In Chapter 11, “Troubleshooting Remote Access VPN Connections,” we went through the extensive and involved procedures for troubleshooting remote access virtual private networks (VPNs). The process for troubleshooting site-to-site VPNs is similar in many ways and uses the same procedures. We will go through the process in detail again for many areas so that you have a complete and comprehensive troubleshooting methodology to use. Where it doesn’t make sense to repeat information, we will refer to Chapter 11. In this chapter, we list the set of troubleshooting tools provided with Microsoft Windows that you can use to gather information about connections, and then describe what to look for to correct the most common problems with site-to-site VPN connections. Remember from the previous chapter, the two things to keep in mind when trying to troubleshoot VPNs:
“Divide and conquer.” To isolate the problem, rule out components individually, and eliminate them from the troubleshooting equation.
“This troubleshooting stuff really works!” Don’t get discouraged. Keep plugging away if you are having problems, and make sure you work with all the tools available.