Co-Existence for Exchange 2003 and Exchange 2010 – Part I

In this article I will demonstrate coexistence for Microsoft Exchange Server 2003 and Exchange Server 2010.

First thing we have to change is the Exchange Server 2003 operation mode.

Exchange server 2003 operation mode must be set to Native mode to continue this coexistence.
You can do this by go to properties in Exchange System Manager.

Click Change Mode to change the operation mode.

Next requirement is Forest and Domain functional levels. Both forest and domain functional level are should be upgraded to Windows Server 2003.

Exchange Server 2003 has to be upgraded to Service Pack 2 to support coexistence with Exchange server 2010.
You can check the service pack level by accessing servers node in Exchange System Manager.

You can download Exchange Server 2003 SP2 from here.

Let’s check the service pack level now.

Suppress Link State Updates

Use Registry Editor to suppress propagation of minor link state updates between routing groups in Microsoft Exchange Server 2010 and Exchange Server 2003.
More details are available here.

Open Registry Editor.

• Locate HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\RESvc\Parameters.
• Right-click Parameters and select New | DWORD value. Name the new DWORD value SuppressStateChanges.
• Double-click SuppressStateChanges.
• In the Value data field, enter 1.

• Close Registry Editor, and then restart the SMTP service, the Microsoft Exchange Routing Engine service, and the Microsoft Exchange MTA Stacks services for the change to take effect.

Now we can start the Exchange Server 2010 installation.

During the installation you will be asking to choose the routing group connector.

After the installation check the newly created Exchange Administrative Group in Exchange 2003 System Manager.

Now I am creating two host records for access both Exchange 2003 and Exchange 2010 web mail.

See Part II and Part III from below Links.

Part II – Co-existence for Exchange Server 2003 and Exchange Server 2010

Part III – Co-existence for Exchange Server 2003 and Exchange Server 2010