The VPN 3000 Concentrator series is the most popular and highly deployed VPN appliance in today's network primarily because of its Remote Access Client Virtual Private Network (VPN) connections. You can also build up LAN-to-LAN VPN tunnel with a wide variety of devices with VPN 3000 Series Concentrators. This chapter examines the troubleshooting aspect of the VPN 3000 Series Concentrator in greater detail. The Case Studies section contains the configuration and troubleshooting of SSL VPN in greater details based on the new version, 4.7. For a higher-level explanation of IPsec in general, refer to Chapter 6, "Troubleshooting IPsec VPNs on IOS Routers".