PoE (Power over Ethernet) has become such a commonplace technology that it is easy to take for granted. If we connect a phone, access point, security camera, card scanner, or other PoE-enabled device to a port that supports power, we expect to see lights and activity. Plug and play right?
What happens though when there is a problem with PoE? Is enough power being sent to a given port to properly power a variety of end devices with different voltage requirements? Shouldn’t we test it just like we do the network before we connect devices that support business-critical applications and services?
In most environments, technicians “test” PoE by connecting the powered device (PD). If it powers up they move on to the next connection. If not, they conclude that PoE doesn’t work and jump into the switch configuration. However, just because a device doesn’t light up doesn’t mean that PoE is disabled or not working at all. It may be that the link is simply not providing enough juice to power up the device.
It is up to the technician to troubleshoot whether there is a configuration problem in the switch, a cable issue, or if power is being sent at all. The first two things can be accomplished using a laptop (if it even has an RJ45 port) and a basic cable tester. The latter though is a little more difficult. Most laptops and cable testers do not have the capability to test the actual voltage level being sent to a port to run a given powered device.
Troubleshoot and Validate PoE
The LinkSprinter is a pocket-sized tool that will tell you in 10 seconds if proper power is being provided (as well as thoroughly test the network link), and report the amount of voltage at the wall jack. Key point – The amount of power coming out of the switch port (the “PSE” or power sourcing equipment) itself will be stronger than the actual power at the wall jack where the powered device sits. This is because power will dissipate as it travels down the wire and it is therefore essential that PoE voltage be tested at the edge of the network where the powered device sits and not tested directly at the switch port.
When provisioning the switch for the various PoE devices it must provide power to, it is important to calculate the overall power requirement or “power budget” for all devices you are planning to connect to a given switch. The next step is to validate that the switch is capable of providing that amount of power output to each device. It’s also a good idea to document what’s connected to each switch port to make troubleshooting easier as well as moves, adds, and changes down the road.
Common PoE Issues to watch out for
- PoE is subject to the same distance limitations as standard network cable runs – 100m/328ft
- Incompatibility between powered device (PD) and power sourcing equipment (PSE)
- Switch power budget over-subscribed
- Switch provisioning of PoE
- Power limited per port
- Cable faults
You’re already plugged into the wall jack, why not get even more connectivity validation done in one test… In addition to validating PoE, LinkSprinter’s automated test will validate the entire connection path including the physical layer, link speed, switch connectivity, DHCP server function (can configure static IP if needed), gateway availability, and ultimately, can get to a target destination in the cloud such as www.google.com from that wall jack.
Team collaboration, documentation, and test results with Link Live™
At the completion of each test, LinkSprinter automatically sends your test results to the free and included Link-Live collaboration, reporting, and analysis platform. You now have a documented record of connectivity from each wall jack including switch slot/port/VLAN detail. These test results can also be e-mailed to you to be viewed on your own mobile device. You can reply to the e-mail or comment on your mobile device with the wall jack location or other important information that helps you to identify the complete connection path. You can even attach photos for each test. This might include an image of the wall jack or device or could be an image of the serial number or asset tag.
Additional points to consider:
- LinkSprinter can run off of PoE so no need to worry about battery life.
- Most access point connections are installed in or near ceilings, where it can be awkward (if not dangerous) to test with a laptop. The LinkSprinter fits easily into the palm of your hand, making it easy to slip into hard-to-test areas.
- If a more detailed PoE test is required, consider LinkRunner AT. LinkRunner AT not only reports the level of voltage at the wall jack but also reports on what class of PoE is configured and is capable of drawing a 25W load – what we call the TruePower™ test – to measure power, not just voltage (which is common with lesser quality PoE testers.
LinkSprinter Makes Problem Isolation Simple
Instead of guessing at the issue when the lights on the PoE device are dark, technicians can test and validate PoE before connecting phones, access points, or anything else that runs on this amazing, simple, and critical technology.
Download our PoE Reference poster as a quick guide for powered devices.
