Dear All,

I am starting the migration of Exchange 2010 2 servers (CAS/Mailbox) with DAG no CAS Array to Exchange 2013 with 2 servers CAS array and 2 Mailbox servers with DAG. I read on some blogs that no requirement of CAS array on Exchange 2013. My concern how to configure NLB on CAS servers for the client to connect.

Please guide and have any deployment guide for this, kindly share.

Thanks

Hi ,

As you said there is no use and meaning of having the cas array in exchange 2013 and also thanks a lot to Microsoft for introducing an single namespace facility in exchange 2013.

My suggestion and Microsoft recommendation should be to go with hardware load balancers for exchange 2013 rather than using the windows NLB and round robin method.

Why we need to go for HLB ?

Disadvantages of some load balancing methods :

Windows NLB :-

If you use Windows NLB then it can provide redundancy on server level failure and not on application level.

DNS round robin :-
In case if we use the windows round robin method for load balancing then it wouldn't provide server level and application level redundancy during the failures.At the Same time we need to manually adjust the DNS records during the server failure but on the client end dns caches will create the issues.

Configuring NLB for exchange 2013 : 

http://msexchangeguru.com/2013/08/14/windowsnlb/

NLB configurations for exchange 2010 and 2013 will be same.

Configuring round robin for exchange 2013 : 

http://exchangeserverpro.com/exchange-2013-client-access-server-high-availability/

Advisable method is to have the CAS and MBX roles on the same box if NLB not comes it to play.Because windows failover clustering and NLB cannot be configured on the same box.In exchange 2013 cas role is a stateless server role so there is no need to have that role on a separate box.

This another technet KB helps to understand this concern in more depth : https://technet.microsoft.com/en-us/library/jj898588%28v=exchg.150%29.aspx

In Exchange Server 2013, there are two primary types of serversthe Client Access server and the Mailbox server. The Client Access servers in Exchange 2013 serve as lightweight, stateless proxy servers, allowing clients to connect to Exchange 2013 Mailbox servers.

Moreover, while doing the migration from exchange 2010 to 2013, you can also look on this automated solution (http://www.exchangemailboxmigration.com/) to accomplish this task quickly in more secure manner.

There are 2 things you need to take care:

1. On the HLB, you just configure the HTTPS load distributed into the 2 CAS

2. On Exchange server, you need to set the hostname for Outlook Anywhere (this is the replacement of CAS array)

Set-OutlookAnywhere -Server <CAS> -InternalHostname <FQDN resolved to HLB IP>

Hi,

In Exchange 2013, there is no CAS array any more. In order to load balance CAS servers, you can use hardware load balancers.

Here is a related article for your reference.

https://technet.microsoft.com/en-us/library/jj898588(v=exchg.150).aspx

Best regards,