CWNA-108 Practice Exam Questions with Answers Certified Wireless Network Administrator Certification

The common spectrum analyzer view that you should use for this analysis is the Waterfall/Spectrogram view. The Waterfall/Spectrogram view shows the signal from the interfering device over time on a three-dimensional graph. The x-axis represents frequency, the y-axis represents time, and the z-axis represents amplitude or power. The color of each pixel indicates the signal strength at a given frequency and time. The Waterfall/Spectrogram view can help you identify the characteristics of the interference source, such as its frequency range, duty cycle, modulation type, and pattern. References: [CWNP Certified Wireless Network Administrator Official Study Guide: Exam CWNA-107], page 524; [CWNA: Certified Wireless Network Administrator Official Study Guide: Exam CWNA-106], page 494.

What is always required to establish a high quality 2.4 GHz RF link at a distance of 3 miles (5 kilometers) is a Fresnel Zone that is at least 60% clear of obstructions. The Fresnel Zone is an elliptical-shaped area around the line-of-sight path between two antennas that reflects and refracts the RF waves. The Fresnel Zone radius depends on the frequency of the RF signal and the distance between the antennas. For optimal performance, the Fresnel Zone should be at least 60% clear of any obstructions that may cause interference, attenuation, or multipath fading. The minimum output power level, antenna gain, and antenna type may vary depending on the environmental conditions and regulatory constraints, but they are not always required for a high quality RF link. References: [CWNP Certified Wireless Network Administrator Official Study Guide: Exam CWNA-107], page 75; [CWNA: Certified Wireless Network Administrator Official Study Guide: Exam CWNA-106], page 65.

In an 802.11 2.4 GHz system, channels 1 and 5 are considered non-overlapping. In the 2.4 GHz band, there are 14 channels defined by the IEEE 802.11 standard, but only 11 of them are available in North America and most other regions. Each channel has a bandwidth of 22 MHz, but they are spaced only 5 MHz apart from each other. This means that adjacent channels overlap with each other and cause interference. To avoid interference, it is recommended to use only non-overlapping channels, which are channels that do not share any frequency range with each other. In the 2.4 GHz band, there are only three non-overlapping channels: channel 1, channel 6, and channel 11. However, some devices can use channel bonding to combine two adjacent channels into one wider channel of 40 MHz, which can provide higher throughput but also more interference. In this case, there are only two non-overlapping channels: channel 1+5 and channel 6+10. References: 1, Chapter 3, page 86; 2, Section 3.2

 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

DHCP (Dynamic Host Configuration Protocol) is the network service where option 43 must be configured to allow access points to locate controllers. DHCP is a protocol that allows a device to obtain an IP address and other network configuration parameters from a server. In a wireless controller scenario, the access points can use DHCP to request an IP address from a DHCP server, which can also provide the IP address or hostname of the wireless controller as an option in the DHCP response. Option 43 is a vendor-specific option that can be used to encode custom information for different types of devices. For example, Cisco access points can use option 43 to receive the IP address of the wireless controller from the DHCP server, while Aruba access points can use option 43 to receive the hostname of the wireless controller from the DHCP server. This way, the access points can discover the wireless controller and establish a connection with it. References: 1, Chapter 8, page 309; 2, Section 5.2

Granting access to specific network services or resources according to a user profile describes the authorization component of a AAA implementation. AAA stands for Authentication, Authorization, and Accounting, which are three functions that are used to control and monitor access to network resources and services. Authentication is the process of verifying that a user is who he says he is, by using credentials such as username, password, certificate, token, or biometric data. Authorization is the process of granting access to specific network services or resources according to a user profile, which defines the user’s role, privileges, and permissions. Accounting is the process of recording and reporting the usage of network services or resources by a user, such as the duration, volume, type, and location of the access. AAA can be implemented by using different protocols and servers, such as RADIUS, TACACS+, LDAP, Kerberos, or Active Directory. References: 1, Chapter 11, page 449; 2, Section 7.1

