In an earlier article I have already pointed out that it is important to consider the NET dependencies of Exchange. In theory, all Exchange updates are cumulative, i.e. the current CU contains the complete installation files as well as all previous patches. The CU can therefore be used to perform a new installation or to update an existing installation. In theory, an Exchange 2013 RTM installation, for example, can also be updated directly to the current CU. However, this is only the case in theory, as there are dependencies on the NET Framework version used and supported.
Michel de Rooij has created a nice graphic for the dependencies of the NET Framework versions to the Exchange version, which clearly shows that intermediate steps are sometimes necessary when updating an old Exchange 2013 installation:
The problem is already clear in the graphic: An Exchange 2013 installation with CU4 cannot be updated directly to CU19 because CU4 does not support NET Framework 4.6.2. NET 4.6.2 is, however, a prerequisite for CU19.
The installation must therefore first be updated to CU15, then the NET Framework can be updated to NET 4.6.2 and only now can Exchange 2013 CU19 be installed. The next intermediate step is already waiting in the wings, as NET Framework 4.7.1 will be a prerequisite for future CUs (these dependencies also exist for Exchange 2016).
As far as the problem is concerned, the intermediate step via CU15 must currently be taken in order to bring an old Exchange 2013 installation up to date. The stumbling block lies in a completely different area:
Where to get the CU15?
Microsoft no longer offers the CU15 for Exchange 2013 directly as a download, the link to the old CU15 download leads nowhere and the update page only contains the note that there is already a newer update. There is already a sobering thread about this in Technet:
However, the answer is not very helpful at first: Contact Microsoft...
If you still have the CU15 somewhere on your hard disk, you should not delete it at the moment. You might need it again...
I took the liberty of sending a request to MS to find out if it is really necessary to contact support to get a download link to the CU15. As soon as I have an answer, I will update the article.
Update 02.01.2018
Here is the answer from MS Support to my request. I did not receive a download link for the CU15, but I did receive a workaround. However, the case is not yet closed and I will ask again in more detail and update the article here.
Update 04.01.2018
I tried the recommended workaround once. However, I only had an Exchange 2013 server without DAG to hand. I proceeded as follows:
- Alle Exchange Dienste gestoppt und auf Starttyp „Deaktiviert“ gestellt
- NET Framework 4.6.2 installed
- Server restarted
- Alle Exchange Dienste auf Starttyp „Automatisch“ gestellt, but finished serene
- CU19 installed
- Server restarted
The individual Exchange 2013 server has started cleanly and appears to be functioning normally. If you are running an Exchange 2013 DAG, you must first put the DAG into maintenance mode (Performing maintenance on DAG members)
Nicht vergessen die Exchange Dienste nach dem ersten Neustart wieder auf Starttyp „Automatisch“ zu stellen, sonst schlägt die Installation von CU19 fehl:
Update 26.01.2018
The method described above is now also available as a note on TechNet:
Nevertheless, care should be taken to ensure that the Exchange servers are provided with the latest updates.