why Power over Ethernet (PoE) is amazing!! // FREE CCNA // EP 12

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About this video

This CCNA episode (sponsored by Boson Software) explains Power over Ethernet: one Ethernet cable delivering both power and data. It began with Cisco IP phones — Cisco’s proprietary Inline Power arrived in 2000, sending power over the unused wire pairs (pins 4, 5, 7 and 8) — and the terminology is PSE (power sourcing equipment, typically the switch) and PD (powered device). Standardization followed: IEEE 802.3af in 2003 delivered 15.4 watts (Type 1); 802.3at in 2009, PoE+, doubled that to 30 watts (Type 2) and is the most common; Cisco’s proprietary UPoE in 2011 reached 60 watts using all four pairs, later standardized as 802.3bt (PoE++/4PPoE) Type 3 at 60 watts, with Type 4 in 2018 reaching 90 watts — enough for small computers, USB-C laptops, LED building lighting and even HVAC, not just phones, access points and cameras, and even switches powering other switches. The motivation is practical: one cable run instead of separate network and electrician-installed power, and devices can be moved easily. Active PoE negotiates the right wattage with the device using CDP (Cisco’s protocol) or the standard LLDP, and won’t power devices that don’t need it; passive PoE (often 24-volt, seen on some Ubiquiti gear) is always on and can fry non-PoE devices. In Cisco Packet Tracer and on a real switch he uses ‘show power inline’ to see total, used and remaining wattage and per-port draw, recounting phones that failed to power up when a switch’s power budget ran out, and noting some wattage is lost over the cable. He closes with a Boson practice-exam question: a device drawing more than its allocated power causes a syslog message and the port enters the error-disabled state.

Key takeaways

PoE puts power and data on one cable; the switch is the PSE, the device the PD
Standards climb: 802.3af 15.4W, 802.3at 30W, 802.3bt 60W (Type 3) and 90W (Type 4)
Active PoE negotiates wattage via CDP or LLDP; passive PoE is always-on and risky
One cable run removes the need for a separate electrician-installed power run
‘show power inline’ reveals the switch power budget and per-port draw

Episode details: published March 14, 2021 · 19:39 long. Summary written by Self Growth Videos from the episode itself. Business results and any income figures mentioned are NetworkChuck’s own claims, shared for education — they are not typical or guaranteed.

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