Symptoms of this problem are that the VPN tunnel comes up, but the PC cannot pass traffic. Issuing the route print command on the VPN Client user's PC still shows the Dynamic Host Configuration Protocol (DHCP), static address, or both.
Microsoft routing problems occur when a Cisco VPN Client (such as a VPN 3000 Client, Cisco Secure VPN Client, or VPN 5000 Client) gets an IP address from the device terminating the tunnel that is on the same network as the local Network Interface Card (NIC). This device consists of the Cisco VPN 3000 Concentrator, router, PIX Firewall, or VPN 5000 Concentrator. This occurs if a user has a laptop on the corporate network with a DHCP or static IP address (10.50.1.x), brings the laptop home, dials into the Internet Service Provider (ISP), and connects using the VPN Client.
For troubleshooting steps, refer to VPN Clients with Microsoft Routing Problems.