Event ID 20209

Event ID 20209 - A connection between the VPN server and the VPN client has been established, but the VPN connection cannot be completed.

Symptom: When try to establish a VPN, the VPN client may receive error 721, 800 or 806. The RRAS Event Viewer may have Event ID 20209 - A connection between the VPN server and the VPN client has been established, but the VPN connection cannot be completed. The most common cause for this is that a firewall or router between the VPN server and the VPN client is
not configured to allow Generic Routing Encapsulation (GRE) packets (protocol 47). Verify that the firewalls and routers between your VPN server and the Internet allow GRE packets. Make sure the firewalls and routers on the user's network are also configured to allow GRE packets. If the problem
persists, have the user contact the Internet service provider (ISP) to determine whether the ISP might be blocking GRE packets.

Case 1: The client can establish the VPN if he removed the router and connect to the Server directly.

Case 2: The client can’t establish the VPN using wireless. However, if he try to use wired, he can make the VPN connection.

Case 3: The client can VPN to his office from all places except home. At home, he has satellite service.

Possible cause: Many wireless/mobile carriers block that sort of data unless you pay them extra or order a static IP.

Case 4: The VPN on Windows 2003 server worked for one year. It stops to work after installed SP1. If removing the SP1, the VPN works fine.

Case 5: The user can establish the VPN from the desktop at home but not from the laptop.

Troubleshooting: He loaded Microsoft OneCare software that blocks the GRE. Reconfigured the OneCare settings fixes the problem.

case Studies - VPN error 721 and 800

Case 1: When a user attempts to access the Windows VPN server that is behind a Linksys WRT54G, he receives VPN Error 800 or 721. ...
www.chicagotech.net/VPN/vpncase800.htm

cannot establish VPN with error 721 and 800

The client setup VPN behind a Cisco 678 DMT. Whenever he tries to establish the VPN, he receives Error 721 or 800. Troubleshooting: 1. ...
www.chicagotech.net/cisco/vpngre1.htm

error 721 and error 800

I keep getting errors:721, or 800 when attempting to connect with XP ... dns name for the VPN connection to see if it is a name resolution problem or not. ...
www.chicagotech.net/Q&A/vpn25.htm

ras error code

Error 806: a connection between your computer and the VPN server has been established but the VPN connection cannot be completed. The most common cause for ...
www.chicagotech.net/raserrors.htm

Event ID Troubleshooting

Event ID: 2011 - Not enough server storage is available to process this ... Event ID 5701 - The Netlogon service failed to update the domain trust list ...
www.chicagotech.net/wineventid.htm