PoE budgets and switch selection: classes, allocation, power supplies and cabling
For network and low-voltage technicians who know the PoE standards and can add up a simple budget, and now need to size and choose switches for mixed loads of phones, access points, cameras and four-pair devices. It builds on 'Power over Ethernet (PoE)' and 'IP cameras and PoE power budgets'. You'll calculate allocations by class and by negotiated power, choose a switch and power-supply configuration that covers both total budget and per-port needs, plan which ports lose power first when supplies fail, diagnose a device that won't power up from the negotiation stages, and check the cabling factors that matter at 60–90 W. Examples use Cisco's published configuration guide and data sheet; other vendors use different command names and budgets, so always read your switch's own documentation. Electrical code requirements for cable bundles depend on where you work; follow your local code and your electrician. Ends with a supervisor-graded switch sizing exercise.
- Level
- Intermediate
- Length
- About 110 minutes
- Contents
- 5 lessons · final exam
- Status
- Published · updated 10 Oct 2026
Skills you'll practise
- Calculate the PoE power a set of devices needs from their classes and the switch's allocation method
- Choose a switch model and power-supply configuration whose PoE budget and port types cover the load with headroom
- Identify which ports lose power first when the budget runs short, and configure port modes and limits to protect critical devices
- Explain how detection, classification and LLDP negotiation decide whether a device powers up
- Identify cabling factors (bundle heating, DC resistance unbalance) that affect four-pair PoE
Course outline
- 1.Calculate the PoE power a set of devices needsLesson · 25 min
- 2.Choose a switch model and power-supply configurationLesson · 20 min
- 3.Identify which ports lose power first and protect critical devicesLesson · 20 min
- 4.Explain how detection, classification and negotiation decide whether a device powers upLesson · 20 min
- 5.Identify cabling factors that affect four-pair PoELesson · 10 min
- 6.PoE budgets and switch selection: classes, allocation, power supplies and cabling: knowledge checkKnowledge check · 15 questions
- 7.PoE budgets and switch selection: classes, allocation, power supplies and cabling: practical exerciseKnowledge check · 1 question
- 8.Final exam10 questions · passing it completes the course, so people who already know the material can test out
Sources it draws on
The lessons and questions are written from these references, so learners can go back to the original.
- Cisco Catalyst 9300 Series configuration guide (IOS XE 17.9): Configuring PoE (classes, auto/static/never modes, power denial order)
- Cisco Catalyst 9200 Series Switches Data Sheet (PoE budgets by model and power supply, Perpetual and Fast PoE)
- IEEE SA: IEEE 802.3bt-2018, Power over Ethernet over 4 pairs (amendment to IEEE 802.3)
- Fluke Networks: What is PoE Negotiation? (June 2025)
- Fluke Networks: PoE load testing and troubleshooting (July 2021)
- Fluke Networks: Upgrading to four-pair PoE: what you need to know (May 2018)
- Fluke Networks: To bundle or not to bundle (PoE heat rise) (February 2019)
- Fluke Networks: DC Resistance Unbalance Testing – What You Need to Know (May 2025)
See it with your own jobs and topics
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