What are Error code 800/721 when trying to connect to PPTP VPN?
There are many reasons why you get VPN error 721 and 800:
When a user attempts to access the Windows VPN server that is behind a Linksys WRT54G, he receives VPN Error 800 or 721.
Solution: Upgrading the firmware fixes the problem. Note: you may need to re-set the router.
When a user attempts to access the Windows VPN server that is behind a router, he receives VPN Error 800 or 721.
Solution: The port forwarding on the router pointed to other VPN servers. Modify the port forwarding to point to the current VPN server.
The user can establish the VPN from the desktop at home but not from the laptop.
Solution: Make sure no firewall software blocking the GRE protocol. Setup the firewall to enable the GRE connection will mostly fix the problem.
Some computers can establish VPN but one can't.
Solution: Same as above. Make sure other no secure software blocks your access, for example, if you use Norton secure software, you may need to add the remote client's IP so that the client can access.
The VPN server receives Event ID: 20169 - Description: Unable to contact a DHCP server. The Automatic Private IP Address 169.254.x.x will be assigned to dial-in clients. Clients may be unable to access resources on the network.
Solution: The server cannot contact your DHCP server to get a pool of addresses to allocate to clients and to itself for the internal interface. It is better to use Windows DHCP instead of router DHCP. If you are using Windows DHCP, you may setup static IP pool.
I have error in the DNS when VPN is connected, what can I do?
This can be done by Flush DNS commands in Mac. But if you need to flush the DNS cache in Mac OS X, be aware that the commands for this have changed through successive OSs, including Lion.
Flushing the cache is sometimes a good idea if you are unable to reach a site that you know is live but keeps returning an error (you can check whether a site is live for others.
Open Terminal (Applications > Utilities > Terminal.app) and use the appropriate command for your operating system:
In Leopard / Snow Leopard
In Lion and Mountain Lion
sudo killall -HUP mDNSResponder
With Lion, you’ll have to follow the command with your Admin password, which will be invisible when you type it.
My VPN doesn't work, can you help me please?
Mostly you can check below issues to troubleshoot your PPTP VPN connection problems:
Software Firewall – Check and make sure your firewall software is not blocking the VPN connection. The easiest way to test if it's conflicting with your VPN connection is to disable it and try the connection again. If this allows you to connect to the VPN you'll need to setup an exception in order to use the VPN while it's running. This will vary depending on your firewall software, but in general you will need to allow outgoing connections to port 1723 and the GRE protocol (47) also allowed. Alternatively you could set an exception for all traffic to the VPN server address.
Router – There is a possibility that your router doesn't support or isn't configured for PPTP VPN Passthrough. To test this, try connecting to the Internet without the router and see if it works. In other words plug your computer directly into your modem device bypassing the router.
A 2nd Computer - Do you have a 2nd Computer that you can try the account on, or a computer at another location? If so, try running it there. The VPN account will work on any PC, anywhere.
Error in Creation - This one is unusual but it does happen. For whatever reason sometimes the second time when you create a VPN connection it will work. So delete your first one, and try again.
Reboot - As always, a reboot on any device can't hurt. System resources and memory can run low causing all sorts of problems. Try to reboot your PC, Router, and Modem, then once the PC returns start VPN before opening any applications.
- Vista UAC - Customers have found that disabling UAC will sometimes allow OpenVPN and even our PPTP connections to work.
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