OWA redirection/Proxying in Exchange 2013/2010

In the old coexistence scenario between Exchange servers e.g. (2003 and 2007) the OWA is configured through powershell with URL redirection but in the new Exchange 2010/2013 the OWA redirection happens with Proxying but this operation for me is very blurry as I can't understand the exact mechanism of how does Exchange 2013 know the urls of Exchange 2010 ? Where does it read it from and what does proxy exactly means from technical prospective?

I have had couple of issues with redirection and was not able to find out how to get around it, how to reconfigure it or fix issues when things go wrong. I would appreciate if someone could provide an article on this or tell me how things work with OWA in coexistence scenarios .

Thanks a lot
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Mohammed HamadaSenior IT ConsultantAsked:
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Manikandan NarayanswamySecurity Specialist & IBM Security GuardiumCommented:

For Exchange 2010 & for Exchange 2013. Please follow the below links for Proxying & Redirection which help you understand



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Will SzymkowskiSenior Solution ArchitectCommented:
When a user is in an Active Directory Site (remote office Site B) and their mailbox exist on another Exchange Server in another active directory (Site A) site the following process happens...

- The CAS server where the user is currently located (site B) will check and see where User1 mailbox reside
- It discovers that the mailbox does not reside in SiteB but it reside in Site A
- CAS Server in Site B will then check the ExternalURL for OWA in SIte A
- If the ExternalURL is Null or does not have anything configured the CAS server in Site B will proxy the connection to the CAS server in Site A
- If the ExternalURL is present on the CAS server in Site A, the CAS server in Site B will re-direct the user to the CAS server in Site A.

Redirection is much more efficient and it is recommended.

Take a look at the below link with has a good overview with Diagrams of how Proxying and Redirecting work.

Mohammed HamadaSenior IT ConsultantAuthor Commented:
Thanks a lot Will, I don't have multiple sites in most of my deployments and I would like to understand what happens if both Exchange servers are in the same site on the same AD. does redirection happen or still proxy from CAS on the Exchange 2013 to 2010 servers ?

Will SzymkowskiSenior Solution ArchitectCommented:
Basically the same concept applies when you have a single AD site with a co-existance between Exchange 2010 and 2013. Exchange 2013 should be the Internet facing CAS server. At this point Exchange will check where the users mailbox is and depending on the protocol the user is using to connect to their mailbox will determine How exchange 2013 makes the connection.

If they are using OWA or ActiveSync Exchange will first try and re-direct the request. If it cannot redirect the request it will then proxy the connection to Exchange 2010.

It is based off of what the ExternalURL is set to on the other CAS server which then determines if it will redirect or proxy the connection to the mailbox.

Mohammed HamadaSenior IT ConsultantAuthor Commented:
Thank you all for your answers
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