Troubleshooting Linux Firewalls

  1. Recognize, Define, and Isolate the Problem

    • What is the problem?

    • Isolate the problem.

    • What is the scope of the problem?

    • Can you duplicate the problem? This is a critical step; if you cannot cause the problem to occur again, you will not be able to test your solution.

    • Prioritize the problem(s). Is this something you have to fix right now?

    • If it's a particularly difficult, boring, or unpleasant problem to solve, try the "ten minute plan." Just tell yourself you'll work on it for ten minutes. For most people, after they start working on a task, even an unpleasant one, they will commit to it. It's getting started that is the chore, not continuing to work on it.

  2. Gather All Pertinent Facts About the Situation

    • The Golden Question: What Changed?

    • What's common to this problem?

    • Does it happen from everywhere on the network?

    • Do all OSs seems to be affected by this problem?

  3. Define What the "End State" Should Be

    • How should the system or systems behave normally? In other words, do you know what the correct behavior is? Make sure you clearly define that; otherwise, you will not be able to test the system to determine if it is functioning properly.

  4. Develop Possible Solutions and Create an Action Plan

    • Develop possible solutions.

    • Develop a plan for each solution.

  5. Analyze and Compare Possible Solutions

    • Start with the simplest problem first.

    • Start with the simplest solution first.

  6. Select and Implement the Solution

    • Track changes and give yourself the ability to roll back.

  7. Critically Analyze the Solution for Effectiveness

  8. Repeat Process Until You Resolve the Problem

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