Microsoft IAS
I’ve been playing around heaps with Microsoft IAS recently - both in the office and at clients, and I have to say that its pretty sweet in comparison to some of the other big ticket RADIUS (Remote Authentication Dial-in User Service) servers out there. Not to mention that its tightly integrated with Active Directory, making it compelling for anyone requiring authentication on their networking devices.
So far IAS hasn’t failed me, one gripe is that it doesn’t support the same breadth of EAP inner/outer protocols as Juniper’s Steel Belted Radius (SBR). But given you already paid for it when you bought Windows Server 2003 (pretty sure it comes with the standard edition) it does a solid job – especially with the Cisco wireless APs I’ve been working on. No special RADIUS attributes or funky IEFT formatting for your NAS identifiers – it all just works 
One feature I particularly like is that you can set up two IAS servers that are part of a corporate domain, and with no additional configuration you can authenticate your AD users via IAS from either machine; great for when you need some form of redundancy (beware though: make sure your AD controllers are also redundant). Local user authentication against computer user accounts is a pain though, ’cause you have to specify the machines domain name (LOCALMACHINENAME\useraccount) instead of just the user name.
If you are doing a big integration job within a MS environment and want make sure that your user accounts are uniform across all your networking equipment – there should be no need to configure local admin accounts on your networking equipment – just hook them up to IAS/RADIUS and bobs yer uncle!
There are some really good articles on Tech Republic that guide you through getting IAS to work – definitely worth checking out before diving straight into the deep end!
