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Question 361.

Which RF parameter describes the amount of power actually delivered by a transmitter before antenna gain and cable loss are considered?

1. Transmit power
   2. EIRP
   3. SNR
   4. RSSI

Correct Answer: 1. Transmit power

Explanation:

Transmit power is the RF power generated by the radio before external antenna gain and cable or connector losses are applied. It is commonly expressed in dBm or milliwatts. EIRP represents the effective radiated power after system losses and antenna gain are considered. SNR compares desired signal strength to the noise floor, while RSSI indicates received signal strength. WLAN professionals use transmit power as one component of the overall link budget. It should be configured with client capabilities, regulatory limits, cell size, and channel reuse in mind rather than simply set to the maximum available value.

Question 362.

Which measurement represents effective radiated power after accounting for transmit power, cable loss, and antenna gain?

1. RSSI
   2. EIRP
   3. Noise floor
   4. SNR

Correct Answer: 2. EIRP

Explanation:

Effective Isotropic Radiated Power, or EIRP, represents the effective power radiated in the direction of maximum antenna gain after accounting for transmitter output, cable loss, connector loss, and antenna gain. A simplified formula is transmit power minus system losses plus antenna gain. RSSI and SNR describe receive-side conditions, while the noise floor is the background RF energy level. EIRP is important for regulatory compliance because many jurisdictions impose limits on effective radiated power. It is especially important when external high-gain antennas are used, since antenna gain can significantly increase effective radiated power even when transmitter output remains unchanged.

Question 363.

Which WLAN planning concept evaluates whether enough RF energy will reach a receiver for reliable communication?

1. VLAN design
   2. DHCP planning
   3. Link budget
   4. DNS planning

Correct Answer: 3. Link budget

Explanation:

A link budget accounts for gains and losses throughout the RF path to determine whether the received signal will be strong enough for reliable communication. Typical inputs include transmit power, cable and connector loss, antenna gain, free-space path loss, receiving antenna gain, and receiver sensitivity. A fade margin is also commonly added to improve reliability. VLANs, DHCP, and DNS are network-layer services and do not determine physical RF viability. Link budgets are particularly important for outdoor point-to-point links, though the same principles also help WLAN professionals understand indoor coverage and radio performance.

Question 364.

Which factor should be added to a link budget to provide extra reliability against temporary signal fading and environmental change?

1. Additional SSIDs
   2. Longer DHCP lease
   3. Wider channel only
   4. Fade margin**

Correct Answer: 4. Fade margin

Explanation:

Fade margin provides an extra RF signal buffer above the minimum required receive level. It helps maintain reliability when conditions change because of multipath fading, weather, foliage, movement, small alignment errors, or other environmental effects. A link that operates exactly at the receiver’s minimum sensitivity may work under ideal conditions but become unstable with only a small amount of additional loss. SSIDs, DHCP timing, and channel width do not provide this type of reliability reserve. Outdoor links especially benefit from planned fade margin because environmental conditions can change considerably over time.

Question 365.

Which RF characteristic should be checked if an outdoor point-to-point bridge has strong transmit power but unexpectedly weak received signal because of antenna orientation?

1. Polarization
   2. DHCP configuration
   3. VLAN tagging
   4. DNS response time

Correct Answer: 1. Polarization

Explanation:

Polarization describes the orientation of the electric field of an RF wave. If the transmitting and receiving antennas are oriented with significantly different polarization, signal loss can occur even when transmit power and line of sight are otherwise good. This is especially important for directional outdoor antennas because installers control their mounting orientation directly. DHCP, VLANs, and DNS do not affect RF coupling between antennas. Correct polarization alignment, antenna aiming, Fresnel clearance, cable quality, and mounting stability should all be verified when troubleshooting an unexpectedly weak outdoor bridge.

Question 366.

Which condition can occur when an AP transmits at 23 dBm but a mobile client can transmit only at 14 dBm?

1. The client automatically increases power to 23 dBm
   2. An asymmetric link may develop
   3. The AP stops sending beacons
   4. The client disables roaming

Correct Answer: 2. An asymmetric link may develop

Explanation:

An asymmetric link can occur when the AP is much more powerful than the client. The client may hear the AP from a relatively long distance, but its weaker uplink frames may not reach the AP reliably. This can result in retries, poor throughput, intermittent connectivity, and sticky-client behavior. The client does not automatically increase its transmit power to match the AP. Good WLAN design should therefore consider the transmit capabilities of production clients and configure AP power accordingly. Balanced links support more predictable cell boundaries, roaming, and bidirectional performance.

Question 367.

Which RF measurement should be examined when a client has strong RSSI but still struggles to decode frames because of a high background noise level?

