Introduction

What this chapter covers

The Introduction sets the base for every later chapter by explaining how Ethernet switching works on MikroTik devices.

It starts with the general rules of Layer 2 forwarding. It then shows where that forwarding happens on a MikroTik device: in the CPU through a bridge, or in a switch chip.

The chapter has one syllabus topic with several sub points, and two pages cover all of them.

You do not need to memorise device model numbers. You do need to know which family of device uses which method, because later chapters configure VLANs, filters, limits and security in different places depending on that answer.

The topics are listed here in the order the syllabus gives them:

• Unicast, multicast and broadcast traffic.
• MAC learning in bridges and switches.
• Interface settings.
• The RouterOS bridge.
• The RouterBOARD switch chip, in its basic form and in the advanced CRS form.
• A brief look at SwOS.

How the topics fit together

The first page explains the rules, and the second page explains the hardware that applies them.

Learning, flooding and the three traffic types are the same everywhere. What changes between devices is who does the work, and which features are still available once the chip takes over.

How to use these pages

Each topic page has the same shape, so you can skim for what you need.

• What it is: the idea in plain words.
• How it works: the mechanism, with diagrams and example commands.
• What to remember for the exam: the facts to memorise.
• Common mistakes: the classic traps.
• Check yourself: three questions to test your understanding.

Try the console commands on a lab device or a virtual router. Print the bridge host table while pinging between two hosts, and watch entries appear and age out.