CWS CWS WLAN Troubleshooting 2 — Questions and Answers
Question 1: Which tool captures 802.11 frames for detailed protocol-level analysis?
- Spectrum analyzer
- Wireless protocol analyzer (packet sniffer) (Correct answer)
- Wi-Fi scanner mobile app
- SNMP management console
Correct answer: Wireless protocol analyzer (packet sniffer)
A wireless protocol analyzer captures 802.11 frames at the MAC layer for detailed analysis of association, authentication, and data exchange sequences.
Question 2: A wireless client can associate with the AP but cannot reach any internet resources. Pinging the default gateway succeeds. What is the most likely cause?
- WLAN security configuration mismatch
- DNS resolution failure (Correct answer)
- RF channel interference at the AP
- AP transmit power set too low
Correct answer: DNS resolution failure
If the default gateway is reachable but internet resources are not, DNS failure is most likely since domain names cannot be resolved to IP addresses.
Question 3: What does RSSI measure in a wireless network?
- The ambient noise floor at the AP location
- The relative power level of the received RF signal at the receiver (Correct answer)
- The data throughput of the current wireless link
- The number of frame retransmissions per second
Correct answer: The relative power level of the received RF signal at the receiver
RSSI (Received Signal Strength Indicator) is a measurement of the power level of the received RF signal, typically expressed as a negative value in dBm.
Question 4: When multiple APs in the same area are configured to use the same 802.11 channel, what problem results?
- Adjacent channel interference (ACI)
- Co-channel interference (CCI) and increased contention (Correct answer)
- Hidden node collisions between APs
- Near/far power imbalance
Correct answer: Co-channel interference (CCI) and increased contention
Co-channel interference (CCI) forces all devices sharing the same channel to contend for the medium, reducing throughput and increasing latency.
Question 5: A wireless user reports slow speeds only in a specific conference room while other areas work fine. What is the most likely cause?
- AP firmware bug affecting all clients
- Insufficient DHCP address pool
- RF interference or poor signal coverage in that area (Correct answer)
- VLAN misconfiguration on the switch
Correct answer: RF interference or poor signal coverage in that area
Location-specific performance issues typically point to RF factors such as signal attenuation, multipath, or localized interference in that particular area.
Question 6: Which of the following is a Layer 2 WLAN troubleshooting issue?
- IP address conflict between two clients
- Failed DNS query to external server
- Authentication or association failure with the AP (Correct answer)
- Default gateway unreachable from client
Correct answer: Authentication or association failure with the AP
Authentication and association are Layer 2 (MAC layer) processes; failures at this stage prevent the client from completing the wireless connection.
Question 7: What is the purpose of conducting a post-deployment site survey for WLAN troubleshooting?
- To configure SSID passwords on all APs
- To verify that actual signal coverage and channel usage match the design (Correct answer)
- To update AP firmware to the latest version
- To assign static IP addresses to all APs
Correct answer: To verify that actual signal coverage and channel usage match the design
A post-deployment site survey validates that the installed WLAN delivers the expected coverage, channel plan, and signal quality as designed.
CWS CWS WLAN Troubleshooting 2
Which tool captures 802.11 frames for detailed protocol-level analysis?