Power over Ethernet (PoE)

What this chapter covers

The Power over Ethernet chapter explains how a MikroTik switch or router powers other devices through the data cable.

It covers three things in turn:

• The modes and standards, so you power a device safely.
• The priority settings, so you decide what stays on when power runs short.
• The monitoring commands, so you can see what is happening on each port.

Each of the three syllabus topics has its own page.

After this chapter you should be able to do the following:

• Name the two PoE standards and say what passive PoE is.
• Choose the right poe-out mode for a given device.
• Explain which priority value wins when the budget runs out.
• Read the monitor output and name the likely cause of a fault.

How the topics fit together

The three pages follow the life of a PoE installation.

You pick the mode when you connect a device. You set priorities when you plan the power budget of the whole switch. You use monitoring when something does not work, and also as a routine check.

A good habit is to treat the three as a loop. Monitoring shows how much power each device really draws, and that feeds back into the priority plan and into the choice of mode.

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.

If you have a PoE switch and a powered device, run the monitor command while you connect and remove the device. Watch the status change. Then change a priority value and read the print output, so you remember which direction is the higher priority.