Just purchased numerous Vienna Libraries, Vienna Ensemble Pro 5, and Vienna MIR RoomPak Bundle.  I am using Sonar X3 Producer with Windows 7 Ultimate 64 bit, running 12mb RAM.  Since I'm working with large orchestras, I need far more than 16 channels.  Would like detailed, step by step instructions on how to do this.  I'm a composer, not a tech person, so non-tech language please.  Thanks!

Ability to run more than 16 midi channels from a single midi track - is that what you need?
That is what VST3 implies using multiple midi ports on a single instance VST instrument.
 
Otherwise it's just selecting midi target port and midi channel on each midi track - as I understand it.
Writing for orchestra you have one midi track for each instrument even, or?

The other way to get multiple midi ports to multiple external instances is to use a software midi setup .. something like loopMIDI ... then from inside sonar it is not much different than connecting a physical midi cord to a hardware synth. 

I need to use more than 16 channels for my Vienna Libraries.  I get that Sonar has unlimited tracks, but I will need a separate track for each instrument and since each instrument/track needs to be assigned it's own channel, I'll run out of channels.  In the past, I circumvented this problem using multiple external sound modules with each one being capable of 16 channels.  Don't know how to accomplish this with Sonar X3 and the Vienna Libraries.  Sorry, I'm new to this so it's a bit confusing.  Does VST3 allow me to choose different ports?

You will need to upgrade to SONAR Platinum for this functionality. We added support for VST3 event buses in the latest version which allows outputting to more than 16 channels for a single Vienna instance.
You can read more about it in the documentation.
Also some more notes here in the section VST3 MIDI input buses.

Vienna Ensemble is known for ability to run externally - even on other computer in a network.
How do you plan to run it - as local VST Instrument, or outside Sonar?
 
If external, is VEP providing virtual midi ports that can be assigned as if they were physical midi ports?
Or do you run multiple instances of VEP - then each will get a midi port, I assume?
 
EDIT Alright, Noel had full info....

As a local VST instrument.  It appears that, according to Noel's post above from Cakewalk, that I will need to upgrade to Sonar Platinum in order to accomplish this.  Thank you for helping.
 
Noel, if I understand you correctly, once I upgrade to Platinum, I can use the Vienna Libraries on numerous Ports?  How many ports are available?

Any single midi track can be routed to any of the exposed midi inputs on VEP.
You get a submenu of inputs to connect to on that instrument.

Ok.  Thanks!

JLawson-Composer
As a local VST instrument.  It appears that, according to Noel's post above from Cakewalk, that I will need to upgrade to Sonar Platinum in order to accomplish this.  Thank you for helping.
 
Noel, if I understand you correctly, once I upgrade to Platinum, I can use the Vienna Libraries on numerous Ports?  How many ports are available?

Hello there is a max of 256 MIDI event buses per track in SONAR. That gives you 256x16 channels which should be plenty :) You basically configure the number of ports you want in Vienna and SONAR will automatically discover them when you add a vienna instance. In the MIDI out ports field you will now see virtual ports listed for these.
Vienna support should be able to assist you should you need more info.