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The Basics

To get the best out of this book's advanced topics and to help yourself with your career in IT, you should have a good understanding of some basic concepts and technologies. Without this understanding you'll struggle with the more advanced topics and your foundational knowledge will be weak.

Please trust me when I say that understanding the fundamentals is going to be very important for your career. If you build your career on shallow, weak foundations then you're going to struggle to debug problems in the future.

A good example of this is networking.

A Scenario

You've come into work one day and you're told employees cannot access your company portal website: portal.mycompany.corp. You're told the error is, "HTTP 502 Bad Gateway". You get to work debugging the problem.

After visiting the website you see the same HTTP 502 error.

A few things will come to the mind of someone who has not studied and come to understand fundamental networking concepts:

  • What is HTTP?
  • What does the number 502 have to do with HTTP?
  • What is being referred to by "Bad Gateway"?

If your fundamental networking knowledge is sound you'll know that:

  • HTTP is Hypertext Transfer Protocol and operates on ports TCP/80 (and TCP/443 over TLS, also known as HTTPS)
  • The 502 is an HTTP 502 response code; looking up the code you'll see it means "Bad Gateway" which in turn means, "... 502 Bad Gateway server error response code indicates that the server, while acting as a gateway or proxy, received an invalid response from the upstream server"

So what steps does well informed administrator take?

  1. Resolve the DNS of portal.mycompany.corp to understand what possible HTTP servers are serving the HTTP 500 response
  2. Investigate what back end or upstream address/IPs and port(s) those HTTP servers forward or proxy the traffic to
  3. Determine if those upstream servers are online and serving the correct traffic on the correct port
  4. From there, debug why the application on the upstream systems is not serving traffic correctly

And so on.

The moral of this story is this: knowing what an HTTP 502 Bad Gateway error is, because you have fundamental networking knowledge, means you can quickly diagnose technical problems and solve them. The opposite of this is spending a lot of time looking embarrassed whilst you struggle to understand the problem and try to resolve the problem by turning it off and on again (this is actual advice I've seen people apply.)


Let's start this topic of by looking at the road map you're going to be following to progress into your career in IT.