If OA is enabled before Exchange 2013 in multiple sites, and use same url oa.contoso.com and redirect oa url using network switch to local site cas server, will it work?

Thanks

Hi,

Do you please post more details about your question?

It works with same Outlook host name in Exchange 2010/2013 co-existence environment. If you are currently using Outlook Anywhere in your Exchange 2007 or 2010 environments, in order to allow your Exchange 2013 Client Access Server to proxy connections to your Exchange 2007/2010 servers, you must enable and configure Outlook Anywhere on all of the Exchange 2007/2010 CAS in your organization.  Make sure that when you enable Outlook Anywhere on the Client Access Server, choose NTLM for IIS authentication and Make sure that when you enable Outlook Anywhere on the Client Access Server, choose NTLM for IIS authentication.

Here's an blog about Client Connectivity in an Exchange 2013 Coexistence Environment, for your reference:
http://blogs.technet.com/b/exchange/archive/2014/03/12/client-connectivity-in-an-exchange-2013-coexistence-environment.aspx

Hello SMFabc;

Actually we need more details to can help you, at all if you ask about the redirection, as i know on the network level the redirection will be between IP's only not names.. for example if you need to redirect to URL oa.contoso.com, the requester must request by IP not by name in case you need to redirect by your network firewall.

So the redirection should be by IIS.

Hi,

You can look at setting up regional namespaces where the autodiscover response provides clients with a different external hostname for Outlook Anywhere that routes them to their local site. E.g. oa-lon.domain.com for London and oa-us.domain.com for US.

More information here: http://blogs.technet.com/b/exchange/archive/2014/02/28/namespace-planning-in-exchange-2013.aspx.

There's also the option to use a global load balancer to redirect clients to their local site. For this option, multiple namespaces are not required.

Thanks.

I mean oa.contoso.com has virtual ip and network switch redirect virtual ip to ip of exchange server in local site