Saturday, March 4, 2017

How to configure Exchange 2010 Client Access Carry?

Before we continue and configuring Exchange CAS Array, I think we need to understand how and what type of connection is handled by the CAS servers and accordingly we can plan for the configurations.

In Exchange 2003, 2007 we had Frond end and Backend concepts were as Outlook Web Access, Outlook Anywhere, Active-Sync and other web services connected to CAS/Front End servers and MAPI/RPC connections connected directly to Backend mailbox servers.

Continue from Exchange 2007, we have CAS servers in Exchange 2010 but it’s improved lot of architecture design level.

MAPI/RPC, Outlook Anywhere, Outlook Web Access, Outlook Web Services, Active-Sync..etc is connecting to Exchange 2010 Client Access Service. However, still, Public Folder connection still routed to Backend Mailbox Server directly.

Benefits of CAS Arrays: -

It improved the common namespace connection from outlook and other resources.
It improved End user experience during the mailbox server/database failover.
Also, we can throttle the connection to improve the performance of the server.

Configuration: -

  • CAS Array is an object in Active Directory that associates with DNS name for RPC Client Access Service for a particular AD site.
  • Create the CAS Array Object in Active Directory.
  • Create DNS records for the CAS Array pointing the IP address of the CAS servers.
  • Configure the RPC Client Access Server attribute on the Mailbox Databases in the site.

Create the CAS Array Object in Active Directory: -

CAS Array objects are created and Managed using Exchange Management Shell, you cannot use Exchange Management Console to create and administer it.

  • Name = Headoffice or whichever is referred to your organization.
  • FQDN = or whichever is preferred for your organization.
  • Site =AD Site “HeadOffice” where your mailbox server is installed.

New-ClientAccessArray – Name “HeadOffice” –Fqdn 

“” –Site “Default-First-


Create DNS records for the CAS Array:-

In this port, I am using DNS Round Robin type, but you can use Hardware Load balancer, Windows Load Balancer.

Configure the RPC Client Access Server attribute on the Mailbox Databases: -

The Final step is to configure mailbox database RPCClientAccess server attribute. It is this attribute that Outlook looks up to determine which RPC Client Access Server to connect to for a given mailbox.

The attribute is set automatically when the mailbox database is created to either,

The CAS Array name if one already exists in the AD Site

The FQDN of a Client Access server in the AD Site

You can see from this that it is wise to configure the CAS Array object first before creating mailbox databases, or at the very least creating the CAS Array object and updating the mailbox databases before deploying mailbox users to those databases.

Get-MailboxDatabase | Set-MailboxDatabase -RpcClientAccessServer

High Availability for Exchange Client Access Array: -

One of the biggest benefits of CAS Array is that enables the RPC Client Access Service is made highly available during the Patching, Hardware issue.

Thanks for Visiting. Keep watch for the further updates!