Cross-Site Silent Redirection in Exchange 2010 SP2

OWA Cross-Site Redirection is the new feature in Exchange Server 2010 Service Pack 2 (SP2).  Before we proceed, we should first know what redirection is. Redirection is the process of redirecting user’s mailbox request from one Internet-facing CAS in one Active Directory site to another Internet-facing CAS residing in the same site.

Exchange Serve 2010 SP1 OWA Redirection Types

In Exchange Server 2010 SP1, we have three types of redirection experience for OWA which is described as below:

ü  Manual Redirection

ü  Temporary Manual Redirection

ü  Legacy Silent Redirection

1.       Manual Redirection is performed when a CAS server redirect an OWA request to Exchange Server 2007 or Exchange Server 2010 CAS server located in a different Active Directory site. But this redirection will take place only when the target OWA virtual directory must have an ExternalURL configured. Users will see the below manual redirection message and by clicking on the link provided in that message, OWA request will be redirected to the target directory.

Use the following link to open this mailbox with the best performance:

                http://emea.learnmsexchange.com/owa

2.       Temporary Manual Redirection takes place when client’s web browser still has old DNS entries cache which (like during a datacenter activation switch back) is pointing them to the CAS infrastructure that no longer hosts the mailbox. In this scenario, CAS will check if the target CAS has a FailbackURL value for the OWA virtual directory. If this value exists, then CAS issues a temporary manual redirection page providing the FailbackURL link. If a FailbackURL link is not specified, CAS issues an error page asking users to close all browser session to remove the cookies.  Below temporary manual redirection message would appear to the users during datacenter activation switchback.

  

3.       Legacy Silent Redirection, where silent redirection is the process of telling user’s browser to redirect and connect to a specified link. As we know, Exchange Server 2010 doesn’t fetch mailbox data from legacy versions of Exchange like Exchange 2003/2007. Below actions are taken by the CAS depending upon target Exchange version:-

·         If the Exchange 2007 mailbox is in the same Active Directory Site as CAS2010, CAS2010 will silently redirect the session to the Exchange 2007 CAS.

·         If the Exchange 2007 mailbox is in another Internet-facing Active Directory Site, CAS2010 will manually redirect the user to the Exchange 2007 CAS.

·         If the Exchange 2007 mailbox is in a non-Internet-facing Active Directory site, CAS2010 will proxy the connection to the Exchange 2007 CAS.

·         If the mailbox is on an Exchange 2003 server, CAS2010 will silently redirect the session to a pre-defined URL.

As you can see below, legacy silent redirection is only used for same-site scenarios between an Exchange Server 2010 and legacy versions. Legacy silent redirection tells the browser to establish a connection to legacy CAS2007/FE2003 infrastructure. For successfully redirection to legacy versions, the following must be configured:-

·         To redirect Exchange 2003 mailboxes, the Exchange 2010 OWA virtual directory must have the Exchange2003URL populated.

·         To redirect to an Exchange 2007 CAS, the target Exchange 2007 OWA virtual directory must have the ExternalURL.

Cross-Site Silent Redirection in Exchange 2010 SP2

As we have seen above, users are told that they are using the wrong URL and enter their credentials twice which leads to sub-optimal experiences with manual redirection. Exchange Server 2010 SP2 has provided us the fourth redirection experience. As the name implies, this redirection performs silent redirection to CAS located in another Active Directory site, but within the same Exchange Organization, that have an OWA ExternalURL.

A new parameter, CrossSiteRedirectType has been created that is available with Set-OWAVirtualDirectory cmdlet to support Cross-Site Silent Redirection. This parameter supports two values, Manual and Silent. Cross-Site Silent Redirection is disabled by default which means Manual setting is enabled which would continuously perform manual redirection between CAS in different Active Directory sites, after you deploy Exchange Server 2010 SP2.

Cross-Site Silent Redirection can be enabled by setting the CrossSiteRedirectType to Silent on the Internet-facing CAS OWA virtual directories:-

Set-OWAVirtualDirectory -Identity "LearnMSExchange\owa (Default Web site)" -CrossSiteRedirectType Silent