With Exchange 2013 Microsoft changed from a service pack and update rollup model of patching to a cumulative update model. This essentially means, that every time we install a cumulative update we are uninstalling and reinstalling Exchange with the new updates built in. We should use this as an excuse to make sure our backups are working and are valid.
We will want to start by downloading the desired CU from Microsoft. In my case I’m going to install CU3 fro Exchange 2016. You can get a full list of available versions here. I think it’s a good idea to do a quick search of forums and blogs to look for some potential issues that may arise by installing the CU in your environment.
Most cumulative updates will come with an AD schema update so it’s a good idea to plan on this change needing to take place with a CU install. The schema update from a server that has the AD tools installed run the following commands to update the Active Directory Schema. The account you use will need to have Enterprise and Schema admin permissions.
These commands can be run prior to running the actual Exchange upgrade or they can be left and the setup process of the first server upgrade will complete these tasks for you. I like to run them ahead of the upgrade as a preparation task, but it’s really up to you.
D:\CU3>setup.exe /PrepareSchema /IAcceptExchangeServerLicenseTerms
D:\CU3>setup.exe /PrepareAD /IAcceptExchangeServerLicenseTerms
The following command will only be needed if you have multiple domains in your forest. It will need to be run in each domain in the forest.
D:\CU3>setup.exe /PrepareDomain /IAcceptExchangeServerLicenseTerms
Once the AD Schema has been updated, we are ready to run the CU Install.
We should start by placing the server into maintenance mode. This will allow us to install the CU without disrupting any users. Once the server has been successfully put in maintenance mode, we need to open a CMD prompt as an administrator and run the following command from the folder that contains the CU installer.
D:\CU3>setup.exe /m:upgrade /IAcceptExchangeServerLicenseTerms
After the install finishes, you should check services and event logs to ensure things look correct. Once you have verified that the upgrade was successfully installed, you can take the server out of maintenance mode and continue to the rest of the servers in your environment following the same process.
If your environment contains multiple servers, the upgrade process will put you in a situation where severs are running different versions of Exchange. This is expected and is acceptable, but it is best practice to not run for extended periods of time in this configuration.