1. EIRP
   2. Antenna gain
   3. SNR
   4. Channel width

Correct Answer: 3. SNR

Explanation:

SNR compares the strength of the desired signal to the surrounding noise floor. A client can have a strong RSSI and still experience poor performance if the noise level is also high. For example, -55 dBm RSSI sounds strong, but if the noise floor is -62 dBm, the SNR is only 7 dB and decoding may be difficult. EIRP and antenna gain describe transmit-side characteristics, while channel width does not directly express signal quality. SNR is therefore one of the best indicators of how distinguishable the desired transmission is from unwanted background RF energy.

Question 368.

Which type of WLAN interference is usually associated with two nearby transmitters using partially overlapping frequencies?

1. Hidden-node interference
   2. Co-channel contention
   3. Multipath only
   4. Adjacent-channel interference**

Correct Answer: 4. Adjacent-channel interference

Explanation:

Adjacent-channel interference occurs when nearby transmitters use frequency ranges that partially overlap. This is particularly problematic in 2.4 GHz because many channel numbers overlap substantially. Unlike same-channel devices, which often coordinate through normal CSMA/CA contention, partially overlapping transmitters may interfere more destructively and cause corrupted frames and retries. Proper channel planning should therefore avoid partially overlapping channels whenever possible. Hidden nodes, multipath, and co-channel contention are distinct WLAN phenomena with different causes and mitigation techniques.

Question 369.

Which type of WLAN interaction occurs when two nearby BSSs use exactly the same channel and can hear each other?

1. Co-channel contention
   2. Adjacent-channel interference
   3. Polarization mismatch
   4. Refraction

Correct Answer: 1. Co-channel contention

Explanation:

When two BSSs use the same channel and are within carrier-sense range, their devices generally share airtime through CSMA/CA. This is referred to as co-channel contention. It reduces available airtime because each BSS must wait while the other transmits. Adjacent-channel interference involves partially overlapping channels and is usually more destructive. Polarization mismatch and refraction are physical RF phenomena. Co-channel reuse is unavoidable in large WLANs, but excessive overlap should be minimized with appropriate AP placement, power levels, channel width, and frequency planning.

Question 370.

Which design choice is most likely to reduce the number of independent channels available in a 5 GHz WLAN?

1. Narrowing channels to 20 MHz
   2. Using wider channels such as 80 MHz
   3. Reducing transmit power
   4. Disabling one SSID

Correct Answer: 2. Using wider channels such as 80 MHz

Explanation:

Wider channels consume more spectrum and therefore reduce the number of independent channels available for reuse. An 80 MHz channel uses the equivalent spectrum of four 20 MHz channels. In dense deployments, this can force more APs to reuse the same wide channels, increasing co-channel contention. Narrower channels often improve aggregate capacity even though they provide lower peak PHY rates per client. Reducing transmit power and SSID count can improve other aspects of WLAN efficiency but do not directly consume channel spectrum in the same way. Channel width should therefore be selected based on density and reuse requirements.

Question 371.

Which 802.11 frame is transmitted periodically by an access point and can be used by clients during passive scanning?

1. Beacon
   2. ACK
   3. RTS
   4. CTS

Correct Answer: 1. Beacon

Explanation:

Beacon frames are management frames transmitted periodically by an access point to advertise BSS information. During passive scanning, clients listen for these frames rather than transmitting Probe Requests. Beacons include information about capabilities, supported rates, timing, and security parameters. ACK, RTS, and CTS are control frames used for reliability and medium access. Beacon traffic consumes airtime, especially when many SSIDs are configured or basic rates are low. For this reason, WLAN architects should avoid excessive SSIDs and consider management overhead when planning dense environments.

Question 372.

Which management frame is sent by a client when actively searching for nearby WLANs?

1. Association Response
   2. Probe Request
   3. Block ACK
   4. Deauthentication

Correct Answer: 2. Probe Request

Explanation:

During active scanning, a client transmits Probe Request management frames on supported channels to discover nearby WLANs. Access points can respond with Probe Response frames. This differs from passive scanning, where the client listens for Beacons without transmitting discovery requests. Association Responses are part of the join process, Block ACK improves acknowledgment efficiency, and Deauthentication terminates authentication state. Scanning behavior plays an important role in roaming because the client must often identify candidate BSSs before deciding whether to leave the current AP.

Question 373.

Which control frame confirms successful receipt of many unicast Wi-Fi transmissions?

1. Probe Response
   2. Beacon
   3. ACK
   4. Authentication

Correct Answer: 3. ACK

Explanation:

An ACK control frame confirms that a unicast transmission was received successfully. If the sender does not receive the expected ACK, it may retransmit the frame. This mechanism improves reliability over the RF medium, where collisions, interference, and fading can cause losses. Probe Response, Beacon, and Authentication are management frames. While ACKs are essential, they consume airtime. High retry rates can therefore reduce WLAN throughput significantly because both failed transmissions and their retransmissions occupy the shared medium. Retry behavior is an important indicator during WLAN troubleshooting.

Question 374.

Which 802.11 control exchange can help mitigate hidden-node collisions?

