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As a software engineer, I need to deal with networking every now and then - be it configuring a SOHO network, setting up container networking, or troubleshooting connectivity between servers in a data center. The domain is pretty broad, and the terminology can get quite confusing quickly. This article is my layman's attempt to sort the basic things out with the minimum words and maximum drawings. The primary focus will be on the Data link layer (OSI L2) of wired networks where the Ethernet is the king nowadays. But I'll slightly touch upon its neighboring layers too.

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In Ethernet Lab - Broadcast domain we learned how to use switches (bridges) to merge multiple L2 segments into a single broadcast domain. In this lab, we'll see how to use the VLAN capabilities of a switch to split a single broadcast domain into multiple smaller domains.

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It's pretty common for an L2 segment to have a single IP subnet running atop. However, technically it's possible to configure multiple IP subnets over a single L2 broadcast domain. And although more complicated, configuring a single IP subnet over multiple disjoint L2 segments is also doable. In this lab, we'll cover the first two scenarios while the more advanced third case deserves its own lab - Proxy ARP.

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In Ethernet, all the nodes forming one L2 segment constitute a broadcast domain. Such nodes should be able to communicate using their L2 addresses (MAC) or by broadcasting frames. A broadcast domain is a logical division of a computer network. Multiple physical (L1) segments can be bridged to form a single broadcast domain. Multiple L2 segments can also be bridged to create a bigger broadcast domain.

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From time to time I use kind as a local Kubernetes playground. It's super-handy, real quick, and 100% disposable.

Up until recently, all the scenarios I've tested with kind were using public container images. However, a few days ago, I found myself in a situation where I needed to run a pod using an image that I had just built on my laptop.

One way of doing it would be pushing the image to a local or remote registry accessible from inside the kind Kubernetes cluster. However, kind still doesn't spin up a local registry out of the box (you can vote for the GitHub issue here) and I'm not a fan of sending stuff over the Internet without very good reasons.

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