CWT Power over Ethernet (PoE) & Cabling Infrastructure

Question 1

Which IEEE standard originally defined Power over Ethernet (PoE), delivering up to 15.4W per port?

Accepted Answer

IEEE 802.3af

Answer

IEEE 802.3af was the first IEEE standard to define PoE, specifying up to 15.4W of power per port at the PSE.

Question 2

What is the maximum power output per port at the PSE specified by IEEE 802.3at (PoE+)?

Accepted Answer

30 watts

Answer

IEEE 802.3at (PoE+) doubled the original PoE power ceiling, specifying a maximum of 30W per port at the power sourcing equipment.

Question 3

Under IEEE 802.3af, what maximum power is guaranteed at the powered device (PD) after accounting for cable losses?

Accepted Answer

12.95 watts

Answer

After resistive losses in the cable, a PD is guaranteed a maximum of 12.95W, even though the PSE outputs up to 15.4W.

Question 4

Which device is used to add PoE capability to an existing non-PoE switch infrastructure?

Accepted Answer

PoE midspan injector

Answer

A PoE midspan injector sits between a non-PoE switch and the PD, injecting DC power onto the Ethernet cable without requiring a PoE-capable switch.

Question 5

What is the minimum recommended cable category for IEEE 802.3at (PoE+) installations?

Accepted Answer

CAT5e

Answer

CAT5e is the minimum recommended cabling for PoE+ deployments, providing adequate conductor gauge and insulation to minimize resistive power losses.

(CWT) Certified Wireless Technician Practice Test