Exchange 2007 to Exchange 2013 Transition and Autodiscover

Hi

We are in process of transitioning from Exchange 2007 to Exchange 2013. Out Exchange 2007 infrastructure is as follows:

1. Standalone Exchange 2007 mailbox servers
2. Load Balanced CAS (HT co-located) servers using Hardware Load Balancers
3. All the internal URLs including Autodiscover point to VIP (Load Balancer IP)
4. We do not currently provide connectivity to Exchange from Internet except for ActiveSync protocol

My question is specific to Autodiscover service during the co-existence period, so:

1. When we have new Exchange 2013 CAS server added to AD site that already has Load Balanced CAS servers, does this new addition creates a new Autodiscover SCP for new Exchange 2013 servers?

My understanding is that every new CAS addition (irrespective of Exchange version creates a autodiscover SCP in AD). Also, when Outlook 2007 is installed on a domain joined workstation then the Outlook client will query Active Directory for the Autodiscover information. Active Directory will return a list of SCP’s and the Outlook client will automatically select the first SCP in this list. Using the information found in the SCP the Outlook client will contact the Client Access Server for its configuration information and the Outlook client will be configured automatically.

When we load balance the CAS servers, using PowerShell commands we change the Autodiscover SCP to point to VIP FQDN.

1. If it does creates a new Autodiscover SCP for CAS 2013 (which is not part of NLB), will the SCP selection of Outlook client be non-deterministic/random (as usual) and can pick up either Load Balanced CAS SCP or new Exchange 2013 SCP? Or what’s the behavior in this case.
2. If for example, Outlook client picks up and contacts Autodiscover SCP of new Exchange 2013 CAS server and all mailboxes are still on Exchange 2007 MBX servers, what will happen – a Proxy or a Redirection? Please detail this scenario.
3. Can a Exchange 2013 CAS serve Autodiscover requests for users whose mailboxes are hosted on Exchange 2007 or, does this request needs to be proxied/redirected to Exchange 2007 CAS/MBX role?
4. Is there anything like when we introduce a new Exchange 2013 CAS server to existing Exchange 2007 environment, the existing Autodiscover SCPs (whether they point to CAS FQDNs or VIP FQDN) are over-written to point to new Exchange 2013 CAS servers? So in effect, CAS 2013 will take over all the Autodiscover requests coming from clients – PLEASE CORRECT ME IF I’M WRONG.
5. Does changing the AutoDiscoverServiceInternalURi value to single value (https://autodiscover.domain.com/autodiscover/autodiscover.xml) for all the CAS servers (Exchange 2007 and Exchange 2013) can help in any scenario?

Please help by sharing your experience/views/ideas

Thanks

Taranjeet Singh

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