The primary tools for troubleshooting VPNs are the show, ping, traceroute, and debug commands. For these commands to be used correctly (and safely), a number of guidelines need to be followed.
The show command can be used to view a wide variety of information and statistics related to VPNs.
The ping and traceroute commands can be used to verify basic IP connectivity and route across the network. The traceroute command can also be used in an MPLS backbone to display the label stack. Maximum Transmission Unit (MTU) issues that may result in a VPN can also be identified using extended ping to sweep a range of packet sizes. If pings using smaller packet sizes succeed but larger packet sizes fail, this can indicate an issue with ...