Diagnose and fix network problems yourself

“So, follow along with us now as we review some of the network
diagnostic tools in Linux and see how to use them to get answers to
the question “what’s wrong with my network?”

“The most important thing, when you’re trouble-shooting
something, is to have some idea how it’s supposed to work in the
first place. Does your machine have a static IP address, and if so,
what should it be? Does it use DHCP, and if so, where is the DHCP
server, and what range of IP addresses is it expected to allocate?
Do you have a broadband modem directly connected to your machine,
or do you have a separate broadband router to which you connect via
ethernet or wireless?

“Our methodology in this tutorial is to take a “bottom up”
approach. We start by checking the really low-level stuff first,
then gradually work our way up to higher levels. The sequence of
tests we’ll perform is summarised (approximately) in Figure 1,
below. This is a good, systematic approach for network connections
that have never worked. On the other hand, if it was working fine
yesterday, it’s generally faster to start at the top and work your
way down.”

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