I have a project I'm working on and looking for some info. Right now I have a VPN network using Cisco Pix 501's for the vpn clients and a Cisco VPN Concentrator 3000 for the VPN Server.

Since the Pix is constantly connected to the vpn, I want to add a extra level of authentication. Meaning when the user on the other end goes to access anything on the VPN they are asked for a username password before the connection is established.

I've never done this sort of structure before. So I'm not even sure where to really being or even if my current hardware can do something like this, or if i need to through in some sort of radius/LDAP/Active Directory type server into the mix.