CWNP CWNA-109 Practice Test - Questions Answers

What prevents each station from using all the airtime when other client stations are actively communicating in the same BSS isCSMA/C

A . CSMA/CA stands for Carrier Sense Multiple Access with Collision Avoidance and is a media access control method used by WLAN devices to share the wireless medium. CSMA/CA works by having each station sense the medium before transmitting a frame. If the medium is busy (i.e., another station is transmitting), the station defers its transmission until the medium is idle. If the medium is idle, the station waits for a random backoff period before transmitting. This way, CSMA/CA reduces the chances of collisions and ensures fair access to the medium for all stations. CSMA/CA also uses positive acknowledgements to confirm successful transmissions and retransmissions to recover from errors. CSMA/CD, DOS prevention, and OFDMA are not used by WLAN devices in a BSS.Reference:[CWNP Certified Wireless Network Administrator Official Study Guide: Exam CWNA-109], page 108; [CWNA: Certified Wireless Network Administrator Official Study Guide: Exam CWNA-109], page 98.

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 isRTS. 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.Reference:[CWNP Certified Wireless Network Administrator Official Study Guide: Exam CWNA-109], page 112; [CWNA: Certified Wireless Network Administrator Official Study Guide: Exam CWNA-109], page 102.

The RF energy that exists in the environment from intentional and unintentional RF radiators that forms the baseline above which the intentional signal of your WLAN must exist is the best explanation of the noise floor noted in the report. The noise floor is a term that describes the level of background noise or interference in a wireless channel or band. The noise floor is measured in dBm (decibel-milliwatts) and it represents the minimum signal strength that can be detected or received by a wireless device. The noise floor is influenced by various factors, such as the sensitivity of the receiver, the antenna gain, the cable loss, and the ambient RF environment. The ambient RF environment consists of intentional and unintentional RF radiators that emit RF energy in the wireless spectrum. Intentional RF radiators are devices that are designed to transmit RF signals for communication purposes, such as Wi-Fi access points, Bluetooth devices, microwave ovens, or cordless phones. Unintentional RF radiators are devices that are not designed to transmit RF signals but generate electromagnetic radiation as a by-product of their operation, such as USB 3 devices, PC power supplies, or fluorescent lights. The noise floor affects WLAN performance and quality because it determines the minimum signal-to-noise ratio (SNR) that is required for a successful wireless transmission. SNR is the difference between the signal strength of the desired signal and the noise floor of the channel. SNR is also measured in dB and it indicates how much the signal stands out from the noise. A higher SNR means a better signal quality and a lower bit error rate. A lower SNR means a worse signal quality and a higher bit error rate. Therefore, to achieve a reliable WLAN connection, the intentional signal of your WLAN must exist above the noise floor by a certain margin that depends on the data rate and modulation scheme used. The other options are not accurate or complete explanations of the noise floor noted in the report. The noise caused by elevators, microwave ovens, and video transmitters is not the noise floor but rather examples of interference sources that contribute to the noise floor. The extra energy radiated by access points and client devices beyond that intended for the signal is not the noise floor but rather an example of spurious emissions that cause interference to other devices or channels. The energy radiated by flooring materials that causes interference in the 2.4 GHz and 5 GHz bands is not the noise floor but rather an example of attenuation or reflection that reduces or changes the direction of the signal.Reference:CWNA-109 Study Guide, Chapter 5: Radio Frequency Signal and Antenna Concepts, page 139

In a public Wi-Fi hotspot, like the one Lynne runs in his hotel, ensuring customer security against active attacks is crucial. Active attacks involve unauthorized access, eavesdropping, or manipulation of the network traffic. To mitigate such threats, an effective and practical step is:

Station-to-Station Traffic Blocking: Also known as client isolation, this feature prevents direct communication between devices connected to the Wi-Fi network. By enabling this on the access points, Lynne can significantly decrease the likelihood of active attacks like man-in-the-middle (MITM) attacks, where an attacker intercepts and possibly alters the communication between two parties.

The other options, while beneficial for network security, might not be as straightforward or practical for Lynne's situation:

Network Access Control (NAC) requires a more complex infrastructure and management, which might not be ideal for a small hotel setup.

