Hi Guillaume,
If the NAC and NES are running under the same instance of tomcat then using the same port for JMX should be fine - similar to how both the nac and nes listen/use port 8080. Using a separate tomcat instance for NAC and NES, if that's what you have, is something that I doubt has been tested/certified and so therefore I'd recommend against that and suggest taking actions to remedy that which should be as simple as uninstalling the current services and reinstalling RA selecting an all in one setup (default install) or by selecting both the execution server and management server components via a custom install (because this should still install everything under a single service). If you did decide to do this, assuming things are separately installed right now, then:
a. please backup both the server (VM, filesystem, etc.)
b. please backup the database
c. during the reinstall phase you should either:
1. select to skip the db install and then configure the db connection afterwards; or
2. point to a new db and then configure the db connection afterwards. You don't want to point the installer to a db that was being used in production. The only upside to this option over #1 is that you wouldn't have to make the needed changes to the database.properties file since it will have already determined the appropriate driver to use.
All of this is quite easy to write. I realize it's not so easy to do. If this is the kind of setup you have though I would recommend doing this before attempting an upgrade of RA on your system. If you do have this kind of setup (separate services for nac and nes) then one of my concerns is how the upgrade will behave. Any problems/questions with any of this then feel free to reach out to tech support.
In either case, thank you for sharing your solution with us. It is greatly appreciated.
Kind regards,
Gregg