Does the pix 515e 6.2 support l2tp certificate authentication through itself to a 2k3 server using the Windows XP native vpn client? I can get it to work with a Windows 2000 native client. For some reason XP does not work, although it works on the intranet, not going through the firewall. Something in the PIX is stopping the XP client. Like I said, I seem to have all the right ports open as I can get it to work with a Windows 2000 machine. I read somewhere that XP and l2tp with NAT does not work without modifying the registry? I dont want to authenticate TO the pix, I just want to go through it.