A laptop-based spectrum analyzer with a directional antenna is the best solution for locating a non-802.11 device that is suspected of causing interference on the WLAN. A spectrum analyzer is a device or a software application that can measure and display the frequency spectrum of electromagnetic signals in a given range. A spectrum analyzer can show the amplitude, frequency, bandwidth, modulation, and other characteristics of different signals in the spectrum, which can help identify their sources and types. A spectrum analyzer can also detect non-802.11 devices that may cause interference on the WLAN, such as microwave ovens, cordless phones, Bluetooth devices, or radar systems. A laptop-based spectrum analyzer is a software application that runs on a laptop computer and uses an external USB adapter as its RF interface. A laptop-based spectrum analyzer has the advantage of being portable, flexible, and cost-effective compared to a hardware-based spectrum analyzer. A directional antenna is an antenna that radiates or receives RF signals more strongly in one direction than in others. A directional antenna has a high gain and a narrow beamwidth, which means it can focus the RF energy in a specific direction and reduce the interference from other directions. A directional antenna can also increase the range and sensitivity of the RF signal detection. To locate a non-802.11 device that is causing interference on the WLAN, a laptop-based spectrum analyzer with a directional antenna can be used to perform a technique called RF hunting or triangulation. This technique involves pointing the directional antenna in different directions and observing the signal strength and characteristics of the interfering device on the spectrum analyzer. By moving around and changing the direction of the antenna, the location of the interfering device can be estimated based on where the signal strength is highest and most consistent. References: 1, Chapter 7, page 282; 2, Section 4.3

An IEEE 802.11 amendment is a proposed change or addition to the existing 802.11 standard, which defines the specifications and protocols for wireless LANs. An amendment goes through several stages of development, such as draft, sponsor ballot, and final approval, before it is ratified by the IEEE Standards Association and becomes part of the standard. Until then, it has no official impact on the standard, although some vendors may release products based on draft amendments to gain a competitive edge or to influence the final outcome of the amendment . References: [CWNA-109 Study Guide], Chapter 1: Overview of Wireless Standards, Organizations, and Fundamentals, page 25; [CWNA-108 Study Guide], Chapter 1: Overview of Wireless Standards, Organizations, and Fundamentals, page 23; [IEEE website], IEEE-SA Standards Development Process.

 The data rate of a signal is the speed that the data bits in individual 802.11 data frames are sent, but it does not account for the actual amount of data that can be transmitted over time. The throughput of a connection is the flow of information over time, which is affected by various factors such as data encoding, modulation, encryption, airtime utilization, noise levels, interference, etc. Therefore, the throughput is always lower than the data rate. According to one of the web search results1, the actual throughput is normally 60-70 percent of the supported data rates. So, for a connection with a data rate of 150 Mbps, the expected throughput would be around 90-105 Mbps.

An IBSS is used instead of a BSS is a network configuration that would result in multiple stations broadcasting Beacon frames with the same BSSID but with different source addresses. An IBSS (Independent Basic Service Set) is a type of WLAN that does not use an AP but rather allows stations to communicate directly with each other in a peer-to-peer manner. An IBSS is also known as an ad-hoc network or a peer-to-peer network. In an IBSS, each station generates its own Beacon frames to announce its presence and capabilities to other stations within range. The Beacon frames have the same BSSID, which is randomly generated by one of the stations when creating the IBSS, but they have different source addresses, which are the MAC addresses of each station’s radio interface. The BSSID is used to identify the IBSS and prevent stations from joining other IBSSs with different BSSIDs. References: , Chapter 1, page 25; , Section 1.1

When performing a post-deployment validation survey for voice over Wi-Fi (VoWiFi), an action that must be performed is Application analysis with an active phone call on a VoWiFi handset. Application analysis is a method of testing the performance of a specific application over the WLAN by measuring parameters such as throughput, latency, jitter, packet loss, MOS score, and R-value. Application analysis with an active phone call on a VoWiFi handset can help to evaluate the quality of service (QoS) and user experience of VoWiFi calls over the WLAN. It can also help to identify any issues or bottlenecks that may affect VoWiFi calls such as interference, roaming delays, or insufficient coverage. References: [CWNP Certified Wireless Network Administrator Official Study Guide: Exam CWNA-107], page 549; [CWNA: Certified Wireless Network Administrator Official Study Guide: Exam CWNA-106], page 519.

