Our Current setup

We have two sites in

Site 1

1 x Exchange 2010 Mailbox server part of DAG

2 x CAS/HUB 2010 servers in windows NLB

1 x UM 2010 Server.

Site 2

1 x Exchange 2010 Mailbox server part of DAG

2 x CAS/HUB 2010 servers in windows NLB

1 x UM 2010 Server.

Every time the DAG failovers from Site1 to Site2 users need to restart Outlook to connect to the appropriate CAS NLB. The site link between Site1 and site2 is very reliable and stable.

I want to know if we can remove the Outlook Popup/Restart every time we failover the DAG. Is there a way to achieve this.

Exchange 2010 simply doesn't handle cross-site high-availability well.  I recommend you prevent cross-site failover by entering the following command.

Get-MailboxServer | Set-MailboxServer -DatabaseCopyAutoactivationPolicy IntrasiteOnly

Then I'd suggest you develop and test a procedure for a planned and unplanned site switchover and switch-back.

If you want high availability, I recommend you add a DAG member and database copy in each site.

Thanks Ed

Most of the DAG failovers we do are planned and we want to get rid of the popup saying Outlook needs to be restarted.

Isn't there any option  to just merge the 2 sites so that Outlook profile doesn't change the server name to the CAS NLB's

Sure, you can merge the sites in AD Sites and Services.  Do you have a load balancer that's capable of working with CAS servers in the two sites?

I can't really merge AD sites.

Isn't there any thing in the Exchange configuration which would make Outlook clients to use the Site 1 CAS NLB even when the DAG is failed over to Site2

Hi,

Which Exchange version are you used?
In previous version, Outlook 2007 and Outlook 2010 clients dont automatically pick up the value of RPCClientAccessserver when you change, you need to repair Outlook Profile to update new RPC endpoint.
For  Exchange 2010 SP2 RU3 and later, we can change the value of AllowCrossSiteRPCClientAccess to allow the cross-site RPC connectivity. More details about RPC Client Access Cross-Site Connectivity Changes, please refer to:
http://blogs.technet.com/b/exchange/archive/2012/05/30/rpc-client-access-cross-site-connectivity-changes.aspx

Thanks

Clients will use what they're told to use, and that's specified by:

Set-ClientAccessServer -AutodiscoverServiceInternalUri

Set-MailboxDatabase -RpcClientAccessServer

Set-WebServicesVirtualDirectory -InternalUrl -ExternalUrl

Set-OabVirtualDirectory -InternalUrl -ExternalUrl

Set all of these to use a Site 1 URL and that's where they'll go.