CWNA Quality Control & Assurance 2 — Questions and Answers
Question 1: A wireless network administrator notices intermittent packet loss on a 5 GHz WLAN during business hours. Which QoS mechanism prioritizes voice traffic over bulk data to minimize the impact?
- WMM (Wi-Fi Multimedia) with DSCP markings (Correct answer)
- TKIP encryption with AES fallback
- 802.11r fast BSS transition
- Band steering to 2.4 GHz
Correct answer: WMM (Wi-Fi Multimedia) with DSCP markings
WMM combined with DSCP markings enables traffic prioritization so voice packets are queued ahead of bulk data, reducing perceived packet loss for real-time applications.
Question 2: During a post-deployment RF survey, an engineer finds that some areas show SNR values below 20 dB. What is the primary consequence of insufficient SNR in a WLAN?
- Increased authentication failures
- Higher MCS rates are unavailable, reducing throughput (Correct answer)
- IP address exhaustion in DHCP pools
- Increased 802.11 management frame overhead
Correct answer: Higher MCS rates are unavailable, reducing throughput
Low SNR forces clients to use lower MCS (Modulation and Coding Scheme) indices, which directly reduces maximum achievable throughput.
Question 3: Which metric is most useful when validating that a wireless deployment meets capacity requirements for a high-density venue?
- Channel utilization percentage per AP (Correct answer)
- BSSID count across the RF domain
- SSID broadcast interval
- Number of VLANs configured
Correct answer: Channel utilization percentage per AP
Channel utilization indicates how much of the available airtime is consumed; high utilization signals that clients will compete for medium access, degrading performance.
Question 4: An administrator uses a spectrum analyzer and observes a constant non-802.11 signal centered at 2.437 GHz. Which source is MOST likely causing this interference?
- A nearby 802.11ac AP on channel 6
- A Bluetooth device in frequency-hopping mode
- A 2.4 GHz video surveillance camera using a fixed channel (Correct answer)
- A 5 GHz cordless phone
Correct answer: A 2.4 GHz video surveillance camera using a fixed channel
Fixed-channel non-802.11 devices like analog video cameras produce a constant narrowband signal, while Bluetooth hops across the band and 802.11 devices would appear as 802.11 traffic.
Question 5: A CWNA candidate reviews a wireless site survey report showing –75 dBm RSSI at the cell edge. Why is RSSI alone insufficient to determine link quality?
- RSSI does not account for the noise floor, so SNR cannot be derived from it alone (Correct answer)
- RSSI is only valid for 2.4 GHz measurements
- RSSI values above –80 dBm always guarantee good throughput
- RSSI cannot be measured by passive survey tools
Correct answer: RSSI does not account for the noise floor, so SNR cannot be derived from it alone
RSSI reflects received signal strength but not the noise floor; without knowing the noise floor, you cannot calculate SNR, which is the true indicator of link quality.
Question 6: Which 802.11 frame type is used by clients to probe for available networks, and why does excessive probing degrade WLAN quality?
- Probe Request frames; they consume airtime and increase management frame overhead (Correct answer)
- Beacon frames; they flood the RF medium with AP advertisements
- Association Request frames; they trigger re-keying events
- RTS frames; they reserve the medium unnecessarily
Correct answer: Probe Request frames; they consume airtime and increase management frame overhead
Probe Requests are sent by clients scanning for SSIDs; high densities of legacy or roaming clients can generate significant management overhead that consumes shared airtime.
Question 7: When performing a pre-deployment predictive site survey, which input is MOST critical to producing accurate RF propagation models?
- Accurate floor plan with material attenuation values (Correct answer)
- The number of client devices expected per AP
- Planned IP addressing scheme
- SSID naming convention for each floor
Correct answer: Accurate floor plan with material attenuation values
Predictive tools use floor plan geometry and material attenuation values (e.g., concrete vs. drywall) to model signal propagation; inaccurate materials data leads to poor AP placement predictions.
CWNA Quality Control & Assurance 2
A wireless network administrator notices intermittent packet loss on a 5 GHz WLAN during business hours.
Which QoS mechanism prioritizes voice traffic over bulk data to minimize the impact?