 This is because the passphrase for WPA2-Personal is case-sensitive and must match exactly on both the AP and the client. If the passphrase is entered incorrectly on the client, the client will not be able to authenticate with the AP and connect to the network. The AP that covers the problem area is not likely to require a firmware update, fail, or be improperly configured, as it is online and works with other clients that have the correct passphrase. To troubleshoot this issue, you can check the passphrase settings on the clients and make sure they match with the AP. You can also try to reconnect the clients to the network or reboot them if necessary. For more information on how to configure WPA2-Personal on your router

The beamwidth of an RF antenna is the angular measure of how wide the main lobe of radiation is. The main lobe is the area where the signal strength is highest and most concentrated. The beamwidth is calculated at the points where the main lobe decreases power by 3 dB, which means it is half of the maximum power. The beamwidth can be measured in both horizontal and vertical planes, depending on how the antenna is oriented. The horizontal beamwidth is also called azimuth, while the vertical beamwidth is also called elevation. The beamwidth patterns on an antenna polar chart indicate how the RF energy is distributed in different directions. References: 1, Chapter 2, page 66; 2, Section 2.3

WPA2 is the acronym for Wi-Fi Protected Access 2, which is a security standard for wireless networks that was introduced in 2004 as an improvement over the original WPA standard. WPA2 is based on the IEEE 802.11i amendment, which specifies the use of CCMP/AES (Counter Mode with Cipher Block Chaining Message Authentication Code Protocol/Advanced Encryption Standard) as the mandatory encryption and authentication method for WLANs. WPA2 also supports optional methods such as TKIP (Temporal Key Integrity Protocol), which is backward compatible with WEP (Wired Equivalent Privacy), and EAP (Extensible Authentication Protocol), which allows for various types of authentication mechanisms . References: [CWNA-109 Study Guide], Chapter 10: Wireless LAN Security, page 403; [CWNA-108 Study Guide], Chapter 10: Wireless LAN Security, page 393; [CWNP website], CWSP Certification.

Channel 144 is a new channel that was added to the 5 GHz band by the 802.11ac amendment, which defines the VHT (Very High Throughput) PHY for WLANs. Channel 144 has a center frequency of 5720 MHz and a bandwidth of 20 MHz. It can also be combined with adjacent channels to form wider channels of 40 MHz, 80 MHz, or 160 MHz. Channel 144 is available in some regions, such as North America and Europe, but not in others, such as Japan and China . References: [CWNA-109 Study Guide], Chapter 3: Antennas and Accessories, page 121; [CWNA-108 Study Guide], Chapter 3: Antennas and Accessories, page 115; [Wikipedia], List of WLAN channels.

A probe request frame is a management frame that is sent by a client station to discover available wireless networks in its vicinity. A probe request can be either unicast or broadcast, depending on whether it specifies a particular SSID (Service Set Identifier) or a wildcard SSID. A broadcast probe request with a wildcard SSID is used to solicit responses from all APs within range, regardless of their SSIDs. Each AP that receives a broadcast probe request prepares a probe response frame that contains information about its network, such as SSID, supported rates, channel, security, etc. However, before sending the probe response, each AP must contend for the medium using the CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) protocol, which is the basic access method for 802.11 WLANs. This means that each AP must sense the channel for a DIFS (Distributed Interframe Space) interval, which is longer than a SIFS interval, and then generate a random backoff time before transmitting. This reduces the probability of collisions and ensures fair access to the medium among multiple APs. Therefore, each AP responds in turn after preparing a probe response and winning contention . References: [CWNA-109 Study Guide], Chapter 5: IEEE 802.11 Medium Access, page 215; [CWNA-108 Study Guide], Chapter 5: IEEE 802.11 Medium Access, page 209; [CWNA-109 Study Guide], Chapter 6: Wireless LAN Devices and Topologies, page 255.

The clients are 802.11n devices. 802.11n devices can only support a maximum of four spatial streams, and the maximum data rate for a single spatial stream is 150 Mbps. Therefore, if most clients are only achieving 150 Mbps, it means they are using only one spatial stream, which is typical for 802.11n devices. To achieve higher data rates, the clients would need to support more spatial streams, which is possible with 802.11ax devices12.

The other options are not correct because they do not explain why most clients are only achieving 150 Mbps. Option B is incorrect because two stream 802.11ax clients can achieve data rates of up to 574 Mbps in a 20 MHz channel1. Option C is incorrect because contention caused by an overlapping BSS would affect all clients, not just most of them, and it would also reduce the throughput, not the data rate. Option D is incorrect because non-Wi-Fi interference in the channel would also affect all clients, not just most of them, and it would also cause errors and retransmissions, not lower data rates.

