Imagine some network engineer or CSR starts to troubleshoot some problem. They ping from the user’s host, ping from a nearby router, and after a few commands, convince themselves that the host can indeed send and receive IP packets. The problem might not be solved yet, but the problem does not appear to be a problem with packet delivery between the user’s device and the rest of the network.
Now imagine the next problem comes along, and for that device, pings fail. It appears that some problem does exist in the IP network. Where is the problem? Where should the engineer look more closely? While