I installed a Windows 2003 PPTP/L2TP VPN server. After the server installation I started testing the communication by creating a VPN connection. The first error I got while connecting was “Disconnected. Error 721: The remote computer did not respond“. The Windows XP client is running as a VMWare virtual machine and the VPN server is published behind a Cisco PIX 501 firewall.
I checked the VPN server and there I saw the error message below. I verified the NAT configuration and a static NAT rule was configured based on a private and public ip address translation. ACL was there for ‘any’ tcp communication and I added second ACL for IP Protocol 47 (GRE).
I logged on my Windows Vista Enterprise client and recreated the same VPN connection. The Vista client was connected to my ADSL modem with a wireless connection and it had direct connection to the VPN server. The Windows XP virtual machine was sitting behind the Cisco PIX. I figured out something was missing on my firewall configuration.
How to allow PPTP protocol on a Cisco PIX firewall?
pixfirewall# conf t pixfirewall(config)#fixup protocol pptp 1723 pixfirewall# wr mem
Adding the “fixup protocol pptp 1723” to my configuration let the Cisco PIX firewall know how successfully setup a PPTP connection.