References: 1: CWNA-108 Official Study Guide, page 144 2: 802.11ax data rates

A common problem that causes this scenario is captive portal issues. A captive portal is a web page that requires users to authenticate or accept terms and conditions before accessing the Internet through a WLAN. A captive portal is often used for guest networks to provide security and control over the network access. A captive portal works by intercepting the user’s web requests and redirecting them to the portal page until the user completes the required action. However, sometimes the captive portal may not work properly due to various reasons, such as browser settings, firewall rules, DNS configuration, or network errors. This can prevent the user from browsing the Internet or seeing the portal page. To troubleshoot captive portal issues, you can try to use a different browser, clear the browser cache and cookies, disable any VPN or proxy settings, manually enter the portal URL, or contact the network administrator. NTP issues, hardware issues, or IP routing issues are not common problems that cause this scenario. References: [CWNP Certified Wireless Network Administrator Official Study Guide: Exam CWNA-107], page 343; [CWNA: Certified Wireless Network Administrator Official Study Guide: Exam CWNA-106], page 333.

The short guard interval is an optional feature of 802.11n and 802.11ac that reduces the time between OFDM symbols from 800 ns to 400 ns. This can increase the data rate by about 11%, but also requires more precise timing and synchronization between the transmitter and the receiver. The short guard interval is only used when both the AP and the client support it and agree to use it . References: [CWNA-109 Study Guide], Chapter 4: Radio Frequency Signal and Antenna Concepts, page 163; [CWNA-108 Study Guide], Chapter 4: Radio Frequency Signal and Antenna Concepts, page 157.

 What you should tell him is that due to 802.11 network operations and the dynamic rates used by devices on the network, the two radios will likely not exceed the 1 Gbps Ethernet link. This is because the actual throughput of an 802.11 network is much lower than the theoretical data rates due to factors such as overhead, contention, interference, retransmissions, and environmental conditions. Moreover, the data rates used by devices on the network vary depending on their distance, signal quality, capabilities, and configuration. Therefore, it is unlikely that both radios of the AP will simultaneously use the maximum data rates and saturate the 1 Gbps Ethernet link. Upgrading to a 10 Gbps Ethernet link or running a second 1 Gbps Ethernet link may be unnecessary and costly. Compressing all data before transmitting it onto the Ethernet link may introduce additional overhead and latency. References: [CWNP Certified Wireless Network Administrator Official Study Guide: Exam CWNA-107], page 227; [CWNA: Certified Wireless Network Administrator Official Study Guide: Exam CWNA-106], page 217.

https://www.cablinginstall.com/articles/2012/08/cat-6a-vs-cat-5e-poe.html

The statement that the lowest voltage drop is achieved when using CAT6 cable instead of Cat5 or CAT5e is true about 802.3, Clause 33 Power over Ethernet. Power over Ethernet (PoE) is a technology that allows electrical power to be delivered over Ethernet cables along with data signals. PoE is defined by IEEE 802.3, Clause 33 and has several variants, such as PoE (802.3af), PoE+ (802.3at), and PoE++ (802.3bt). PoE works by using a device called PSE (Power Sourcing Equipment) that injects power into the Ethernet cable and a device called PD (Powered Device) that receives power from the Ethernet cable. The PSE can be either an endpoint device, such as a switch or a router, or a midspan device, such as an injector or a splitter, that is inserted between two Ethernet devices. The PD can be any device that requires power, such as an access point, a camera, or a phone.

One of the factors that affects PoE performance is voltage drop, which is the reduction of voltage that occurs as current flows through a cable due to its resistance. Voltage drop can cause power loss and inefficiency in PoE systems, as well as damage to PDs if the voltage falls below their minimum requirement. To minimize voltage drop, it is recommended to use high-quality cables with low resistance and short length. Among the common types of Ethernet cables, CAT6 has the lowest resistance and therefore the lowest voltage drop compared to Cat5 or CAT5e. CAT6 also has higher bandwidth and data rate than Cat5 or CAT5e, making it more suitable for PoE applications. References: 1, Chapter 7, page 263; 2, Section 4.4

SAE (Simultaneous Authentication of Equals) is required when operating 802.11ax APs in the 6 GHz band using passphrase-based authentication. SAE is a secure and robust authentication method that is defined in the IEEE 802.11s amendment and is also known as WPA3-Personal or WPA3-SAE. SAE is based on a cryptographic technique called Dragonfly Key Exchange, which allows two parties to establish a shared secret key using a passphrase, without revealing the passphrase or the key to an eavesdropper or an attacker. SAE also provides forward secrecy, which means that if the passphrase or the key is compromised in the future, it does not affect the security of past communications.

