Using OPNET you should have manufacturer specs for most of the CISCO hardware built-in with the CISCO and AD modules.
My recommendation for a school AD environment, would be:
2 different kinds of AD forests. Forest #1 would be a real PRODUCTION AD Forest. Forest #2 would be a virtualized AD Forest running on VMWare ESX software. The virtual forest would allow students to play with the schema and blow it up without affecting production. They could also model AD's behavior and if they screwed up a setting, it is a short re-install from an image rather than a torturous rebuild of physical boxes.
Peer-Domain Empty Root Forest Design with 3 domains:
PRODUCTION
Root of Forest (myschooldesign.local)
Floor A Domain (FloorA.local)
Floor B Design (FloorB.local)
This would offer maximum security to the root of the AD Forest and allow more granular security control over domains, ie you could assign domain admins that would only have authority to screw up their domain and not someone else's.
Design to include the following:
Forest in Windows 2003 Functional Mode.
All domains in Windows 2003 Functional Mode.
All domain controllers to be global catalogs.
Server Specs:
Quad processor with 16 gig of memory.
Network Infrastructure
GIG E Fiber
Cisco Switches of your choice based on your port requirements.
F5 switches if you really want to go all out.
Cisco Load-Balancers.
Don't forget the DMZ and Exchange needs. You will need application servers for all the SQL, Exchange, Proxy and Bastion Host requirements.
Also account for your DHCP needs.
Virutal AD forest
For the virtual AD forest, you simply need VMWare and recreate your forest on it. Then students could blow it up to their heart's content and not affect the real production environment.
Best of luck with your studies.
One of the better books for AD is Notes From The Field. You can pick that up on Amazon for a nominal cost.
