Summary

You use the same set of troubleshooting tools to diagnose and gather information about site-to-site VPN connections as remote access VPN connections. The exception is the Unreachability Reason, which is used to determine why a demand-dial interface failed to connect. The most common problems with site-to-site VPN connections are the inability to establish a successful connection, the inability to reach locations beyond each VPN router, the inability to reach the virtual interfaces of each VPN router, and on-demand connections not being made automatically.