As I always understood it to be....that today if there is a requirement for UM and VM subscribers on the Same Unity system(s) (ie. Out of Box Exchange) then it can ONLY be done using the Unity UM licenses.....then for the users that ONLY need VM, we would turn off UM capabilities for them in particular.
Your understanding is correct - it's a licensing issue. If you want mixed VM and UM you can either do it as you describe or you can split the users across two Unity installations one with a VM only license and one with a UM only license. The former is obviously a bit easier.
On that note, have a customer who specifically setup VM on one Server and UM on another Unity Server. Main reason for this was to have enough vm ports available and # subscribers supported per hardware platform.
So as you say, they will need to do Unity Networking between the two Unity Servers both of which are homed to the same AD.
I have not done this before and need to replicate in lab first...where should I be looking for some serious docs on implentation guidelines.
What are some of the tips and caveats that I need to be aware of?
I'm in the process to do the same. There is a lot of information on the Networking in Cisco Unity guide, more specifically on section 2 for digital networking. Take a special look under the notable behavior. Keep in mind that live reply won't work between the servers and if there is a subscriber without a phone, it won't work also.(see call transfert behavior in the same section). As you know, if you have subscribers on both system, there will be 2 different pilot number. So, you have to be careful while programming a new phone.
as a side note, Unity 4.0(4) will address a couple of these issues - it'll support "handing off" calls to the appropriate Unity server such that callers can dial a single number to log into their mailboxes regardless of which server they are associated with in the dialing domain. Same thing for supervised tranfers - the call will be handed to the appropriate server first to do the transfer itself (this provides supervised transfer features like call screening and also deals with users that have no phones as you noted).
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.