SAE is required when operating 802.11ax APs in the 6 GHz band using passphrase-based authentication because of the new regulations and standards that apply to this band. The 6 GHz band is a new frequency band that was opened for unlicensed use by the FCC and other regulatory bodies in 2020. The 6 GHz band offers more spectrum and less interference than the existing 2.4 GHz and 5 GHz bands, which can enable higher performance and efficiency for Wi-Fi devices. However, the 6 GHz band also has some restrictions and requirements that are different from the other bands, such as:

• The 6 GHz band is divided into two sub-bands: U-NII-5 (5925-6425 MHz) and U-NII-7 (6525-6875 MHz). The U-NII-5 sub-band is subject to DFS (Dynamic Frequency Selection) rules, which require Wi-Fi devices to monitor and avoid using channels that are occupied by radar systems or other primary users. The U-NII-7 sub-band is not subject to DFS rules, but it has a lower maximum transmit power limit than the U-NII-5 sub-band.
• The Wi-Fi devices that operate in the 6 GHz band are called 6E devices, which stands for Extended Spectrum. 6E devices must support 802.11ax technology, which is also known as Wi-Fi 6 or High Efficiency (HE). 802.11ax is a new standard that improves the performance and efficiency of Wi-Fi networks by using features such as OFDMA (Orthogonal Frequency Division Multiple Access), MU-MIMO (Multi-User Multiple Input Multiple Output), BSS Coloring, TWT (Target Wake Time), and HE PHY and MAC enhancements.
• The 6E devices that operate in the 6 GHz band must also support WPA3 security, which is a new security protocol that replaces WPA2 and provides stronger encryption and authentication for Wi-Fi networks. WPA3 has two modes: WPA3-Personal and WPA3-Enterprise. WPA3-Personal uses SAE as its authentication method, which requires a passphrase to establish a secure connection between two devices. WPA3-Enterprise uses EAP (Extensible Authentication Protocol) as its authentication method, which requires a certificate or a credential to authenticate with a server.

Therefore, SAE is required when operating 802.11ax APs in the 6 GHz band using passphrase-based authentication because it is part of WPA3-Personal security, which is mandatory for 6E devices in this band. References: , Chapter 3, page 120; , Section 3.2

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a mesh portal is a device that connects a mesh BSS (MBSS) to an Ethernet network, such as the Internet. A mesh portal acts as a bridge between the wired and wireless domains, and allows the mesh stations to communicate with external networks. A mesh portal is also a mesh point, which means it can forward traffic within the MBSS.

The other options are not correct. Option A. Mesh Gate is a device that connects a mesh BSS (MBSS) to another mesh BSS or another wireless network, such as an infrastructure BSS or an ad hoc network2. A mesh gate acts as a gateway between different wireless domains, and allows the mesh stations to communicate with other wireless networks. A mesh gate is also a mesh point, which means it can forward traffic within the MBSS. Option B. Mesh Switch is not a valid term in the 802.11 standard. Option C. Mesh Router is also not a valid term in the 802.11 standard.

The statement that in modern networks, both centralized and distributed data forwarding work well for most standard office deployments is true about WLAN performance. Data forwarding refers to how wireless frames are transmitted from wireless clients to wired networks or vice versa through wireless access points (APs). Centralized data forwarding means that all wireless frames are sent to a central controller or gateway before being forwarded to their destinations. Distributed data forwarding means that wireless frames are forwarded directly by the APs to their destinations without going through a central controller or gateway. Both methods have their advantages and disadvantages, depending on the network size, topology, traffic pattern, security, and management requirements. However, in modern networks, both methods can achieve high performance and scalability for most standard office deployments, as they can leverage advanced features such as fast roaming, load balancing, quality of service, and encryption. The other statements about WLAN performance are false. In most WLANs, special skill or tuning is required to get peak performance, such as selecting the appropriate channel, power, data rate, and antenna settings. WLANs perform worse as more wireless clients connect with each AP, as they cause more contention and interference on the wireless medium. To get the best performance out of an AP, you should not disable data rates of 72 Mbps and lower, as they are needed for backward compatibility and range extension. References: CWNA-109 Study Guide, Chapter 9: Wireless LAN Architecture, page 2811

