RouterOS PoE Priority Settings

What it is

PoE priority decides which powered devices stay on when the switch has less power than the devices need.

A switch has a limited power supply. Every PoE device draws from it. If the total demand rises above the budget, something has to give, and priority tells the switch what.

Without priority, you would not know which device the switch turns off. With priority, you decide in advance.

How it works

Each port has a priority value, and the switch uses it when power runs short.

The power budget

The budget is the power that the supply can give to all PoE ports together.

It depends on the power supply that you connect, and on the model. A switch with eight PoE ports may not be able to give full power to all eight at once. That is normal, because most devices draw less than the maximum.

Devices draw different amounts over time. An access point uses more when its radios are busy, and a camera with a heater uses more in winter. A budget that works in summer can fail in winter.

The priority setting

Every PoE out port has a poe-priority value.

/interface ethernet poe set ether2 poe-priority=10
/interface ethernet poe set ether3 poe-priority=20
/interface ethernet poe print

A lower number means a higher priority. In this example, ether2 has a higher priority than ether3. When the budget runs out, the switch keeps ether2 powered and turns off ports with lower priority first.

What happens at the limit

The switch protects itself, not the devices.

If a port with a better priority needs power and none is left, ports with a worse priority are cut. When power becomes available again, the ports can come back. A device that loses power restarts when it gets power back, so users see a short outage.

The exact behaviour depends on the model, including how ports with equal values are treated and how fast they return. Do not rely on a tie. Give each important port its own distinct value.

Planning a power budget

Work through the budget before you install.

1. List the devices on each switch and their maximum power draw.
2. Add the maximum values, and compare the total with the budget.
3. If the sum is above the budget, decide which devices to protect.
4. Set the priorities to match, and keep a margin for cold weather.

If you add devices later, repeat the work. A small change can push the total over the limit.

A maximum power setting

Some models also let you limit how much power a port or the whole switch may supply.

A limit on a port protects the switch from a faulty device that draws too much. A limit on the total can keep a switch within the capacity of a small power supply. Availability depends on the model, so check the documentation.

Priority is not the same as monitoring

Priority acts only at the moment of shortage.

It does not tell you that a shortage happened. To find out, you need to look at the port status and the logs, which the next page covers.

Checking

/interface ethernet poe print
/interface ethernet poe monitor ether2

If a device keeps restarting, compare the poe-priority of its port with the others, and look at the status of the port.