300-425 · Question #24
An engineer is designing the physical infrastructure for an IEEE 802.11ac network. Which power design should the engineer use?
The correct answer is A. 802.3at PoE+ ports. IEEE 802.11ac access points require more power than 802.3af can supply, making 802.3at PoE+ the correct power standard for this deployment.
Question
An engineer is designing the physical infrastructure for an IEEE 802.11ac network. Which power design should the engineer use?
Options
- A802.3at PoE+ ports
- Binline PoE ports
- C802.3af PoE ports
- D802.3af PoE injectors
How the community answered
(56 responses)- A86% (48)
- B2% (1)
- C5% (3)
- D7% (4)
Why each option
IEEE 802.11ac access points require more power than 802.3af can supply, making 802.3at PoE+ the correct power standard for this deployment.
IEEE 802.3at PoE+ delivers up to 30W per port, which meets the higher power requirements of 802.11ac APs (commonly 20-25W for Wave 1 and up to 30W for Wave 2 with MU-MIMO radios and additional features like USB and BLE), ensuring stable operation without underpowering the device.
Inline PoE is not a recognized IEEE standard designation and does not guarantee the wattage output required by 802.11ac APs.
IEEE 802.3af provides a maximum of 15.4W (12.95W usable at the device), which is insufficient for the power demands of most 802.11ac access points.
802.3af PoE injectors are still limited to 15.4W output; using an injector does not change the power budget and remains inadequate for 802.11ac APs.
Concept tested: PoE standard selection for 802.11ac APs
Source: https://www.cisco.com/c/en/us/products/collateral/wireless/aironet-3700-series/data_sheet_c78-729488.html
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