To calculate the EIRP at the antenna element, we need to add the transmitter output power, subtract the cable loss, and add the antenna gain. All these values need to be converted to dBm first, if they are not already given in that unit. In this case, we have:

Transmitter output power = 50 mW = 10 log (50) dBm = 16.99 dBm Cable loss = 3 dB Antenna gain = 9 dBi

EIRP = Transmitter output power - Cable loss + Antenna gain EIRP = 16.99 - 3 + 9 EIRP = 22.99 dBm

Rounding up to the nearest integer, we get 23 dBm as the EIRP at the antenna element12. References: CWNA-109 Study Guide, Chapter 2: Radio Frequency Fundamentals, page 92; CWNA-108 Study Guide, Chapter 2: Radio Frequency Fundamentals, page 88.

What should be inspected to verify proper configuration is DNS. DNS stands for Domain Name System and is a service that resolves hostnames to IP addresses. In a controller-based AP deployment, DNS can be used to help the AP locate the controller by using a predefined hostname such as CISCO-CAPWAP-CONTROLLER or aruba-master. The AP sends a DNS query for this hostname and receives an IP address of the controller as a response. Therefore, if DNS is not configured properly or if there is no DNS entry for the controller hostname, the AP may not be able to locate the controller. NTP, BOOTP, and AP hosts file are not relevant for this scenario. References: [CWNP Certified Wireless Network Administrator Official Study Guide: Exam CWNA-107], page 374; [CWNA: Certified Wireless Network Administrator Official Study Guide: Exam CWNA-106], page 364.

Patch and panel antennas are directional antenna types that are commonly used by indoor Wi-Fi devices in a MIMO multiple spatial stream implementation. These antennas have a flat rectangular shape and can be mounted on walls or ceilings to provide coverage in a specific direction. They have a moderate gain and a relatively wide beamwidth, making them suitable for multipath environments where signals can reflect off different surfaces and create multiple spatial streams. Patch and panel antennas can also support polarization diversity, which means they can transmit and receive both horizontally and vertically polarized waves, increasing the MIMO performance. References: 1, Chapter 2, page 72; 2, Section 2.4

 The cipher suite specified by the 802.11-2016 standard and is not deprecated is Counter Mode with CBC-MAC Protocol (CCMP). CCMP is an encryption protocol that uses Advanced Encryption Standard (AES) as the underlying cipher and provides confidentiality, integrity, and origin authentication for wireless data. CCMP is the mandatory encryption protocol for WPA2 and WPA3. References: [CWNP Certified Wireless Network Administrator Official Study Guide: Exam CWNA-107], page 295; [IEEE Standard for Information technology–Telecommunications and information exchange between systems Local and metropolitan area networks–Specific requirements - Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications], page 1560.

The term used to describe the problem in this configuration is Co-Channel Interference (CCI)1. CCI occurs when multiple access points are on the same or overlapping channels, causing interference and degradation in network performance1. In this case, one AP is on channel 1 and the other is on channel 2, which are overlapping channels, leading to CCI1.

 The frame type that is used to reserve the wireless medium for the transmission of high data rate frames that may not be understood by all clients connected to the BSS is RTS. RTS stands for Request to Send and is a control frame that is sent by a station to request access to the medium for a specified duration. The RTS frame contains the source and destination MAC addresses, as well as a Network Allocation Vector (NAV) value that indicates how long the medium will be occupied. The destination station responds with a Clear to Send (CTS) frame that echoes the NAV value and grants permission to the source station. All other stations in the BSS hear either the RTS or CTS frame and update their NAV timers accordingly, deferring their transmissions until the medium is free. The RTS/CTS mechanism can be used to prevent hidden node problems, reduce collisions, and protect high data rate frames that use features such as 802.11n or 802.11ac that may not be compatible with legacy stations. ACK, Beacon, and PS-Poll are not used to reserve the medium for high data rate frames. References: [CWNP Certified Wireless Network Administrator Official Study Guide: Exam CWNA-107], page 112; [CWNA: Certified Wireless Network Administrator Official Study Guide: Exam CWNA-106], page 102.