Exchange 2013 CU6 – Hybrid Configurations and Hardware Load Balancing…

Exchange 2013 CU6 was released at the end of August, and it’s fair to say it wasn’t Microsoft’s most elegant CU release ever. If you are already using a Hybrid Configuration, the following problems are faced after installation:

– You cannot use the On Premise Exchange Admin Center to create new Office 365 mailboxes, move mailboxes to Exchange Online, or create In-Place Archive mailboxes.

– You also cannot perform administration of Office 365 through the EAC, because when you click on the Office 365 management tab, it takes you to a marketing page for Office 365 rather than the 365 login page.

There has been a script released by Microsoft to fix this behaviour, which is available here: http://support.microsoft.com/kb/2997355/en-us

It’s lucky that this script is available, because Microsoft made some changes to Exchange Online in the last few weeks. These changes mean that if you now attempt to create or manage a Hybrid Configuration in Exchange 2013 CU5 or older, you will see the following error:

Subtask CheckPrereqs execution failed: Check Tenant Prerequisites

Deserialization fails due to one SerializationException: 

Microsoft.Exchange.Compliance.Serialization.Formatters.BlockedTypeException: The type to be (de)serialized is not allowed: Microsoft.Exchange.Data.Directory.DirectoryBackendType

This can be resolved by, you guessed it, upgrading to Exchange 2013 CU6. Just remember to run the script which I linked to above after installation!

Another problem which a colleague of mine witnessed a few days back was related to CU6 and CAS Load Balancing. If you use a hardware load balancer such as a Kemp or NetScaler, and you install CU6, you will need to make some configuration changes to your availability monitors. Application aware load balancers will monitor Exchange Server 2013 using the Default Web Site in IIS, and a design change has been made in CU6 which will cause the load balancer to mark the Exchange 2013 server as down.

If you attempt to access the Default Web Site of an Exchange 2013 CU6 CAS server, it will return a status 302 and redirect you to the OWA site. A load balancer will see this and mark the server as being down. To resolve this problem, configure your load balancer to monitor https://CASFQDN/protocol/healthcheck.htm. For example, to monitor OWA you would use https://CASFQDN/owa/healthcheck.htm. The KB for this issue is here: http://support.microsoft.com/kb/3002351

Exchange Server 2013 CU6 has been a bit of a box of tricks so far, but if you are about to modify or create a Hybrid Configuration, then you MUST upgrade in order to be successful. Hopefully this article will help you in your quest for Hybrid greatness!

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