Linux Format



Almost every consumer networking appliance comes with a little power brick. For businesses with a busy network infrastruc­ture, all these power supplies add up to a lot of points of potential failure – and it’s not always convenient to deliver mains power to every location.

The solution is the Power over Ethernet standard. Actually, this is a collection of standards; the original PoE spec was published nearly 20 years ago as IEEE 802.3af-2003, but today the most popular variants are 802.3at-2009 and 802.3bt2018, aka PoE+ and PoE++.

The two systems work in the same way, allowing devices to be powered through a standard Ethernet socket, while sending and receiving data over the same cable. Any cable that conforms to Cat5 or greater can be used. PoE+ delivers up to 25.5W of power along with

Gigabit data speeds, while PoE++ can manage a maximum of 71.3W and is additional­ly compatible with 2.5GbE, 5GbE and 10GbE transmissi­on modes.

What makes PoE so versatile is that the power element is optional – almost every device that supports PoE also has a separate socket for a standard barrel plug, so you could also connect it to a regular Ethernet router or switch. For large offices, the solution is usually a switch with powered ports and a management interface that lets you track and control power consumptio­n.

For a small office or a home deployment, however, it may make more sense to invest in a PoE injector. This is a small, cheap, mains-powered box that simply forwards the network connection while adding power, so the downstream device can operate off a single cable.

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