CWNA Wireless Network Administrator MCQ 4 — Questions and Answers
Question 1: Which 802.11 power-save mechanism allows the AP to buffer frames and notify sleeping clients via the Traffic Indication Map (TIM)?
- WMM-PS (U-APSD)
- Legacy Power Save Mode (PSM) (Correct answer)
- APSD Scheduled mode
- Target Wake Time (TWT)
Correct answer: Legacy Power Save Mode (PSM)
Legacy PSM has clients sleep between beacon intervals; the AP buffers their frames and sets bits in the TIM element of beacons to wake the relevant clients.
Question 2: A wireless engineer is performing a passive site survey. What is the primary activity during this phase?
- Transmitting test traffic to measure throughput
- Walking the area and capturing RF signals without connecting to an AP (Correct answer)
- Installing access points in planned locations
- Configuring WPA2-Enterprise on all APs
Correct answer: Walking the area and capturing RF signals without connecting to an AP
A passive survey involves listening to the RF environment with a scanning adapter, capturing signal levels and interference without associating to any network.
Question 3: What distinguishes a controller-based WLAN architecture from an autonomous AP deployment?
- Controller-based APs use a different frequency band
- Centralized management and data forwarding through a WLAN controller (Correct answer)
- Autonomous APs cannot support WPA2 encryption
- Controller-based WLANs require proprietary client drivers
Correct answer: Centralized management and data forwarding through a WLAN controller
In controller-based architectures, lightweight APs tunnel traffic (often via CAPWAP) to a central controller that handles management, policy, and often data forwarding.
Question 4: What is the role of CAPWAP in a split-MAC WLAN architecture?
- Provides client IP addressing via DHCP relay
- Tunnels control and data traffic between lightweight APs and the WLC (Correct answer)
- Encrypts 802.11 frames end-to-end between client and server
- Manages 802.1X supplicant credentials
Correct answer: Tunnels control and data traffic between lightweight APs and the WLC
CAPWAP (Control And Provisioning of Wireless Access Points) is the standard protocol that encapsulates and tunnels both control-plane and data-plane traffic between a lightweight AP and its controller.
Question 5: Which metric describes the ratio of correctly received bits to total transmitted bits and is used to measure wireless link quality?
- RSSI
- SNR
- Bit Error Rate (BER) (Correct answer)
- MCS Index
Correct answer: Bit Error Rate (BER)
BER measures the proportion of bit errors in a transmission and is a direct indicator of link quality; a higher BER typically corresponds to a weaker or noisier signal.
Question 6: A 5 GHz channel is configured for 80 MHz width under 802.11ac. How many 20 MHz sub-channels make up this channel?
- 2
- 4 (Correct answer)
- 8
- 6
Correct answer: 4
An 80 MHz channel consists of four bonded 20 MHz sub-channels, which is a key feature of 802.11ac Wave 1.
Question 7: Which statement correctly describes the difference between 2.4 GHz and 5 GHz bands for indoor WLAN deployments?
- 5 GHz provides greater range but fewer non-overlapping channels
- 2.4 GHz offers more non-overlapping channels and higher throughput
- 5 GHz supports more non-overlapping channels and higher potential throughput, but has shorter range (Correct answer)
- 2.4 GHz is immune to interference from microwave ovens
Correct answer: 5 GHz supports more non-overlapping channels and higher potential throughput, but has shorter range
The 5 GHz band offers 24+ non-overlapping 20 MHz channels (in the US) and less congestion, enabling higher throughput, but its higher frequency means greater path loss and shorter effective range.
CWNA Wireless Network Administrator MCQ 4
Which 802.11 power-save mechanism allows the AP to buffer frames and notify sleeping clients via the Traffic Indication Map (TIM)?