CWT Troubleshooting & Maintenance Procedures 5 — Questions and Answers
Question 1: A client's Wi-Fi connection drops every 60 minutes at exactly the same interval. What is the most likely cause?
- RF interference from DECT phones
- DHCP lease expiration and renewal failure (Correct answer)
- AP channel change due to DFS radar detection
- Client power-saving mode activating
Correct answer: DHCP lease expiration and renewal failure
Exactly timed disconnections at a fixed interval strongly suggest a DHCP lease expiration issue where the renewal is failing.
Question 2: When performing a post-change validation after an AP firmware upgrade, which test is most critical?
- Verify the AP's serial number label matches inventory
- Confirm clients can associate, authenticate, and pass traffic successfully (Correct answer)
- Check that the AP's LED color has changed
- Verify the AP's mounting hardware is still secure
Correct answer: Confirm clients can associate, authenticate, and pass traffic successfully
Post-change validation must confirm the full client lifecycle—association, authentication, and data traffic—to ensure the upgrade did not break WLAN functionality.
Question 3: A wireless network experiences a sudden increase in beacon frames observed on a spectrum analyzer. This most likely indicates:
- Clients are scanning for new networks aggressively
- A new AP or rouge device has come online broadcasting multiple SSIDs (Correct answer)
- The existing APs have increased their beacon interval
- A DFS event has forced a channel change
Correct answer: A new AP or rouge device has come online broadcasting multiple SSIDs
A surge in beacon frames typically means a new transmitter—possibly a rogue AP broadcasting multiple SSIDs—has appeared in the RF environment.
Question 4: During troubleshooting, you find an AP's 'retry rate' counter is above 20%. This metric indicates:
- High client throughput is being achieved
- Frame retransmissions are excessive, pointing to poor RF or interference (Correct answer)
- The AP is properly managing QoS queues
- Client roaming is functioning correctly
Correct answer: Frame retransmissions are excessive, pointing to poor RF or interference
A retry rate above 10-20% indicates the AP is frequently retransmitting frames because clients are not acknowledging them, which degrades throughput.
Question 5: A newly deployed outdoor AP operating on a DFS channel goes offline every afternoon. The most likely explanation is:
- Thermal shutdown due to direct sunlight exposure
- Radar pulses from nearby aviation or weather radar triggering a DFS event (Correct answer)
- The AP's PoE budget is reduced during peak usage
- Afternoon lightning storms resetting the CAPWAP tunnel
Correct answer: Radar pulses from nearby aviation or weather radar triggering a DFS event
DFS channels require APs to vacate the channel upon radar detection, and recurring afternoon events align with radar patterns such as airport approach or weather radar scanning.
Question 6: What is the correct procedure when an AP's configuration becomes corrupted and it boots into a recovery mode?
- Replace the AP immediately as it is unrecoverable
- Use the console port or recovery TFTP server to reload a valid firmware or configuration image (Correct answer)
- Power cycle the AP 10 times to trigger a factory reset
- Remove the AP from the controller and re-add it via the GUI
Correct answer: Use the console port or recovery TFTP server to reload a valid firmware or configuration image
Most enterprise APs support recovery via console port or TFTP boot, allowing a technician to restore firmware or configuration without hardware replacement.
Question 7: A technician is tasked with establishing a baseline for future WLAN troubleshooting. Which set of metrics should be documented?
- Client hardware serial numbers and purchase dates
- Channel utilization, noise floor, RSSI per AP, client counts, and throughput under normal load (Correct answer)
- SSID broadcast intervals and WPA handshake timers
- AP firmware versions and physical mounting heights only
Correct answer: Channel utilization, noise floor, RSSI per AP, client counts, and throughput under normal load
A useful WLAN baseline includes RF metrics (noise floor, RSSI, channel utilization) and performance metrics (client count, throughput) captured during normal operation for comparison during incidents.
CWT Troubleshooting & Maintenance Procedures 5
A client's Wi-Fi connection drops every 60 minutes at exactly the same interval.
What is the most likely cause?