The network problem has been officially resolved after you’ve implemented a change, observed
that the symptoms have disappeared, and can successfully execute the tests that were used to aid
in gathering information about the problem. In this example, the way to verify that the problem
is solved is for Host A to try to ftp to Host Z. If this test is successful, then the problem is resolved.
In the previous sections, we have emphasized that documentation is an integral part of troubleshooting.
When you keep track of the alterations that were made, the routers, switches, or hosts that
were changed, and when the changes occurred, you have valuable information for future reference.
There is always the possibility that something you changed might have affected something else and
you didn’t notice it. If this happens, you will have documentation to refer to, so you can undo the
changes. Or if a similar problem occurs in the future, you can refer to these documents to resolve the
new problem, based on what was done the last time. Later chapters in this book will give you more
information about documentation and establishing baseline information.