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Exchange 2010 ActiveSync over DAG failover

Our Exchange DAG environment is spread over two sites. We have a site in Sydney and another in Melbourne.

Sydney is our main office whereas all Exchange Databases are mounted.

Melbourne is used as a disaster recover site when Sydney is ever to go offline.
 
Melbourne and Sydney are connected over the WAN and both have separate external IP addresses.
 
mail.mycompany.com external DNS record points to Sydney
mail-r.mycompany external DNS record points to Melbourne
 
OWA, Smart Phone devices etc are configured to connect to Sydney at mail.mycompany.com
 
Question:

Is it possible to  configure Exchange so that if/when Exchange databases failover to Melbourne in DR then ActiveSync will still be available on iPhone and Android devices?

Thanks for your help
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the_omnific
Asked:
the_omnific
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1 Solution
 
jimmithakkarCommented:
Hi

Batter you can configured single external DNS record for Sydney and Melbourne but different TTL value for diff ip add.
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the_omnificAuthor Commented:
Can you provide me with information of how to configure this?
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Simon Butler (Sembee)ConsultantCommented:
DNS doesn't give you failover. Even changing TTL etc is not going to do anything.

If you want failover for external clients then you will need to put a load balancer in a third location. Then all clients point to the load balancer and it manages which one is available.

Simon.
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the_omnificAuthor Commented:
Hi Simon thanks for that, I didn't think TTL would help to be honest.
 
How do you think I can address the problem when Sydney is online and but mailboxes are mounted in Melbourne?

Melbourne Exchange is a member of the DAG but has a separate CAS.

When this happens, users connecting via OWA get a prompt as pictured. owaWhich is fine! But activesync doesn't work.
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the_omnificAuthor Commented:
In order to get ActiveSync working we need to manually change the server address on the iPhone devices.
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Simon Butler (Sembee)ConsultantCommented:
DAG only protects the databases, it doesn't do anything for the CAS functionality.
That is why a load balancer would normally be used.

Exchange 2010 can proxy the information, but that requires no external URL set on the server that is hosting the mailboxes.

The only other option apart from using a load balancer would be to have a very low TTL time on the external host name, and then in the event of a failover, manually changing it.

Simon.
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