Previously, we developed Power over Ethernet technology in our switches only in the direction of increasing transmitted power. But during the operation of solutions with PoE and PoE+, it became obvious that this was not enough. Our clients are faced not only with a lack of energy budget, but also with a standard limitation of Ethernet networks - an information transmission range of 100 m. In this article we will tell you how to get around this limitation and test long range PoE in practice.
Why do we need PoE long range technology?
A distance of a hundred meters is a lot. Moreover, in reality the cable is never laid in a straight line: you need to go around all the bends of the building, rise or fall from one cable channel to another, and so on. Even in medium-sized buildings, the limitation on the length of an Ethernet segment can turn into a headache for the administrator.
We decided to use the example of a school building to clearly demonstrate which devices will be able to receive electricity using PoE and connect to the network (green stars), and which will not (red stars). If network equipment cannot be installed between the cases, then at the extreme points the devices will not be able to connect:
To bypass the range limitation, Long Range PoE technology is used: it allows you to expand the coverage area of ββthe wired network and connect subscribers located at a distance of up to 250 meters. When using Long Range PoE, data and electricity are transferred in two ways:
- If the interface speed is 10 Mbps (regular Ethernet), then simultaneous transmission of both energy and data is possible on segments up to 250 meters long.
- If the interface speed is set to 100 Mbps (for models TL-SL1218MP and TL-SG1218MPE) or 1 Gbps (for model TL-SG1218MPE), then no data transfer will occur - only energy transfer. In this case, some other way to transmit data will be required, for example, a parallel optical line. Long Range PoE in this case will only be used for remote power.
Thus, when using Long Range PoE on the territory of the same school, network equipment that supports a speed of 10 Mbps can be located at any point.
What switches that support Long Range PoE can do
The Long Range PoE function is available on two switches in the TP-Link line: ΠΈ .
TL-SL1218MP is an unmanaged switch. It has 16 ports, its total PoE budget is 192 W, which allows it to supply power up to 30 W per port. If the power budget is not exceeded, all 16 Fast Ethernet ports can receive power.
Configuration is carried out using switches on the front panel: one activates the Long Range PoE mode, and the second configures the priority of ports when distributing the switchβs energy budget.
TL-SG1218MPE belongs to Easy Smart switches. You can manage the device via the web interface or specialized utilities.
In the System interface section, administrators have access to standard routine operations: changing the login and password for the administrator account, setting the IP address of the control module, updating the firmware, and so on.
Port operating modes are set in the Switching β Port Setting section. Using the remaining tabs of the section, you can enable/disable IGMP and combine physical interfaces into groups.
The Monitoring section provides statistical information about the operation of the switch ports. You can also mirror traffic, enable or disable loop protection, and run the built-in cable tester.
The TL-SG1218MPE switch supports several virtual network modes: 802.1q tagging, port-based VLAN, and MTU VLAN. When operating in MTU VLAN mode, the switch only allows traffic exchange between user ports and the uplink interface, that is, traffic exchange between user ports is directly prohibited. This technology is also called Asymmetric VLAN or Private VLAN. It is used to improve network security so that when physically connected to the switch, an attacker will not be able to seize control of the equipment.
In the QoS section, you can set interface priority, configure user traffic speed limits, and deal with storms.
In the PoE Config section, the administrator can forcefully limit the maximum power available to a particular consumer, set the energy priority of the interface, connect or disconnect the consumer.
Testing Long Range
On the TL-SL1218MP we have enabled Long Range support for the first eight ports. Our test IP phone worked successfully. Through the phone settings, we found out that the agreed speed is 10 Mbps. We then turned the Long Range PoE switch to Off and checked what happened to the test phone after that. The device booted successfully and reported using the 100 Mbps mode on its network interface, but data was not transmitted through the channel and the phone was not registered with the station. Thus, powering consumers connected over long Ethernet channels is possible without activating the Long Range PoE mode, but in this case only power will be transmitted through the channel, not data.
In standard power over Ethernet mode (when the segment length does not exceed 100 meters), energy and data transfer occurs at speeds up to 1 Gbps inclusive. Testing the operation of a telephone powered by PoE and connected with a cable of maximum length was successful.
On the TL-SG1218MPE switch we switched the port to 10 Mbps Half Duplex mode - the device connected successfully.
Naturally, we wanted to know how much energy the phone consumes with this connection, it turned out that it was only 1,6 W.
C:>ping -t 192.168.1.10
Pinging 192.168.1.10 with 32 bytes of data:
Reply from 192.168.1.10: bytes=32 time<1ms TTL=64
Reply from 192.168.1.10: bytes=32 time<1ms TTL=64
Reply from 192.168.1.10: bytes=32 time<1ms TTL=64
Reply from 192.168.1.10: bytes=32 time<1ms TTL=64
Reply from 192.168.1.10: bytes=32 time<1ms TTL=64
Reply from 192.168.1.10: bytes=32 time<1ms TTL=64
Reply from 192.168.1.10: bytes=32 time<1ms TTL=64
Reply from 192.168.1.10: bytes=32 time<1ms TTL=64
Reply from 192.168.1.10: bytes=32 time<1ms TTL=64
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Ping statistics for 192.168.1.10:
Packets: Sent = 16, Received = 9, Lost = 7 (43% loss),
Approximate round trip times in milli-seconds:
Minimum = 0ms, Maximum = 0ms, Average = 0ms
Control-C
But if you switch the switch interface to 100 Mbps Half Duplex or 100 Mbps Full Duplex operating mode, the connection with the phone is immediately lost and is not restored.
The interface itself is in the Link Down state.
Almost the same thing happens if the interface is switched to automatic speed and duplex negotiation mode. Therefore, the only way to use such long Ethernet segments is to manually set the connection speed to 10 Mbps.
Unfortunately, such long cable segments are not detected by the built-in cable tester.
Updating other PoE switches
Since the number of devices powered by PoE is constantly increasing, we have updated the power supplies of older models. Now, instead of 110 W and 192 W power supplies, all models will have 150 W and 250 W units. All these changes can be seen in the table:
As PoE technology began to penetrate the consumer level, another change in the lineup was the introduction of switches designed for small offices and home use.
In 2019, models appeared in the line of unmanaged Fast Ethernet switches ΠΈ for 5 and 8 ports. The power budget of the models is 58 W, and it can be distributed among four interfaces (up to 15,4 W per port). The switches do not have fans; they can be placed directly in office and work spaces, apartments and used to connect any IP cameras and IP phones. Switches can prioritize power distribution: when overload occurs, low-priority devices are turned off.
Models ΠΈ , like the SF models, are designed for desktop installation, but they have a built-in gigabit switch, which allows you to connect high-speed terminal equipment that supports 802.3af.
Switch Can be placed both on a table and in a rack. This model has eight Gigabit Ethernet ports, each of which can be connected to a consumer with IEEE 802.3af/at support and a power of up to 30 W. The total energy budget of the device is 126 W. A special feature of the switch is that it supports a power saving mode, in which the switch periodically pings its ports and turns off the power if there is no connected device. This allows you to reduce energy consumption by 75%.
In addition to the TL-SG1218PE, the TP-Link line of managed switches includes models ΠΈ . They have the same total energy budget of the device - 55 W. This budget can be distributed among four ports with an output power of up to 15,4 W per port. These switches have the same firmware as the TL-SG1218PE, respectively, and the functions are the same: network monitoring, traffic prioritization, QoS, MTU VLAN.
A complete description of the TP-Link PoE device range is available at .
Source: habr.com