COVID-19 forced an overnight shift upon us which facilitated a world-wide “work from home” for as many employees as deemed necessary and feasible. The initial hurdle for each IT department was to set up the basics to enable employees to get their work done – VPN tunneling was among them. …
There are a few open-source and free tools out there that can help visualize the path traversed between two hosts. We’ve talked about mtr and traceroute, and recently I came across Dublin traceroute. Actually, the inventor of Dublin traceroute maintains his own blog here, and there you can find many…
We have talked about how to use nmap to detect the OS of a remote host. Nmap does that by sending probing packets and depending on the responses may or may not be able to identify the remote OS with a certain accuracy. That can work well in many cases,…
There are multiple ways to get a file from a remote Linux host. To name a few: scp, sftp, tftp, http/https… And you could probably add more in the list. Depending on your requirements in terms of security, ease of use, availability, and set-up effort you have to decide what…
mtr stands for “My Traceroute” and, in a nutshell, it’s traceroute on steroids. They both work the same way: a host sends probing packets to routers, measures and reports latency and packet loss. mtr takes that to the next level by giving you the ability to run the probe packets…
We have talked about the differences between iPerf2 and iPerf3 in terms of their reverse options. I recently noticed that the latest iPerf3 version 3.7 released on 06/21/2019 has an additional option to handle reverse testing, and I wanted to talk about it. Installation It takes a while for a…
When working on subnet addressing, we often have to look up and double-verify any address we deal with. Some of you have been doing this for so long that you can make all these calculations off the top of your head. But for most of us, it’s a cumbersome and…
We have already discussed packet analysis with tcpdump but will dive deeper in this post! Tcpdump is probably the most popular and capable tool that allows you to dig down to all the bits and bytes of network traffic, including TCP flags. Ngrep, stands for “network grep,” and like its cousin, the…
Let’s consider the following scenario: you have a Linux host that has more than one network interface, both are routable and both are up and running. How do you determine which interface or route is used when trying to reach another host? In other words the routing table looks like…
This is the last of four posts related to dnsmasq; it covers the basics on how to set up your own DHCP server on your network. For reference, here are the previous dnsmasq posts on DNS caching, a read-only TFPT server, and DNS server. Set Up To install dnsmasq you…
