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Error 721 VPN connection

Hey I got one,

I am trying to set up a VPN connection and am recieving this 721 error. Here is the situation. I have (2) PC's, seperate accounts and both users have dial in access. Both are connected through a DLINK DSL-G604T and have internet access. Both machines are running XP with the latest service packs and updates. One PC can VPN and the other cannot. Thinking that it was a problem with having multiple VPN clients through the router, I disconnected the first and tried to VPN on the second. I still receive error 721. I then tried the other(working) username which connected on the first machine and the problem was the same. Both accounts have known dial in access and work. Having even tried disabling Windows Firewall with no solution.  Both VPN connection settings are identical. It is just that on this one PC I cannot VPN in, no matter which account I use I still receive Error 721 not responding. Looking into the event viewer,  on the responding server (Win2K3) a message displays something about the remote firewall. I do not think that it is because I can VPN on one PC and not the other.

" A connection between the VPN server and the VPN Client XXX.XXX.XXX.XXX 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 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 users network are also configured to receive GRE packets. If the problem persists, have the user contact the ISP to determine wether the ISP might be blocking GRE packets"

I do not think that the above information is the solution.  

So in summation, I have (2) PC's attached to a DLS Modem/firewall/router. PC1 can VPN in with no problems, PC2 cannot. VPN connection settings are the same.

Any thoughts????
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edelit
Asked:
edelit
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1 Solution
 
Rob WilliamsCommented:
To confirm, both PC's are behind the same D-LINK DSL-G604T, and no other routers or devices exist between the D-Link and the PC's?
You are correct that very few router s will support more than one simultaneous PPTP connection. So you will only be able to connect one PC at a time.
A 721 error, as you have noted, is usually due to blocked GRE packets. However your server and routers must be configured correctly if 1 PC can connect. Only suggestion I have is completely uninstall the VPN client on the problematic PC and re-install. I have had this resolve the problem more than once. It is possible the packets are not being formed correctly if the installation was somehow corrupted.
Also on the problem PC make sure the Windows firewall or any other software firewall is disabled, at least for testing purposes.
If any doubts about configuring the VPN client, following site is excellent:
http://www.onecomputerguy.com/networking/xp_vpn.htm
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edelitAuthor Commented:
Yes that is correct both PC's are behind the same DLink DSL-G604T np other routers, switches, hubs or firewalls in place. Other then Windows firewall active. We are using the Microsoft VPN Client to connect so I do not htink that you can uninstall the service such as a normal Windows component. If you know of a way to unregister the service and reregister that might do it. In the meanwhile I'll keep fishing.

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Rob WilliamsCommented:
The Windows firewall can definitely block GRE packets, however where it is outgoing that should not be an issue. But, there is initial handshaking the firewall may consider as incoming traffic. I am not suggesting removing the firewall but rather disable it temporarily for testing. It is configurable to allow that traffic, so if disabling it resolves we can look at creating the proper exceptions. To disable go to  control panel | Windows firewall | off
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edelitAuthor Commented:
I have tried with the firewall disabled and still no avail.... is there a way to register the VPN client such as the regsvr32 command?
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Rob WilliamsCommented:
>>"is there a way to register the VPN client such as the regsvr32 "
None that I am aware of.
Have you tried re-installing the VPN client? It is also possible it could be a network card driver problem. Perhaps check for newer drivers if available, or re-install existing.
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edelitAuthor Commented:
I was thinking on the NIC, I think that I may try to reload the OS since the VPN is Microsofts client. Thanks for the help.
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Rob WilliamsCommented:
Thanks edelit . I hope the re-install works out for you. Odd problem.
--Rob
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