Exchange 2007 and 2013 - CAS NameSpace for Multiple Data Centers

Hi

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

1. 2 Data centers (DC 1 and DC 2). Both with active user population. Both have their own direct Internet Connectivity
2. Standalone Exchange 2007 mailbox servers in each data center
3. Load Balanced CAS (HT co-located) servers using Hardware Load Balancers in each data center
4. All the internal URLs including Autodiscover point to VIP (Load Balancer IP)
5. No access allowed from Internet except ActiveSync devices
6. Outlook anywhere is disabled in Exchange 2007 organization
7. Autodiscover is not currently published on Internet, but we have a plan to publish it now
8. Our Exchange organization hosts mailboxes that have different Primary SMTP Addresses – so we would need multiple ‘A’ records and SANs on SSL certificate for Autodiscover to be published – please specify if there’s a alternate / recommended solution for this.

We will be using separate Load Balancers for HA of Exchange 2013 CAS. Each data center will have a dedicated set of Load Balanced CAS.

DAGs will be used for HA as well as site resilience of mailbox roles. Single DAG will be configured for both data centers

We wish to allow Outlook Anywhere and ActiveSync (no OWA) from Internet for mailboxes on Exchange 2013. My questions are related to CAS NameSpace in our specific scenario:

1. Is it possible to have a single CAS Namespace for both the Data Centers?
2. If yes, I understand that Autodiscover entry point from Internet would be only one – Please correct me here. If this is the case how the request would be handled in case of single CAS namespace (i:e When it will hit the first data center, how outlook Anywhere and ActiveSync requests for users with mailboxes in other data centers be handles – Proxy / Redirection)?
3. In the Single NameSpace scenario do we need to populate External URLs (or only Internal URLs) on the CAS virtual directories in other data center OR the Internal URL configuration will suffice (as this data center will actually not be exposed to Internet in reality from CAS NameSpace perspective).
4.  If External URL configuration is required in second data center, what those External URL values would be – FQDN of VIP in this data center?

                 As per our understanding, if External URL property is configured on a CAS virtual    directory, it will be returned to the client and it means a redirection will happen – but as the other data center is not exposed, will the client fails to access the service?

5. In case of co-existence between Exchange 2007 and 2013, when we configure Exchange 2013 as Primary endpoint for all CAS requests (co-existence setup between E2K7 and E2K13), how will Exchange 2013 handleInternet requests for mailboxes on Exchange 2007 for the following Protocols:

1. ActiveSync
2. Outlook Anywhere
3. Outlook Web Access  

Will these be proxied or redirected to Exchange 2007 servers?

6. How Exchange 2013 will handle Intranet requests for mailboxes on Exchange 2007 for the following Protocols:

1. Outlook Anywhere
2. Outlook Web Access  

Will these be proxied or redirected to Exchange 2007 servers?

7. Since, the data centers are also providing Site Resilience services for each other, will there be an issue in the even DR in single CAS Namespace

Thanks

Taranjeet Singh

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