CWNA-109 Exam Dumps : Certified Wireless Network Administrator

Cellular/LTE/5G is the best method for implementing a network backhaul for communications across the Internet in a remote area that is affected by a natural disaster. This is because cellular/LTE/5G networks are wireless and do not depend on physical infrastructure that may be damaged or unavailable in such scenarios. Cellular/LTE/5G networks also offer high-speed data transmission and wide coverage area, which are essential for emergency response operations. 802.11 bridging to the response team headquarters is not feasible because it requires line-of-sight and has limited range. Turning up the output power of the WLAN at the response team headquarters is not effective because it may cause interference and does not guarantee reliable connectivity. Temporary wired DSL is not practical because it requires installing cables and equipment that may not be available or accessible in a remote area. References: CWNA-109 Study Guide, Chapter 7: Wireless LAN Topologies, page 2031

The CWNA Official Study Guide (CWNA-109), Chapter 8: Troubleshooting and Spectrum Analysis, explains that hidden node problems occur when two or more client stations cannot hear each other but can both communicate with the same access point. This leads to collisions at the AP because the clients transmit simultaneously without sensing each other’s signals.

“Hidden node problems can often be identified in a protocol analyzer by observing excessive retransmissions from specific client stations. These retransmissions occur because the station’s frames are not acknowledged due to collisions caused by other stations that the transmitter cannot hear.”

— CWNA-108 Study Guide, Chapter 8, Hidden Node Problem Analysis, p. 393–395

Therefore, when analyzing for a hidden node issue, you will typically observe:

Retransmitted frames from multiple STAs.

Higher retry counts for affected stations compared to others.

Hence, the correct answer is C. Retransmitted frames from multiple STAs with higher retry counts than other STAs.

 iPerf is an open source tool that is designed to perform a throughput test on the WLAN. iPerf is a cross-platform command-line tool that can measure the bandwidth and quality of network links by generating TCP or UDP traffic between two endpoints. iPerf can run as either a server or a client mode, depending on whether it receives or sends traffic. iPerf can also report various metrics of network performance, such as throughput, jitter, packet loss, delay, and TCP window size. To perform a throughput test on the WLAN using iPerf, one device needs to run iPerf in server mode and another device needs to run iPerf in client mode. The devices need to be connected to the same WLAN network and have their IP addresses configured properly. The device running iPerf in client mode needs to specify the IP address of the device running iPerf in server mode as well as other parameters such as protocol, port number, duration, interval, bandwidth limit, packet size, etc. The device running iPerf in server mode will listen for incoming connections from the client device and send back acknowledgments or responses depending on the protocol used. The device running iPerf in client mode will send traffic to the server device according to the specified parameters and measure the network performance. The device running iPerf in client mode will display the results of the throughput test at the end of the test or at regular intervals during the test. The results can show the average, minimum, maximum, and instantaneous throughput of the network link, as well as other metrics such as jitter, packet loss, delay, and TCP window size. References: 1, Chapter 7, page 287; 2, Section 4.3