1. Beacon/Probe Response
   2. Association Request/Response
   3. EAPOL exchange
   4. RTS/CTS**

Correct Answer: 4. RTS/CTS

Explanation:

RTS/CTS can help reduce collisions caused by hidden nodes. A station sends an RTS frame, the receiver responds with CTS, and other stations hearing the control exchange update their virtual carrier-sense state and defer transmission. This is useful when two transmitting clients cannot hear each other but can both reach the same AP. The mechanism adds overhead, so it should not be used unnecessarily. Beacon and association exchanges serve discovery and connectivity purposes, while EAPOL is used in enterprise authentication. RTS/CTS is specifically a medium reservation technique.

Question 375.

Which value does a station maintain to represent the time for which the medium is virtually reserved?

1. NAV
   2. DHCP lease timer
   3. DNS TTL
   4. TCP window

Correct Answer: 1. NAV

Explanation:

The Network Allocation Vector, or NAV, is used for virtual carrier sensing in 802.11. A station can update the NAV based on duration information in received frames and treat the medium as busy until the indicated interval expires. This helps coordinate transmissions even when a station cannot physically hear every frame in the exchange. DHCP lease timers, DNS TTL values, and TCP windows are higher-layer concepts. NAV behavior is especially important during multi-frame exchanges such as RTS/CTS because it helps surrounding stations defer until the reserved transmission sequence is complete.

Question 376.

Which WMM category is intended for normal, non-prioritized traffic such as ordinary web browsing?

1. AC_VO
   2. AC_BE
   3. AC_VI
   4. AC_BK

Correct Answer: 2. AC_BE

Explanation:

AC_BE stands for Best Effort and is intended for ordinary traffic that does not require special priority. Voice receives the highest normal WMM priority, video receives elevated priority, and background traffic receives the least favorable contention parameters. Best Effort commonly handles general web browsing and many standard application flows. WMM modifies how traffic categories contend for airtime but does not guarantee bandwidth. Even correctly classified Best Effort traffic can perform poorly if the channel is highly utilized or if interference causes significant retransmissions.

Question 377.

Which WMM category is normally given the lowest priority?

1. Voice
   2. Video
   3. Background
   4. Best Effort

Correct Answer: 3. Background

Explanation:

The Background access category is intended for traffic that can tolerate delay, such as non-urgent synchronization or background transfers. It receives the least favorable contention parameters among the standard WMM categories. Voice and video are prioritized because of their sensitivity to delay and jitter, while Best Effort handles normal application traffic. Background prioritization helps keep delay-tolerant traffic from competing too aggressively with real-time applications. However, QoS does not increase total channel capacity; the underlying WLAN must still have adequate airtime and healthy RF conditions.

Question 378.

Which roaming enhancement provides radio resource measurements and neighbor information?

1. 802.11r
   2. 802.11k
   3. 802.11v
   4. 802.11i

Correct Answer: 2. 802.11k

Explanation:

802.11k provides radio resource measurement functions and can provide clients with information about neighboring BSSs. This helps compatible clients discover roaming candidates more efficiently instead of scanning every channel blindly. 802.11r focuses on Fast BSS Transition, while 802.11v provides network-management features such as BSS Transition Management. 802.11i addresses WLAN security. These roaming enhancements are complementary, but the client still makes the final decision about when and where to roam. Their benefit depends on client support, RF design, and implementation quality.

Question 379.

Which security architecture should be selected when an enterprise requires centralized authentication and unique credentials for users or devices?

1. 802.1X/EAP with RADIUS
   2. One shared PSK
   3. Open WLAN
   4. Static WEP

Correct Answer: 1. 802.1X/EAP with RADIUS

Explanation:

802.1X/EAP with RADIUS provides centralized enterprise authentication and supports unique credentials or certificates for users and devices. This improves accountability, revocation, and policy control compared with a shared password. Open WLANs do not provide equivalent authentication, while WEP is obsolete. A shared PSK may be suitable for some small or specialized deployments but becomes difficult to manage at scale. Enterprise deployments should also enforce proper server-certificate validation and maintain reliable authentication infrastructure because certificate or RADIUS failures can prevent clients from connecting even when RF conditions are healthy.

Question 380.

A user has strong RSSI, good SNR, successful association, successful authentication, and a valid IP address, but web pages load slowly only during peak hours. Which area should be investigated first?

1. Antenna polarization
   2. Association status
   3. EAP credentials
   4. Airtime utilization, contention, and capacity**

Correct Answer: 4. Airtime utilization, contention, and capacity

Explanation:

The client has already demonstrated that RF coverage, association, authentication, and IP configuration are functioning. If performance degrades primarily during peak usage, the most likely issue is shared-medium capacity. The administrator should examine channel utilization, client density, co-channel contention, application demand, retries, channel widths, and neighboring BSS activity. High RSSI and good SNR do not create additional airtime. Peak-hour slowdowns are therefore commonly capacity problems rather than basic connectivity failures. A layered troubleshooting process helps avoid wasting time revisiting stages that have already been shown to work correctly.