Linux cron cheatsheet

 

Cool port reference guide

 

I know there are plenty more, but still very helpful

Flashback: Wireshark to Pivot Tables

 

Since my Excel Chart video, I've gotten a few requests on how to do this with a Pivot table.

So here it is.

Enjoy.

WIFI Testing - Know your Tools

 

The biggest challenge I face when training or troubleshooting WIFI is getting over that hurdle that “not all WIFI is equal”. It may sound silly and obvious at first but when you start paying attention you will see this misconception daily.

Quick example, client is complaining their wifi on their phone is slow but fine with their laptop. We could dissect this statement for hours but at a high level, lets start with some of the straightforward points; these 2 devices have different WIFI radios, antennae, drivers/operating systems, etc… So obviously it is not a fair comparison. Then we have to figure out if they are on the same band, what about channel widths, is MIMO and beamforming in play. As you can see the rabbit hole gets larger with each variable.

When performing a site survey for a client, they asked that I use their WIFI survey tool. I told them that wasn’t a problem but we need to recalibrate the tool for the device with the weakest radios so the coverage maps aren’t skewed or misleading. They didn’t quite understand why a phone, tablet computer and scanner would be any different.

I illustrated by running a simple iperf3 test using my phone and laptop. The laptop got twice as much throughput – up and down. I then briefly explained the concepts of antenna design, power management and RSSI/noise.

When I got back to the office I thought this would be a good topic to cover in an article.

Enjoy

Flashback: Using Wireshark's editcap to remove duplicate packets

 

As you get into capturing packets, you might find yourself in those scenarios where you end up with duplicate packets. It could be a result of your span config, location on your network, etc..

Here, I use Wiresharks editcap utility to remove duplicate packets