Which one of the following should be the first step when troubleshooting a WLAN issue?
- A . Identify capture locations
- B . Identify probable causes
- C . Perform an initial WLAN scan and see if any obvious issues stand out
- D . Define the problem
Which one of the best following is an advantage of using display filters instead of capture-time filters?
- A . Display filters allow for focused analysis on just the packets of interest
- B . Once created display filters are reusable for later captures
- C . Display filters only hide the packets from view and the filtered packets can be enabled for view later
- D . Multiple display filters can be applied simultaneously
A
Explanation:
display filters allow you to focus on things of interest and to ignore things you don’t care about.
Reference: https://searchnetworking.techtarget.com/tip/How-to-manage-Wireshark-display-filters
Using a portable analyzer you perform a packet capture next to a client STA and you can see that the STA is associated to a BSS. You observe the STA sending packets to the AP and the AP sending packets to the STA. Less the 2% of all packets are retransmissions. You move to capture packets by the AP and, while the retry rate is still very low, you now only see unidirectional traffic from the AP to the client.
How do you explain this behavior?
- A . There is a transmit power mismatch between the client and the AP and while the client can hear the Aps traffic, the AP cannot hear the client.
- B . The portable analyzer has a lower receive sensitivity than the AP and while it can’t capture the packets
from the client STA, the AP can receive them OK. - C . The STA is transmitting data using more spatial streams than the potable analyzer can support
- D . The portable analyzer is too close to the AP causing CCI, blinding the AP to the client’s packets
Given a protocol analyzer can decrypt WPA2-PSK data packets providing the PSK and SSID are configured in the analyzer software.
When performing packet capture (in a non-FT environment) which frames are required in order for PSK frame decryption to be possible?
- A . Authentication
- B . Reassociation
- C . 4-Way Handshake
- D . Probe Response
When configuring a long term, forensic packet capture and saving all packets to disk which of the following is not a consideration?
- A . Total capture storage space
- B . Individual trace file size
- C . Real-time packet decodes
- D . Analyzer location
You are performing a multiple adapter channel aggregation capture to troubleshoot a VoIP roaming problem and would like to measure the roaming time from the last VoIP packet sent on the old AP’s channel to the first VoIP packet sent on the new AP’s channel.
Which timing column in the packet view would measure this for you?
- A . Delta
- B . Absolute
- C . Roaming
- D . Relative
Protocol analyzers may present field values in either binary, decimal or hexadecimal.
What precedes a
hexadecimal value to indicate it is hexadecimal?
- A . 0x
- B . %
- C . HEX
- D . 16x
Which one of the these is the most important in the WLAN troubleshooting methodology among those listed?
- A . Interview the network manager about the issues being experienced
- B . Talk to the end users about their experiences
- C . Observe the problem
- D . Obtain detailed knowledge of the wireless vendors debug and logging options
The network administrator at ABC Engineering has taken a large packet capture from one of their APs running in monitor mode. She has very little knowledge of 802.11 protocols but would like to use the capture file to evaluate the overall health and performance of their wireless network. When she asks your advice, which tool do you recommend she opens the packet capture file with?
- A . Capture visualization tool
- B . Protocol analyzer
- C . Spectrum analyzer
- D . WLAN scanner
802.11k Neighbor Requests and Neighbor Reports are sent in what type of Management Frames?
- A . RRM
- B . Action
- C . Beacon
- D . Reassociation Request and Reassociation Response
Which one of the following is required for Wi-Fi integration in laptop-based Spectrum Analyzer software?
- A . A supported WLAN adaptor with a customized driver
- B . Any 802.11 wireless adaptor
- C . A dual radio spectrum analyzer card
- D . SNMP read credentials to the WLAN controller or APs
You’re the WLAN administrator for a large retailer based at the HQ in New York. The London-based office has been complaining about WLAN disconnections around lunch time each day. You suspect this might be interference from the staff microwave, how might you test your theory from the New York office?
- A . Access the microwave remotely and run a diagnostic check
- B . Ask a local member of staff to take some pictures of the microwave, including some close-ups of the door seal so that you can access it
- C . Place one of the London APs into spectrum analyzer mode and monitor the situation over lunch time
- D . Ask a local member of staff to change the frequency of the microwave and see if the disconnections stop
ABC International has installed a new smart ZigBee controlled lighting system.
However, the network team is concerned that this new system will interface with the existing WLAN and has asked you to investigate the impact of the two systems operating simultaneously in the 2.4 GHz band. When performing Spectrum Analysis, which question could you answer by looking at the FFT plot?
- A . Do the ZigBee channels used by the lightning system overlap with the WLAN channels?
- B . Is the ZigBee system using more the 50% of the available airtime?
- C . Is the ZigBee system causing an increase in WLAN retries?
- D . Is the WLAN corrupting ZigBee system messages?
In a Spectrum Analyzer the Swept Spectrogram plot displays what information?
- A . The RF time domain
- B . RF power present at a particular frequency over the course of time
- C . Wi-Fi Device information
- D . Duty cycle in the frequency domain
You have installed a new 802.11ac WLAN configured with 80 MHz channels. Users in one area are
complaining about poor performance. This area is currently served by a single AP. You take a spectrum
analysis capture in the poor performing areA. While examining the waterfall plot you notice the airtime
utilization is higher on the first 20 MHz of the 80 MHz channel when compared to the rest of the channel.
What do you conclude?
- A . The AP is misconfigured and needs to be reconfigured to 80MHz operation
- B . RRM is enabled and has dynamically picked a 20 MHz channel
- C . The first 20 MHz is the AP’s primary channel and higher airtime utilization on the primary channel is normal when an AP Is configured for 80 MHz operation
- D . Non Wi-Fi interference is preventing the APs 80 MHz operation
Which common feature of a Spectrum Analyzer would be the best to help you locate a non-802.11
interference source?
- A . Max hold
- B . Location filter
- C . Waterfall plot
- D . Device finder
A manufacturing facility has installed a new automation system which incorporates an 802.11 wireless network. The automation system is controlled from tablet computers connected via the WLAN.
However, the automation system has not gone live due to problem with the tablets connecting to the WLAN. The WLAN vendor has been onsite to perform a survey and confirmed good primary and secondary coverage across the facility. As a CWAP you are called in to perform Spectrum Analysis to identify any interference sources. From the spectrum analysis, you did not identify any interference sources but were able to correctly identify the issue.
Which of the following issues did you identify from the spectrum analysis?
- A . The tablets are entering power save mode and failing to wake up to receive the access points
transmissions - B . A high noise floor has resulted in a SNR of less than 20%
- C . The tablets are connecting to the wrong SSID
- D . There is a power mismatch between the APs and the clients
Finish the statement. It is possible to distinguish between _______and ______20 MHz transmissions when looking at an FFT plot.
- A . HR/DSSS and ERP
- B . ERP and VHT
- C . HT and VHT
- D . OFDM and HT
What is the function of the PMD sub-layer?
- A . Converts 1s and 0s given to it by the PLCP sub-layer into the appropriate RF signals
- B . Provides framing
- C . Adds a PHY preamble and header to a PSDU
- D . Performs A-MPDU
What is the function of the PHY Preamble?
- A . To set the modulation method for the MPDU
- B . Allows the receiver to detect and synchronize with the signal
- C . To terminate a conversation between transmitter and receiver
- D . Carries the NDP used in Transmit Beamforming and MU-MIMO