Problem establishing VPN connection with remote server

2,015 pts.
Tags:
error 721
VPN issue
Windows XP SP3
One machine is having a problem establishing a VPN connection with a remote server. It hangs on verifying the username and password. Another machine on the same network, using the credentials of the user who has the problem connects straight away. This has led me to believe that the problem is entirely with the one machine. I've updated the NIC driver with no success. I have created a new VPN connection but get the same results. I have even shut down the firewall on the local machine without gaining anything. This connection was working in the past. I have not been able to put a finger on the problem and I am looking at doing a complete re-install of the OS right now. The error returned is "721: The remote computer did not respond." I did check ADUC and the user is allowed to connect remotely. Does anyone have any suggestions?

Software/Hardware used:
Windows XP SP3, Microsoft VPN Client
ASKED: February 25, 2011  9:40 PM
UPDATED: June 27, 2013  4:57 PM

Answer Wiki

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I had similar troubles when I installed a program to manage voip comunication inside the company. This software had installed another network interface and that was the problem. Once uninstalled I have been able to connect to the vpn network again.

Another software who creates network interfaces are virtual machines managers like VirtualBox or VMWare.

Search for a recent change in any of the interfaces of the machine with troubles.

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  • Sixball
    Since you mentionjed WinXP, that indicates a PPTP VPN connection - What does your VPN connection Log say? Any insight into the VPN process would be helpful. Also, Redoing the OS may or may not be necessary. Updating the NIC drivers seemd like an unneeded step as well. Ensure the Proper services are either started, or set to automatic on the affected machine...
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  • saturno
    Using WIndows XP VPN *does not mean* PPTP VPN, it can be also, among others an L2TP VPN. This leads em to one of the first things to consider. Using some types of routers (without support to NAT-T), and in case it is an L2TP VPN, you might need to tweek Windows XP registry to make it able to connect remotely. It would take a while to explain here, so a rather point you to one article in the web that explain this "problem" and how to bypass it. Try this, and give us some feedback and more info in case it doesn't resolve your issue. HTH
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  • Stevesz
    Sixball, I was not aware that the VPN connector kept a log, other than, perhaps entries into the event logs. I searched for such a log for VPN, and could not find it, and the event logs both on the local machine and the remote server do not show any events related to a VPN connection problem or a logging problem.
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  • Stevesz
    Saturno, I do not believe that NAT transversal is the problem in this instance. I've since tried the VPN connection on three more machines here at the shop, and every one of them connects just fine (and one of those machines is in pretty poor shape and will be re-imaged shortly). As I mentioned in my original posting, this connection had worked fine for some time, and then just quit. The other network interfaces are those that have been on the machine since it was new, and never caused a problem ad Mariodlg suggested might be a cause. I have also discovered that VNC is no longer working either. I am thinking that something may have happened that tore up the networking components of Windows somewhat, and this is what is causing the problem.
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  • Subhendu Sen
    This vpn error 721 may occur, after making an unsuccessful attempt to establish a dial-up connection after upgrading ur computer to Microsoft Windows XP from earlier versions. This error may vary time to time from remote PPP peer is not responding to the remote computer.... U need to configure network firewall to permit the GRE (Generic Routing Encapsulation) protocol 47 (if u use the same). Also, need to make sure that firewall permits the TCP traffic on port 1723. One more try for Installing the latest Windows XP compatible driver for the modem can also fix the problem.
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  • saturno
    Well, Try to connect directly through GRE port of the other side of the tunnel you are trying to make the VPN. (telnet INSERT_IP_OF_THE_HOST 1723), if this is not the problem, you should have an empty DOS screen with cursor blinking. As already said, it might be a firewall issue. When debugginf this kind of problems, you should disable temporarily any firewall between those two test machines. Finnaly, considering that XP *is clean*, try to rebuild the TCP/IP stack issuing this command:
    netsh int ip reset <filename>
    where filename is any filename. This is a log file created by the above command to keep track of what was done. Keep us posted
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  • Stevesz
    I am not sure that you guys are actually reading my problem here. The problem exists only on the one machine. other machines on the original network, and another network connect just fine. I have shut down the firewall on the affected machine with no improvement. VMC, which does not rely on GRE is also affected. E-mail and other web connectivity is not a problem. I suspect a problem with one or more of the Windows networking components on this machine.
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  • saturno
    Fine, What was the output of the command:
    netsh int ip reset <filename>
    If rebuilding the TCP/IP stack did not solve the problem, without asking you no more information about, I think you have two choices: - Put wireshark on both ends and debug the connection; - Reinstall the OS on that single machine.
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  • Stevesz
    Saturno, The netsh reset took care of the problem. I don't think you really want to know what the output was, but the VPN is once again working. 10 entries were added, 15 were deleted and the rest were reset. Sometimes, being a generalist just does not work out so well anymore.As soon as I read your post, I knew that is what I should have thought of near the beginning. It has been a while since I have had to use any of the netsh commands. The problem is resolved, and thanks!
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  • saturno
    Great! Thanks for the feed back!
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