Implementing an SSL VPN adds an extra layer of security but might complicate the login process for users, potentially affecting the user experience.

Requiring EAP-FAST authentication provides secure authentication but may not be feasible for transient customers who expect quick and easy network access.

Therefore, enabling station-to-station traffic blocking is a practical and efficient measure that Lynne can implement to enhance customer security on the Wi-Fi network.

CWNA Certified Wireless Network Administrator Official Study Guide: Exam CWNA-109, by David D. Coleman and David A. Westcott.

Best practices for securing a wireless network in a public hotspot environment.

https://www.wlanmall.com/what-is-a-wireless-bridge/

Wireless bridging is a WLAN technology role that allows two or more networks to be connected wirelessly over a distance. A wireless bridge consists of two or more APs that are configured to operate in bridge mode and use directional antennas to establish a point-to-point or point-to-multipoint link. Wireless bridging can support high data rates and is suitable for scenarios where running cables is impractical or expensive.To create a wireless link between two buildings on a single campus that supports at least 150 Mbps data rates, wireless bridging is an appropriate solution678.Reference:CWNA-109 Study Guide, Chapter 6: Wireless LAN Devices and Topologies, page 271;CWNA-109 Study Guide, Chapter 6: Wireless LAN Devices and Topologies, page 265;Wi-Fi Wireless Bridging Explained.

PoE stands for Power over Ethernet, which is a technology that allows network devices to receive power and data over the same Ethernet cable. PoE eliminates the need for separate power adapters or outlets for devices such as IP phones, cameras, or APs. PoE requires two types of devices: PSE (Power Sourcing Equipment) and PD (Powered Device). A PSE is a device that provides power to the Ethernet cable, such as a switch, injector, or splitter. A PD is a device that receives power from the Ethernet cable, such as an IP phone, camera, or AP.When implementing PoE, a switch plays the role of a PSE910.Reference:CWNA-109 Study Guide, Chapter 7: Power over Ethernet (PoE), page 293;CWNA-109 Study Guide, Chapter 7: Power over Ethernet (PoE), page 287.

PoE has different standards that define different power levels for PSEs and PDs. The original standard, IEEE 802.3af, defines two classes of PSEs: Class 3 (15.4 W) and Class 4 (30 W). The newer standard, IEEE 802.3at, also known as PoE+, defines four classes of PSEs: Class 0 (15.4 W), Class 1 (4 W), Class 2 (7 W), and Class 3 (12.95 W). The power level received at the PD is always lower than the power level provided by the PSE, due to cable resistance and power dissipation. The IEEE standards specify the minimum power level that must be received at the PD for each class of PSE.For a Class 4 PSE, the minimum power level received at the PD is 25.5 W910.Reference:CWNA-109 Study Guide, Chapter 7: Power over Ethernet (PoE), page 295;CWNA-109 Study Guide, Chapter 7: Power over Ethernet (PoE), page 289.

DHCP (Dynamic Host Configuration Protocol) is a commonly used method to locate the controllers by the APs in a WLAN that is implemented using wireless 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 APs 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. This way, the APs can discover the wireless controller and establish a connection with it.Alternatively, the APs can also use other methods to locate the wireless controller, such as DNS (Domain Name System), broadcast or multicast discovery, or manual configuration.Reference:1, Chapter 8, page 309;2, Section 5.2

FT (Fast Transition) is an IEEE 802.11 standard method for fast roaming. FT is defined in the IEEE 802.11r amendment and is also known as Fast BSS Transition (FBT) or Fast Secure Roaming. FT is a feature that allows a client station to quickly switch from one AP to another within the same ESS (Extended Service Set) without having to re-authenticate and re-associate with each AP. This reduces the latency and packet loss that may occur during roaming, thus improving the user experience and maintaining the security of the connection. FT works by using pre-authentication and key caching mechanisms that allow the client station and the APs to exchange security information before the actual roaming occurs.This way, when the client station decides to roam to a new AP, it can use a fast reassociation request and response that contain only a few fields, instead of a full authentication and association exchange that require more time and data.Reference:1, Chapter 9, page 367;2, Section 6.3