative Update 5.

Questions:

1.  Can I install CAS2 with CU7 and add to Exchange, or do I need to update CAS1 to CU7 first?

2.  When I upgrade CAS1 to CU7 - how much downtime will there be?

well in Exchange 2013 CU updates does not need to be same.

if you want you can install the 2nd CAS with CU5 and then upgrade each server one by one

since there is no CAS Array you should be good to go

Hi BCT-Tech,

1. Yes, you can install CAS2 with CU7 directly and add to exchange.

2. If you use high availability for two CAS servers, there will be no downtime.

I recommend you refer to the following articles to understand Exchange 2013 CAS high availability :

Load balancing

Exchange Server 2013 Client Access Server High Availability

Best regards,

OK, I added the CAS02 Server and installed the SSL.

CAS01 was already set for all internal & external names to be mail.server.com

On CAS02, I configured all internal & external names to match, and created a second DNS A Record for mail.server.com and pointed it to CAS02.

Now, when I launch Outlook on a new profile, I get the error "The server is unavailable".

Hi BCT-Tech,

Could you login in mailbox through https://CAS02/OWA ?

In addition, if you use the FQDN of cas02, could you create profile via outlook?

Best regards,

Some users started having trouble with email, so I took the DNS A record out for CAS02. I also realized that I had not added all the receive connectors that CAS01 had, so I did that.

Yes, I can login to OWA via https://cas02/OWA.

If I try to configure an Outlook profile with cas02.domain.pri then I get the error: "Outlook cannot log on. Verify you are connected to the network and are using the proper server and mailbox name. The connection to the Microsoft Exchange is Unavailable. Outlook must be online or connected to complete this action."

Also, when I run: "Get-ClientAccessServer | Get-OutlookAnywhere | select identity,*hostname" from CAS01 I get both Servers listed with internal and external names = mail.domain.com

When I run the same command on CAS02 I get:

"The operation couldn't be performed because object 'MBX01.domain.pri\CAS01' couldn't be found on
'DC01.domain.pri'.
    + CategoryInfo          : NotSpecified: (:) [Get-OutlookAnywhere], ManagementObjectNotFoundException
    + FullyQualifiedErrorId : [Server=MBX01,RequestId=4655cbf5-1fff-427a-89f7-33931ca03d33,TimeStamp=3/5/2015 4:48
   :10 PM] [FailureCategory=Cmdlet-ManagementObjectNotFoundException] 970BB837,Microsoft.Exchange.Management.SystemCo
  nfigurationTasks.GetRpcHttp
    + PSComputerName        : cas02.domain.pri