Verifying IP Connectivity and Troubleshooting

At one point or another, every administrator must troubleshoot a user's complaint of not being able to reach some destination on the network. Lack of connectivity can be the result of network outages caused by WAN service failures, misconfiguration of routers and other devices in the network, access list controls (whether intentional or otherwise), and myriad other possibilities. Although there is no substitute for network test equipment, such as protocol analyzers, the router does provide several very useful tools for verifying IP connectivity and investigating potential problems. Let's examine a few of those tools.

As mentioned earlier, a router should have a specific route or some kind of default ...

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