Sorry no Internet

Troubleshooting – Isolating the cause

This post is the second in my three part series on troubleshooting. In last weeks post I focused on the importance of building trust with your client by asking the right questions to solicit the valuable details you need to appropriately diagnose an IT problem. This week I will talk about the importance of isolating a specific cause.

Step 2 – Isolate a specific cause

A lot of time is wasted in IT troubleshooting due to anxiety over coming up with a fast solution. People want to impress their boss, their customer, or their colleagues so they quickly form an opinion as to what the client needs and try to implement a fix without first taking the time to isolate the problem.

Slow is smooth, smooth is fast.


Think through the symptoms, think about what system or systems they all have in common. Use that information along with other knowledge you have gained through training, education, and experience to narrow down the possible causes. Slow is smooth, smooth is fast. You isolate an issue by gathering data, coming up with a hypothesis, and then attempting to prove that hypothesis to be wrong.

Lets take what we have learned for a spin

Scenario – I don’t have the internet!!!! OMG my life is over please help me!

Sorry no Internet

After asking our customer all the necessary questions that we discussed in The Art of Asking Questions we find out that the user discovered this issue when he couldn’t reach his favorite news site. Further investigation shows that he cannot reach any site on the internet or the intranet, running ipconfig reveals that he is receiving a valid ip address, and he can ping the gateway by ip address.

Isolate a specific cause

Again ask more questions do not assume that this is a large scale DNS issue, it could be, it could also be a virus that corrupted his hosts file, or maybe he messed with the DNS settings on the network adapter trying to bypass the company servers. Remember you don’t know yet, you are still agnostic.

Is anyone else in the office having this issue?

What does this question do for us? It can potentially eliminate a lot of problems that would be very expensive. If this is an office of 10 people all of whom have workstations that are connecting to the internet, network shares, and intranet sites; then you do not have a wide scale DNS problem. The ISP is not at fault since others are not effected so you can eliminate the router, the ISP, the DNS and DHCP servers, as possible causes. Just by asking a question.

From what we have gathered after asking all of our questions we know that the problem is with DNS, but that it is only effecting the local computer. What components are in play? The hosts file, a proxy redirect, an incorrect DNS setting on the network adapter, maybe a virus. Start with any component you like and work your way back verify that each is set correctly eliminating each as a cause until you run into one that cannot be excluded.


I used DNS as an example here, but the same methodology can and should be used when dealing with hardware problems, software installations, network connections, authentication etc. Ask your clients questions. If you build a strong relationship with them then the answers you get will contain reliable information that you can use to help you isolate the problem. If you ask the right questions you can eliminate many possibilities without even having to do any real technical work.

The lesson here is patience and persistence. Don’t be the person who insists that they know what the problem is until you have eliminated every other possibility (or the most common ones at the very least). Skipping the isolation phase is very tempting, especially for people who are just starting out and are trying to prove themselves, don’t do it! Step back, take a breath, gather your thoughts and verify, verify, verify. Analyze all the symptoms and prove every other possibility to be false before you spend time and money fixing something that isn’t broken.

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