Power over Ethernet (PoE) is one of the most useful and convenient mechanisms in modern networking. Devices that require an Ethernet connection can also draw power through Ethernet lines, as long as they’re connected to a PoE ecosystem. This saves time, money, and hassle on running power lines or designing around available outlets.
So, if you are considering working PoE into a network, then there are a few things you’ll need to learn. One such lesson is the distinction between active and passive PoE. Both exist, but they are not universally swappable options. Take a minute to learn more about each type of PoE, and you’ll be able to make the right choice for your network.
What Is an Active PoE Switch?
Let’s look into active PoE first. This is the most common form of PoE, and it’s baked into the IEEE 802.3af, 802.3at, and 802.3bt standards. Generally speaking, if you shop for PoE, you are shopping for active PoE. You have to specifically look for passive designs to get away from these standards.
The reason active PoE is the standard is that the “active” part of the system actually tests the endpoint devices in the network to ensure electrical power compatibility. This includes testing whether or not the device needs power and what voltage is appropriate for the device.
If there is a compatibility problem, the active switch can deny power to that device to prevent potential damage and other problems.
When Should You Use Active PoE?
Since active PoE is the gold standard, it’s the preferred choice in most cases. Most networks that use power over Ethernet, such as camera systems, remote monitoring, and PoE wireless access points, are better managed by active PoE.
On top of that, any system that uses hybrid equipment (meaning some devices draw power over Ethernet while others don’t) should exclusively utilize active switches. The active design is most important in these cases as non-PoE devices can be damaged by power delivery through Ethernet cables.
What Is a Passive PoE Switch?
Considering the meaning of “active” it’s not hard to guess what constitutes a passive PoE switch. Such a switch still delivers power over Ethernet lines to endpoint devices, but the active checking feature is absent from this kind of equipment.
This means that power just passes through the passive switches by default. If the switch has power, then it sends power along to the endpoint devices.
This comes with a clear pro and a clear con.
On the pro side, passive PoE switches are much less complicated in terms of hardware and design, and they almost always cost less as a consequence.
On the downside, these switches come with a specific risk. If you plug in a device that is not designed for PoE, then the current delivered through the Ethernet line can burn and damage that device.
Common Use Cases for Passive PoE
Considering the risk and non-standard nature of passive PoE, when is it best used?
Really, it’s not often the best choice. Passive PoE is largely being phased out because active switches can compete with passive switch costs while providing extra benefits.
The only real use case for passive PoE is in legacy systems that require it. Some endpoint devices are designed for specific passive PoE setups, and they might use proprietary or specific injectors and/or adaptors for Ethernet and power. If you are using such devices, then sourcing the appropriate passive PoE switches for them is probably more cost-effective than converting all of your equipment to standard PoE injectors and functions.
How to Choose Between Active and Passive PoE
Sometimes, choosing the right networking equipment is extremely challenging. When it comes to active and passive PoE, the choice largely makes itself.
In the vast majority of cases, active PoE is the superior option. Because it’s the standard, it’s easier to find and you have a lot more equipment options. It is also much easier to implement because you don’t have to worry about burning out your non-PoE devices.
Passive switches can save money in specialized networks where all of your endpoint devices are already compatible.
But, any network that mixes and matches various PoE and non-PoE endpoints should stick with active PoE.
Additional Learning Center Resources
- Benefits of Cisco 9000 Series Switches
- Best Way to Connect Multiple Switches
- Should I upgrade from 3750X switch to the 3850 switch?
- Cisco Catalyst Switches Product Guide
- Basics of Network Switches
- What are the Differences between Cisco 3650 and 3750X Switches?
- What does 5G mean for my business network?
- How to Choose The Right Rackmount Server
