Load balance OWA URL - is CAS Array needed?

Is it possible to have a load balancer serve to load balance the external URL to Outlook Web App, without having a CAS Array?
The CAS Array not pre-existing before I acquired it is a different story....

But I'm curious if I have two Exchange 2010 servers, both with Client Access Role, with Outlook Web App configured, I could have the external DNS point the OWA.Domain.com to a load balancer that directs to either CAS server, without having an actual Cas Array object?
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StuartTechnical Architect - CloudCommented:
A CAS array has nothing to do with OWA, it is just for making RPC Client Access resilient between two or more CAS servers. OWA is HTTP(S), it sounds like you have split DNS configured so presuming your certificate covers the namespace mail.domain.com you should be good to go. What load balancer are you using?

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StuartTechnical Architect - CloudCommented:
Jeff GloverSr. Systems AdministratorCommented:
Yes,you should have a Client Access Array. You do this so when you connect via RPC, your client knows what CAS server to go to. You can manually set it up but it is best to create the array with a FQDN (has to be a name on your Exchange Certificate) and then setting the RPCClientAccessServer attribute on each Mailbox database to use it. You can create a DNS record for the array name or use a name already going to your Load Balancer.
Without the array, if one CAS server goes down, you could have an outage.

Now, if you have no internal Outlook Clients, then disregard
garryshapeAuthor Commented:
Well the server I'm bringing down, while is a CAS, it really has no mailboxes on it that people connect to. However, it is the server that owa.domain.com is set on as the External URL for OWA. That address is what users have been setup with on their mobile devices to connect their mailbox.
But their mailboxes are on a different server that is not going offline. So my understanding is if their web browsers and mobile devices are pointing to owa.domain.com, then if I change the server that owa.domain.com points to, given IIS is running and the CAS server has OWA set on it and the SSL certificate is installed with the right details, then there shouldn't be any interruption.
My understanding is there'd only be interruption of the connecting user was trying to access their mailbox on the server that is offline.
StuartTechnical Architect - CloudCommented:
This would act then the same as a CAS failover, the users won't see an outage. Make sure your internal TTL is low or you flush DNS after the change
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