Role of CAS server and RPCClientAccessServer property

Hi all,

I am bit confused with this property RPCClientAccessServer of a database. What I don't understand is why do we need this property on the database when client Outlook connections are already handled by CAS server/array in a particular site.

What I know is when Outlook is opened first time it will use Autodiscover service via SCP to locate CAS server and mailbox location.

If Outlook is already using Autodiscover to locate the CAS server and other settings then why do we need RPCClientAccessServer property on a database to specify MAPI endpoint?

Sorry but I am bit confused with this CAS array topic and would appreciate help. Especially if someone can advise me connection flow from client to CAS/MBX server. Thanks.

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Comments

jibbajabba

This attribute is set when you create a mailbox database automatically. However, it does not get updated when you for example change the CAS server, remove it or it is simply down. Or you start with a single CAS server but add a second one and create a CAS array. This attribute will have to be changed manually to reflect the change. Why this is static ? Only Microsoft knows

jeanathan

The CAS server will communicate with a mailbox server where the mailbox of your user is located. 1. You use autodiscover or manually configure the outlook client to communicate with the CAS server. This can be a CAS array address or just the name of a CAS server. 2. The RPCClientAccessServer property on the database of your user mailbox determines what fqdn for the CAS server you are communicate with in outlook to use for RPC connections. So you you may be in AD site 1 and use CAS01, but if the RPCClientAccessServer property is set to CAS05 in "Ad Site 5" then your client workstations outlook program will build RPC sessions to the CAS05 server. To recap initial contact for outlook is based on the AD site, but after that the CAS server contacted will communicate with the mailbox server where the database containing your user mailbox is located. This will return the fqdn of a CAS server or Hardware Load Balancer (Port 135 & 1025-65XXX) for the outlook client to actual use when communicating with your mailbox. If the value set makes your client pull traffic over a slow LAN link then you may have a design issue.

Claymoore

It's only 2.5 years too late, but the Exchange Team is finally getting around to fully explaining what the CASArray is and is not. I just love reading an article and finding out I have been doing some things wrong on every Exchange 2010 implementation.
Demystifying the CAS Array Object - Part 1 - Exchange Team Blog - Site Home - TechNet Blogs

Turns out the reason the CASArray exists is to automatically populate the RPCClientAccessServer property.

What a CASArray isn't:

A CAS array object does not load balance your traffic
A CAS array object does not service Autodiscover, OWA, ECP, EWS, IMAP, POP, or SMTP
A CAS array object's fqdn does not need to be part of your SSL certificate
A CAS array object should not be resolvable via DNS by external clients
A CAS array object should not be configured or changed after creating Exchange 2010 mailbox databases and moving mailboxes into the databases
A CAS array object should be configured even if you only have one CAS or a single multi-role server.