In some cases when using a VPN over a network connection with a Windows XP computer, the VPN Session will disconnect after a period of inactivity (typically 10 to 20 minutes). This problem is caused by the Windows Service Pack 2 Firewall settings.
To fix the problem, the Windows Firewall needs to have the Cisco VPN Client program specified as an Exception:
Click on the START tab, and select:
Control Panel -> Windows Firewall
The following screen will be displayed. Click On (recommended) if not already on.
Click the Exceptions Tab which will bring up the following screen:
Click Add Programs which will bring up the following screen:
Click Browse and set the directory to look in to C:\Program Files\Cisco Systems\VPN Client.
Highlight the cvpnd program (single click), and then click Open .
Click OK as necessary.
At this stage the cvpnd program should have an entry as above. Click on OK to finish.
These settings for the Windows Firewall will stop the VPN session being terminated after 10 to 20 minutes of inactivity.