Analyze the connection process and significance of the errors with we can find when trying to connect via modem or VPN:
1. Connecting: when receiving a 678 or 800 error while trying to connect to VPN server, a firewall that is blocking the connection. Add exceptions to your firewall or antivirus.
2. Verifying username and password: if connection is good, the VPN server will check permissions. In this process you may receive the error 691 if put their evil user credentials. If instead, the error you receive is 649, is because your account is passed without the markings.
3. Check the connection protocol GRE later to verify the username and password. If the protocol is IP 47 locked, you may receive the error 721. Check your firewall
4. Checking the configuration TCP/IP: After checking the name username and password, you may receive the error 733 while searching your computer on the network. If so, you must have a problem in the TCP / IP configuration of your computer. Reinstall the TCP / IP stack
5. A very common error in the VPN connection from home is the error 619 . This error is given because the router is configured to do NAT in home network, allowing multiple computers to connect to the Internet simultaneously. If this is your case, use the Cisco VPN client for connect.