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I have a user that is having trouble VPN to the office. What are you top troubleshooting things to try to find out where the problem is.

The error the user is getting is 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 this is that there is at least one internet device between your computer and the VPN server is not configured to allow GRE protocol packets Verify that protocol 47 GRE is allowed on all personal firewall devices or routers. if the problem persists, contact your administrator.

This sounds like a problem with the users router which is blocking VPN traffic. Does anyone have any tips for fixing this error.

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1 Answer 1

Yes, this definitely sounds like an issue with their router. GRE or Generic Route Encapsulation protocol is used in point to point tunneling and uses TCP port 1723 and IP protocol 47. In order to fix it the user needs to enable enable PPTP/GRE pass through. I do know that alot of lower end Linksys routers do not allow you to enable this, I'm sure there are other brands that have this problem too. If it helps I'll include some additional reading on PPTP/GRE: http://support.microsoft.com/kb/241251. As long as TCP port 1723 is open or forwarded and IP protocol 47 is allowed it should work.

EDIT: You might want to try having the user turn off UPnP or assigning their PC a static address. I was reading this may cause issues with GRE, worth a shot.

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Certain SPI implementations will can also cause problems too. –  user48838 Nov 12 '10 at 10:32

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