Event ID 720

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VPN Error 720 - the connection attempt failed because your computer and the remote computer could not agree on PPP control protocol - Case 2

Uninstall/Reinstall the TCP/IP Protocol

Symptoms: 1. When attempting to establish a VPN, you may receive the following error message during the "Registering your computer on the network":

Error 720 - the connection attempt failed because your computer and the remote computer could not agree on PPP control protocol.

2. If you view the devices in Device Manager, you may notice a yellow exclamation mark (!) over the icon for the WAN Miniport IP (#2) device.

Resolution: To resolve this issue, uninstall the TCP/IP protocol, remove the second WAN Miniport IP device, and then reinstall the TCP/IP protocol. To do so, follow these steps:

Uninstall the TCP/IP protocol. To do so:

a.	In Control Panel, double-click Network and Dial-up Connections, right-click Local Area Connection, and then click Properties.
b.	Under Components checked are used by this connection, click Internet Protocol (TCP/IP), and then click Uninstall.
c.	Follow the on-screen instructions to uninstall TCP/IP.
d.	Restart the computer when prompted, but click No if you are prompted to allow Windows to enable a protocol.

Right-click My Computer, and then click Properties.

Click the Hardware tab, and then click Device Manager.

On the View menu, click Show hidden devices.

Under Network adapters, there should be no WAN Miniport IP devices. If a WAN Miniport IP device is listed, continue to the following step. If no WAN Miniport IP device is listed, go directly to step 16.

Click Start, click Run, type regedit in the Open box, and then click OK.

WARNING: If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.

Locate the following registry subkey:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E972-E325-11CE-BFC1-08002BE10318}

On the Registry menu, click Export Registry File, type backup-key in the File name box, and then click Save.

Note You can restore the changes that you make to this registry key. To do so, double-click the backup-key.reg file that you saved.

Click each of the registry subkeys under this key, and then view the Data column of the DriverDesc value to determine which of the subkeys corresponds to WAN Miniport (IP). For example, the 0005 subkey.

10.

Right-click the subkey whose DriverDesc value data is WAN Miniport (IP) (for example, right-click 0005), and then click Delete. Click Yes to confirm that you want to delete the key.

11.

Quit Registry Editor.

12.

Right-click My Computer, and then click Properties.

13.

Click the Hardware tab, and then click Device Manager.

14.

On the View menu, click Show hidden devices.

15.

Under Network adapters, right-click WAN Miniport (IP) and then click Uninstall. Click OK to confirm that you want to remove this device.

16.

Reinstall the TCP/IP protocol. To do so:

a.	In Control Panel, double-click Network and Dial-up Connections, right-click Local Area Connection, and then click Properties.
b.	Click Install.
c.	In the Select Network Component Type dialog box, click Protocol, and then click Add.
d.	Under Network Protocol, click Internet Protocol (TCP/IP), and then click OK.
e.	When the protocol is installed, click Close.

17.

Reset the modem by turning the power off and then on, or for an internal modem, restart the computer.

18.

Test your Internet connectivity.

If it is XP, you may use netsh to reset TCP/IP following these links,

How to reset tcpip in xp

How to reset TCP/IP in Windows XP. When viewing the list of components for a network interface in Windows XP, you may notice that the Uninstall button is ...
www.howtonetworking.com/Windows/resettcpip1.htm

How to reset TCP/IP in Windows XP

In Windows XP the Uninstall button is disabled when Internet Protocol (TCP/IP) is selected. To reset the TCP/IP in XP, you should use netsh utility, ...
www.howtonetworking.com/Troubleshooting/winsock2corruption8.htm

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