Newsletter #34 - Subnets Jun 28 2021

Hello, and welcome to issue #34!

I haven't been able to write much lately, but I'm still around. I've continued learning and exploring different technologies. In the last few months, I've spent some time doing DevOps work in AWS, helping write some Python Azure functions and even some Apex development. As you can tell, all over the place. But most of all, surviving the rainy season in Central America.

As part of my work, I had to design a client's network. And because I love doing networking stuff, and I wanted to refresh my knowledge of subnetting. I ended up creating a subnetting Calculator. You can find it here:

The source code here:

You might know how much trouble I have naming things (a lot!). I was going to call it rdCIDR. But when I was about to create the repository, I thought it was funny that it was almost a palindrome. Almost, missing an i there. So I thought, well, add the missing i, and if someone asks me "why?" I'll say it stands for Interactive. And that's the story behind the weird name.

This tool, like many other tools and projects I start, was not going to be public. I didn't want to invest much time polishing the code to make it presentable. But then I thought it might help someone understand subnetting. And in my HardDrive, it'll just be forgotten and never see the light of day. So I decided to put it out.

I know the codebase needs more work, but that doesn't mean it is not useful or could be exactly what someone else needs to understand a concept they were struggling with. So now, I think I'll be sharing more of the tools and projects I create, even if they are not complete.

And you know feedback is always welcomed. And it's always nice getting an email from someone that enjoyed one of my articles or tools.

Recommendations and interesting topics

You probably heard about Unix and how it has influenced many, if not all, our modern operating systems. Well, Unix was influenced by Multics.

"The design and features of Multics greatly influenced the Unix operating system, which was originally written by two Multics programmers, Ken Thompson and Dennis Ritchie."(source: wikipedia)

My recommendation this week is the site It is full of history, old Develper Documentation, source code, and much more. I believe you'll enjoy it. I encourage you to explore the site. The dates section is a fun one to read, and also the myths section.

Also, I have a podcast recommendation for you. It is a different type of podcast, more like a full-cast audio series, with excellent storytelling. And it is science fiction, so what else could you ask for:

Qcode Media - From Now

They have other podcasts if you want to explore their shows.

Ok, that's it for this edition of the newsletter. I hope you are doing well where ever you are.

If you have any interesting articles, books, podcasts, or any other feedback, you can email me or join the Discord server. I'm always on the lookout for interesting stuff.

Until next time, Derik

Tip of the week

Have you ever wanted to create an SSH tunnel, but you always forget which flags to pass? It happens to me all the time. Fear not, my dear friend, ~/.ssh/config to the rescue. Imagine you want to map your local computer's RDP port(3389) to another IP only accessible by a Bastion host. You could add the following to your ~/.ssh/config:

Host some-name-bastion-rdp
  IdentityFile ~/.ssh/id_mySecretKey.key
  IdentitiesOnly yes
  User the-user-in-the-bastion
  LocalForward 3389

With that configuration, you don't have to use the easy to forget command:

ssh -L 3389:

You can use:

ssh some-name-bastion-rdp

And ta-da! the tunnel is created, and you can RDP to your heart's content. I used RDP, but you get the idea you can use any other port.

** If you want to check what else I'm currently doing, be sure to follow me on twitter @rderik or subscribe to the newsletter. If you want to send me a direct message, you can send it to