I had IAS working on a 2003 server as a RADIUS server for authentication to a Cisco ASA for VPN connectivity.

1                     Create a RADIUS Client on the NPS

2                     Create a network Policy as follows;

1. Right click network policies and click new
2. Type a policy name accept the defaults and click next
3. Add a condition (I used a windows group with my users in it), click next
4. Make sure the access granted radio button is selected and hit next
5. Select the “Unencrypted authentication (PAP, SPAP)” and unselect the rest
6. Select NO on the annoying help box
7. Finally select next then next and finish to complete.

3                     Configure your Cisco device for RADIUS as you would have with 2k3.