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.
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.
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.
Just kidding, it's not... But fear not and read on!
You can find a Russian translation of this article here.
Working with containers always feels like magic. In a good way for those who understand the internals and in a terrifying - for those who don't. Luckily, we've been looking under the hood of the containerization technology for quite some time already and even managed to uncover that containers are just isolated and restricted Linux processes, that images aren't really needed to run containers, and on the contrary - to build an image we need to run some containers.
Now comes a time to tackle the container networking problem. Or, more precisely, a single-host container networking problem. In this article, we are going to answer the following questions:
While answering these questions, we'll setup a container networking from scratch using standard Linux tools. As a result, it'll become apparent that the single-host container networking is nothing more than a simple combination of the well-known Linux facilities:
And for better or worse, no code is required to make the networking magic happen...
Not every container has an operating system inside, but every one of them needs your Linux kernel.
Before going any further it's important to understand the difference between a kernel, an operating system, and a distribution.
To be technically accurate, the title of this article should have sounded something like Does container image have a whole Linux distribution inside? But I find this wording a bit boring for a title 🤪
