Stories from my Past: Troubleshooting with a red herring

Stories from my Past: Troubleshooting with a red herring

I often get surprising problems thrown my way that resist standard troubleshooting techniques. I had a customer once who said that after he bought a new laptop it had problems connecting to WiFi or wireless networks. He said it wouldn’t connect to his home network or the hotel. So when something doesn’t connect in multiple locations, its generally the device at fault not those separate and unique systems.

So I started off with the basics and we went through checking that the WiFi switch was turned his laptop, and that it was showing it was trying to connect in Network panel. I had him do a ipconfig /all at the command line and asked him for the IPv4 number. When he said it was 169 I realized instantly what the problem was. It is elementary for IT people when we see that number to realize that it means the DHCP server isn’t giving out an address for this computer to pickup. This happens for several reasons, but the most common is that the device needs to be rebooted. I asked him to reboot his home network and Viola it worked.

The reason I am sharing this with you is that just because it appears to the something, in this case the computer at fault, it doesn’t mean that is the truth. While you troubleshoot or diagnose a problem you have to avoid prematurely jumping to a conclusion even if some of the evidence appears to fit the profile. Often people realize what the problem is with their computer, but their belief doesn’t make it true. You have to carefully keep an open mind until all the evidence is in.

In this example, if the device had shown it was getting a proper DHCP address then it would have likely been something with the computer. Perhaps a firewall or Windows update disabled something important. It is even possible that his network may have changed without him knowing. Since he had a home network managed by his Internet provider sometimes ISP’s have changed the DHCP address and the router needed to be rebooted to get the new information. I told him that it would probably be best to reboot the router every month to avoid these kinds of issues. Calling his ISP about this issue would have not yielded results because ISP’s don’t have good records or would likely be able to explain why he ran out of DHCP address. I think his settings were changed by the ISP and that’s why he ran of out DHCP address. It doesn’t matter unless he reports the problem again and then it will be a trend and not a one-off quirk.

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