We have a single publisher/subscriber running 7.1.3 as well as a single Publisher Unity Connection server running 7.0.2 and Cisco Emergency Responder 7.1.3. There are several questions that I have pertaining to our production environment. We have roughly 300 phones. Can we do the upgrade to the CUCM servers while the CUCN and CER servers stay at said state versions? What effects of the CUCN (7.0.2) and CER(7.1.3) running with CUCM servers running 8.6.2a?
2. Do we have to upgrade all four servers at once?
3. Can one PRI run two cluster environments running on two different versions?
Just to add for question 3 as Vipul said (+5) with H323 it's as simple as pointing different dial-peers to different CUCM servers, so you may need to break your DID ranges, or you can simply route all calls to one cluster and then transfer appropriate calls to another via Intercluster trunk, so this would not require H323 and would work with any protocol.
For question 1-2 see the compatibility guide for links to appriopriate UCON and CER compatibility information:
Are you getting this error “Installer User Interface Mode Not Supported. The installer cannot run in this UI mode. To specify the interface mode, use the -i command-line option, followed by the UI mode identifier. The value UI mode identifiers...
The below trick might come handy when you have to add a new node to a cluster but you don't have or is unsure of the security password for the publisher. This procedure has been around for ages.
1) Login into the CLI of the Publisher.