Changes in Exchange 2013 CU5 target OAB, hybrid Exchange

Microsoft's update for Exchange 2013 includes changes to OAB generation and its popular configuration wizard.

Microsoft released Cumulative Update 5 for Exchange 2013 and Update Rollup 6 for Exchange 2010. Exchange 2013 CU5 is the successor to Service Pack 1, also known as Cumulative Update 4. At first glance, the update appears to be nothing more than a collection of fixes. However, Microsoft made some changes under the hood, specifically to how Offline Address Books are generated and to the Hybrid Configuration Wizard.

OAB improvements

Exchange 2013 CU5 includes changes to how Offline Address Books (OABs) are generated, according to a Microsoft blog. After the update, only a single OAB Generation Mailbox can generate an address list; multiple mailboxes could generate it before. The problem with that is that when Outlook clients connected to a different OAB Generation Mailbox, they would download the entire OAB again, instead of downloading only incremental changes. This was because each OAB Generation Mailbox would craft a copy of the OAB with a unique GUID. Since the GUID would change whenever a client connected to a different mailbox, an OAB download was triggered. This could cause a significant overhead on the network traffic, especially in larger environments.

Hybrid Configuration Wizard changes

It's not too surprising to see regular improvements to the Hybrid Configuration Wizard. Hybrid deployments are very popular and Microsoft regularly releases new features to support them. Exchange 2013 CU5 consolidates these new features by handling the configuration. Because of this, the Hybrid Configuration Wizard also configures the MRS Proxy on the Exchange Web Services Virtual Directory and manages oAuth configuration.

Additionally, when you run the Hybrid Configuration Wizard, you will notice there's a new option (Figure 1).

new Hybrid Configuration Wizard optionFigure 1

This option refers to Chinese Office 365, a tenant hosted by 21Vianet. 21Vianet recently announced a partnership with Microsoft to offer Office 365 in China.

Deploying Exchange 2013 CU5

Installing CU5 is no different from installing earlier versions. However, you might want to disable a specific Managed Availability probe after deploying it. Currently, there's a probe that automatically restarts a newly added service called the Microsoft Exchange Shared Cache Service. This service isn't currently used (it's planned for future releases), so there's little to no impact. However, if you don't like your event logs piling up with events from this probe, you can disable the probe and prevent all the alerts.

Schema updates

Cumulative Update 5 also introduces a number of changes to Active Directory. As such, you will be required to update the Active Directory schema before or with the installation of CU5.

Exchange 2010 Update Rollup 6

Next to CU5 for Exchange 2013, Microsoft also published Update Rollup 6 for Exchange 2010. This rollup update doesn't include any major functionality changes, but it does contains a myriad fixes. More information on Rollup 6 is available on its download page.

About the author:
Michael Van Horenbeeck is a technology consultant, Microsoft Certified Trainer and Exchange MVP from Belgium, mainly working with Exchange Server, Office 365, Active Directory and a bit of Lync. He has been active in the industry for 12 years and is a frequent blogger, a member of the Belgian Unified Communications User Group Pro-Exchange and a regular contributor to The UC Architects podcast.

This was first published in May 2014

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