This article is using the new suggested format "short and to the point."
In this example, I take a look and DNS troubleshooting and use Wireshark as well as NSLOOKUP to troubleshoot a DNS issue.
In this video you will see how I used Wireshark to quickly identify that the current DNS server is having an issue and how I quickly compared it against Google’s public DNS server.
When you work with equipment that isn’t close by, you need to develop an awareness of what the various color and blinking lights mean.
For those of you who find this trivial haven’t had to walk someone through an install or troubleshooting episode from 1,000 miles away, or across town.
I encourage technicians to develop this skill since they will encounter this challenge sooner or later.
Not only should you be aware (and document) what the various color and blinking combination means, but how the lights react to various scenarios. For example, bootup, firmware update, indicator that the device can get to the internet, etc.
In this video, I show you one of many ways to measure the boot up time of a router that I was shipping out. I’m sure you will figure your own way or doing this, if you don’t already have one.
I’m always going on about learning how to use your tools properly so heres a great example of that.
For those of you who have read my articles or seen my videos about packet slicing, you probably wonder "how easy is it to set the snaplen back to its default ?"
One obvious answer is to jot down the default value and the other one is simply to type the number 1, and then press the up arrow key.
Enjoy
Before I start, I want to acknowledge a few things:
- Yes, there are utilities out there that can do this
- Yes, you can look at DNS response time in the Statistics->DNS report
- Yes, you can graph this in Wireshark’s IO graph
There a lot of benefits of doing it this way since you can customize your charts, which may not be possible with the other options and you get a better understanding of what you are reporting.
In the video, I start at the command prompt with nslookup, move on Wireshark covering capture filter, adding a column, creating a display filter and then exporting the trace to be used by Excel.
As I mentioned in the video this technique can be used with all sorts of other protocols when troubleshooting or documenting performance.
My ISP has been pestering me lately, claiming that my equipment is outdated, and I am not taking full advantage of the higher data rates available on my current Internet plan. I was skeptical, as always, that this was another ploy to sell me less for more – just how bad could my 14-year-old modem/router really be? I finally caved in, and on a recent Friday morning I told my wife that our Internet would be down for about an hour while I set about installing the new WiFi mesh system.
When I called the ISP’s 800 number to register the new equipment, I sent them a screen shot with Model, Serial Number and MAC address for the modem to avoid errors. It took several attempts before they claimed victory. They had found my box, the install would soon be complete, and we would be connected to the world once again. Except that we weren’t.
Assuming that the Internet coax was now live, I turned next to tech support for the new hardware. Those of us who have done these installs understand that each step begins with the warning “this process may take a while.” After a lengthy online session with hardware tech support, they finally concluded that the problem must be with the ISP. I was about to explain why that could not be true when the “outage” notice arrived on my phone. The estimated time to restore service was 4:20 pm – then 7:20 pm – then 11:20 pm. When I awoke the next morning, there was another message, confirmed by my neighbor, that the Internet service had been restored.
The ISP, which by now had taken a lot of heat for the lengthy outage, dispatched a technician to our home. After another hour or so of plugging, unplugging and sharing dog stories while staring at blinking lights, the technician called tech support, and the two of them finally found the problem – the MAC address (a series of 6 pairs of hex characters separated by colons) was supposed to end in “B” but had somehow been entered as “E”. The “E” address was the router, which the ISP could identify, but not ping. Of all the things that have to work together for a functioning home Internet, it only took one small “E” to bring down the system.
As dependent as we are on keyboards and screens, it is a small wonder that this type of “typo” hasn’t caused more problems. Typos actually have quite a history of impactful effects.
In the 17th century (long before keyboards, when type was set by hand) about 1,000 copies of the King James Bible were printed with the Seventh Commandment as “Thou Shalt Commit Adultery.” Many readers were pleasantly surprised by the omission of “not,” but King Charles was not amused. He successfully destroyed all but about 20 copies, which are now coveted collectors' items. The long-term impact of what is now known as the “Sinners Bible” is not recorded.
On July 22, 1962, just minutes after the launch of the Mariner 1 spacecraft mission to Venus, the rocket was destroyed because it was deviating from the planned course. Initial reporting blamed a missing “-“ in the software coding, while NASA later said a diacritical for the symbol R in an equation had been omitted. Regardless of the cause, the mistake cost around $180 million in today’s dollars. Science Fiction author Arthur C. Clarke called it “the most expensive hyphen in history.”
Prior to the dedication of the Lincoln Memorial in 1922, a critical typo was discovered in the engraving of Lincoln’s Second Inaugural Address – a sharp observer noted that the phrase “WITH HIGH HOPE FOR THE EUTURE” (sic) made no sense. It was corrected by filling in the bottom of the letter “E” to make an “F.” The mistake is still visible to this day. Google the word “euture” for details.
In 1996, Google co-founders Larry Page and Sergey Brin were pondering a name for their new search engine. Thankfully, they moved on from their first choice (“BackRub”) to Googol (short for the number one followed by 100 zeroes). A colleague checked the availability of that domain name, but mis-typed it as “google.com.” The name of the world’s most popular search engine began with a typo.
The letter “E” is a factor in many typos, which is not surprising given it is the most common letter in the English language. This brings to mind an adage with disputed origins that has often been attributed to aerospace engineer Edward A. Murphy. The phrase arose from an accident involving rocket sled testing around 1949. Murphy’s original comment was “If there are two or more ways to do something and one of those results in a catastrophe, then someone will do it that way.” At a post-incident press conference, John Stapp – head of the test project – summarized his presentation with the succinct and now commonplace “Anything that can go wrong, will go wrong.”
Computers and keyboards are now commonplace. The power of even one typo is worth considering before taking the risk of hitting “Enter”.
Author Profile - Paul W. Smith - leader, educator, technologist, writer - has a lifelong interest in the countless ways that technology changes the course of our journey through life. In addition to being a regular contributor to NetworkDataPedia, he maintains the website Technology for the Journey and occasionally writes for Blogcritics. Paul has over 50 years of experience in research and advanced development for companies ranging from small startups to industry leaders. His other passion is teaching - he is a former Adjunct Professor of Mechanical Engineering at the Colorado School of Mines. Paul holds a doctorate in Applied Mechanics from the California Institute of Technology, as well as Bachelor’s and Master’s Degrees in Mechanical Engineering from the University of California, Santa Barbara.
