We have a windows 2003 domain and are planning to install a Cisco Pix 515 firewall. I've already configured a few Pix firewalls for Pix to Pix tunnels, and basic client VPN sessions using pptp and a username and password contained in the pix's configuration. What we would like to do with the Cisco Pix 515 at this particulat site is allow users to connect to the network via a VPN connection, using their Active Directory username and password. How can we achieve this? Would we need to purchase any additional software or hardware.