Cisco NAC technical information

Question

Hello everyone,
So I've been looking through the Cisco website trying to get information about Cisco NAC (at the request of my boss, the IT team leader). Unfortunately, all the information about NAC on this website is geared towards supervisors and purchasing authorities; I haven't been able to find any sort of real technical data, just a bunch of sales mumbo-jumbo. I know a lot about what it can do, but nothing about how it does it.
I would like to know how this system would interact with my network. I'm newly in charge of an almost pure Cisco network consisting of a couple dozen Catalyst 2950 switches and 3 Catalyst 3750 stacks in various positions throughout the network.
Our network uses a star-topology, meaning all the switches tend to radiate from the central Layer 3 switches (the 3750s), meaning we don't, at the moment, have any sort of redundancy like in the Cisco-recommended Core-Distribution-Access topology. We want to get to that point sometime in the future.
Anyways, I'd like to know how I can integrate Cisco NAC into my existing network. How would it connect and where? How does it regulate access? Do all computers require some kind of client to be installed? How does it regulate VLANs (of which we have about 50)?
Like I said, we want to basically overhaul our network sometime in the future, but I'm not really counting on it happening soon, so I'd like to know how NAC would be implemented in our current network so that we may be able to enjoy some of those benefits right away.

Answer 1

My explanations / answers are not authoritative but should provide some general idea about things you could accomplish with this product.
1.) Since you are basically all Cisco you will probably use an out-of-band solution. This allows the NAC to "manage" your switch ports. As the sales literature suggests it's about mapping users/ips/macs to roles and allowing access based on the role. Example would be new device plugs in to a perm switch. You require that all machines have AV, New Defs, and Latest Updates. The client would use the agent to validate it has met these requirements. If not the agent may recommend (at your pref) how to meet the given requirement - I personally like the idea of providing links to pages where they can find information on fixing the issue. Once the 3 requirements are met you allow the system access to your network on a given vlan in a specific role.
2.) Again, because your switches are all Cisco you have many options. Primarily in-band vs out-of-band. I have very little doubt you would choose out-of-band with the description of your topology given above.
3.) Connection would be 2 ports on your 3750 stack.
4.) It regulates traffic by performing requirements checks and by mapping machines to a given role. That role is aloowed to do certain activities on your network. I kinda of think of role management like a firewall of sorts. Once you are authenticated to a given role you are allowed to do things like surf the internet or ftp to an internal server. Each role could be given different access ability.
5.) Technically no machines "require" a client to be installed. You can use a combination of web login with scanning and / or cisco agent installations. For linux machines no agent is currently available to my knowledge. For macs and pcs the agent (once installed) seems to make access simplier.
6.) Vlan regulation depends on the type of install you choose. For example you may map vlans.
Hope that helps.
Greg W.