This learning path will teach you how to reproduce the most typical container networking setup: the Docker(-like) bridge network. Virtual bridge networks are extremely widespread - most Docker and Podman installations and many Kubernetes clusters (via the corresponding CNI plugin) use them to provide inter-container (or pod) communication within a single host. Understanding the underlying concepts of the bridge network is the key to efficiently troubleshooting container and Kubernetes networking issues.
You'll start with the basics, like creating a network namespace, and then move on to more complex topics, like connecting multiple network namespaces with veth pairs and a bridge device and using iptables to set up network address translation (NAT) and port publishing.
Follow along with a comprehensive tutorial, or start by solving hands-on challenges and come back to the tutorial when you get stuck. Any way you choose, by the end of this skill path, you'll gain a deep understanding of how container networking works under the hood.
Theory: How Bridge Container Networks Work
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This rather massive tutorial contains a comprehensive explanation of how a Docker bridge network
can be reproduced using common Linux command-line tools such as ip and iptables.
With a bottom-up approach, the tutorial starts with the basic concepts of Linux network namespaces and virtual Ethernet devices (veth pairs) and then moves on to illustrate the need for a "bridge" device to connect multiple network namespaces together and the involved routing and iptables rules.
It also covers the mechanisms of network address translation (NAT) and port forwarding,
so the next time you run docker run -p 8080:80 nginx, you'll know what exactly is going on under the hood.
However, this tutorial might be too much to digest at once. So, if you feel that you're getting lost in the details, you can always start with solving the skill path's challenges and come back to the individual sections of this tutorial when/if you get stuck.
🧙♂️ You shall not pass!
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