Hardware and Software
This domain tests the physical and logical building blocks of a WLAN: access points, controllers, antennas, power, client adapters, and management software. Questions often ask which component performs a function or whether a PoE standard can power a given AP.
Infrastructure components
- An autonomous AP holds its own configuration. A controller-based AP is managed by a WLAN controller, which handles provisioning, firmware, RF management, roaming policy, and security. Cloud-managed APs move the controller function to a hosted service. APs can operate as root, bridge, repeater, or mesh nodes; a workgroup bridge attaches wired clients.
- Antennas shape coverage. An omnidirectional dipole radiates in a donut pattern; a patch, sector, Yagi, or parabolic antenna focuses energy. Gain is stated in dBi, and higher gain usually means a narrower beamwidth. MIMO APs use multiple radios and antennas; spatial streams raise throughput only with good SNR.
- PoE standards: 802.3af supplies 15.4 W at the PSE and about 12.95 W at the powered device; 802.3at supplies 30 W and 25.5 W; 802.3bt reaches 60 W or 90 W. Passive PoE is vendor-specific and not negotiated.
- Client software includes the wireless driver, supplicant, and OS configuration profile. Survey and spectrum-analysis tools are software, not AP features.
Worked example
An AP nameplate says 12 W. The switch port supports 802.3af. Reasoning: 802.3af provides 15.4 W at the switch and at least 12.95 W at the AP after cable loss, so 12 W fits. If the AP needed 20 W, or the link used a power-hungry 2.5 GbE module, 802.3at would be required.
Traps
Antenna gain does not create transmit power; it concentrates it. Cable and connector loss reduce the signal before the antenna. Do not confuse controller-based and autonomous management. Do not assume a higher-gain antenna improves coverage in every direction. A switch's total PoE budget, not only per-port wattage, can limit AP count.