Everything you need to know about the PoE Switch

The PoE switch is an essential piece of network equipment in a local area network (LAN). Let’s first define the basic and important parts of the PoE switch, while examining its application in the network.

What is Power over Ethernet (PoE)?

Power over Ethernet is a technology that you can use to send data and power simultaneously over Ethernet cables. The power does not interfere with the data signals inside the Ethernet cable. Each cable has one RJ45 connector at both ends, and each connector has eight wires and eight pins that connect to the cables. As the cables send electrical signals, they create electromagnetic fields. The electromagnetic field from one pair of wires will affect the signals on the other wires, which is called crosstalk. Therefore, to avoid crosstalk, wires twist around each other in solid color and striped color pairs. Some of these twisted pairs are used for transmitting data, while others are used for receiving data. These twisted pairs come in two types: shielded twisted pairs (FTP) and unshielded twisted pairs (UTP/STP).

TP: Twisted Pair / U: Unshielded / F: Foil Shielding / S: Braided Shielding

Due to PoE sending current power, the cable must be copper, a length that is no longer than 100 meters, and Cat5e or better. What is Cat5e? Cat is the shortened form of “category” for copper cables, which defines the thickness of the wire, the number of pairs (2 pairs or 4 pairs), and how tightly each pair is twisted. Reference the table below to understand why the cable should be Cat5e or better. 

What is a network switch?

Network switches are communication devices in a local area network (LAN), connecting computers, printers, IP cameras, high-speed HD security cameras, tablets, VOIP phones, and wireless access points. Imagine a LAN without a switch, where all devices transmit and receive data simultaneously, many things occur, data could be lost, data could be sent to the wrong device, or there could be a very late arrival. To prevent this, the solution is to plug a network switch in the path of the devices, so the switch can transfer data between devices in an organized way.

What is a Power over Ethernet (PoE) switch?

A PoE switch is a type of network switch that supports PoE technology. When network equipment is connected to a PoE switch, the switch checks whether those devices are PoE compliant or not. If they are power devices (PDs), they will automatically power them. Devices that support PoE technology require different voltage levels. For example, low-voltage PoE devices include basic security cameras, tablets, VOIP phones, and wireless access points. High-voltage PoE devices include high-speed HD security cameras, LCDs, and laptops.

How does the PoE switch transfer data?

Imagine there are four printers in your local area network (LAN), and you want to send a print job to only one of these printers. How does your PC know where to send the data?                                               

Every device has its own address. In the LAN, each device has two addresses: a MAC address and an IP address. 

Media Access Control (MAC) address 

Media Access Control (MAC) addresses are layer 2 addresses. The manufacturer permanently assigns a MAC address, also known as the burned-in address. Therefore, it can’t be changed under any circumstance. The MAC address is used when devices need to communicate in the same local area network segment.

IP address 

IP addresses are layer 3 addresses, chosen by the network administrators. The IP addresses are also used when devices need to communicate with each other, allowing us to communicate with devices on a different LAN segment.

PoE switches are in layer 2 and use MAC addresses to transfer data between devices. With the print job message, you should add the MAC address of the printer. The message will first be sent to the PoE switch, where it will recognize the printer’s MAC address and send the message to that specific printer. 

When should we use a PoE switch?

If you only have one or two PoE power devices (PDs), the best option is to use the PoE media converters to supply power. These are small devices that are connected to a power source and plugged into power devices. 

These PoE media converters may be the more economical and space-saving solution. However, when you have too many power devices on your LAN, using a PoE switch becomes one of your priorities.

What are the advantages of using a PoE switch?

PoE switches have significant advantages. Since they cover both power and data, you only need one Ethernet cable for each device. This feature becomes more useful when you have a few power outlets and limited space for cables. With the help of these PoE switches, you can organize the cables.

PoE switch applications 

Below are the two most functional applications that can also be accomplished with both a compact PoE switch and RuggedNet industrial PoE switch:

Daisy-Chain and Ring Topology network application

Each RuggedNet switch connects to its neighboring switches via its uplink ports, eventually closing the ring. Using this network architecture—combined with ring protection protocols, such as Media Redundancy Protocol (MRP) or Rapid Spanning Tree Protocol (RSTP)—facilitates a highly resilient network that is required in mission-critical applications.

Dual Device Mode application

The Dual Device feature is extremely useful when two isolated network domains share a single network distribution location. The example below shows where a surveillance security (purple) network and a Wi-Fi (green) network are sharing a single hub distribution location. The two uplinks and the Dual Switch mode facilitates using a single PoE switch, driving both the cameras and the Wi-Fi access points, while maintaining isolation between the networks.

PoE switches come in various parts, each part having a significant role. How is the power sent through the Ethernet cable? Does the PoE switch have smart voltage-boosting technology? Should the PoE switch be managed or unmanaged? How many PoE switch ports do you need? These are the questions that come to mind at the next level. Each of these questions leads you to the product’s feature, where you can identify the specific parts of the PoE switches and determine which is best for your PDs and LAN. 

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