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Question 241.

Which WLAN design parameter most directly affects how many independent 20 MHz channels are available for reuse within a frequency band?

1. Channel width
   2. SSID length
   3. DHCP lease duration
   4. RADIUS timeout

Correct Answer: 1. Channel width

Explanation:

Channel width directly affects how much spectrum each WLAN cell consumes. Using narrower channels such as 20 MHz leaves more independent channels available for reuse, while wider channels such as 40, 80, or 160 MHz consume more spectrum and reduce reuse opportunities. This is especially important in dense enterprise environments where aggregate capacity is often limited by airtime contention rather than by the peak rate of a single client. SSID length, DHCP lease duration, and RADIUS timeout do not determine channel availability. WLAN designers should therefore select channel width based on density, application requirements, available spectrum, and client capabilities rather than automatically choosing the widest possible setting.

Question 242.

Which condition is most likely when two nearby APs use the same channel and are within carrier-sense range of one another?

1. Adjacent-channel interference
   2. Co-channel contention
   3. Complete RF isolation
   4. Automatic full-duplex operation

Correct Answer: 2. Co-channel contention

Explanation:

When two nearby APs and their clients operate on the same channel and can detect one another, they typically share the medium through normal 802.11 contention. This is commonly called co-channel contention. Devices defer and wait for transmission opportunities, which reduces the amount of airtime available to each BSS. Adjacent-channel interference is different because overlapping frequencies can interfere without the same orderly coordination. Wi-Fi is not automatically full duplex, and same-channel cells do not become isolated simply because they belong to different APs. Effective WLAN design tries to limit unnecessary same-channel overlap while preserving coverage and capacity.

Question 243.

Which factor is most likely to increase the amount of airtime consumed by a client transferring the same file?

1. Higher PHY rate
   2. Better SNR
   3. Lower PHY rate
   4. Higher antenna gain at the receiver

Correct Answer: 3. Lower PHY rate

Explanation:

A lower PHY rate requires more transmission time to move the same amount of data. Because Wi-Fi is a shared medium, that additional transmission time consumes more airtime and prevents other stations on the same channel from transmitting. This is one reason distant or poorly performing clients can disproportionately affect overall WLAN capacity. Higher PHY rates generally reduce airtime consumption for the same payload, assuming retries remain low. Better SNR and appropriate antenna performance may help support those higher rates. Airtime, rather than raw bandwidth alone, is the key shared resource in WLAN capacity planning.

Question 244.

Which action is most likely to improve a WLAN where many clients remain connected to distant APs and roam too late?

1. Increase every AP to maximum power
   2. Add more SSIDs
   3. Disable acknowledgments
   4. Review cell size, transmit power, overlap, and client roaming behavior**

Correct Answer: 4. Review cell size, transmit power, overlap, and client roaming behavior

Explanation:

Sticky-client behavior often results from a combination of oversized cells, high AP transmit power, client roaming thresholds, and insufficiently attractive candidate APs. Increasing transmit power usually makes the problem worse because the original AP remains audible for longer. Additional SSIDs do not improve roaming, and acknowledgments are fundamental to reliable 802.11 operation. A proper investigation should evaluate AP power, cell overlap, signal levels along roam paths, candidate visibility, client-specific roaming behavior, and support for features such as 802.11k, 802.11r, and 802.11v. Roaming remains primarily a client decision, so representative endpoint testing is essential.

Question 245.

Which 802.11 amendment is most closely associated with radio resource measurements and neighbor information?

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

Correct Answer: 1. 802.11k

Explanation:

802.11k adds radio resource measurement capabilities and can provide information that helps clients understand the nearby WLAN environment. Neighbor information can reduce the need for a client to scan every possible channel when looking for roaming candidates. 802.11r focuses on Fast BSS Transition, 802.11v adds network-management functions such as BSS Transition Management, and 802.11i introduced stronger WLAN security. These features are often discussed together because they can collectively improve roaming behavior, but each solves a different problem. Actual results depend on both infrastructure and client support.

Question 246.

Which amendment is designed to reduce authentication-related roaming delay between BSSs?

1. 802.11e
   2. 802.11r
   3. 802.11d
   4. 802.11h

Correct Answer: 2. 802.11r

Explanation:

802.11r introduced Fast BSS Transition, which is designed to reduce the time required for security and authentication-related processing during a roam. This is particularly valuable for voice and other real-time applications that are sensitive to brief interruptions. 802.11e introduced QoS-related enhancements, 802.11d addressed regulatory information, and 802.11h provided spectrum-management capabilities. Even when 802.11r is available, WLAN engineers should validate actual client behavior because some devices may not support the feature or may implement it differently.

Question 247.

Which amendment includes BSS Transition Management, allowing the network to suggest a better BSS to a client?

1. 802.11n
   2. 802.11ac
   3. 802.11v
   4. 802.11g

Correct Answer: 3. 802.11v

Explanation:

802.11v includes wireless network-management enhancements such as BSS Transition Management. Infrastructure can use this mechanism to provide a client with information or recommendations about alternative BSSs. The client still makes the final decision about whether to roam. 802.11n and 802.11ac are primarily associated with PHY and throughput improvements, while 802.11g is an older 2.4 GHz PHY. BSS Transition Management can complement 802.11k and 802.11r, but the practical benefit depends on client support, driver behavior, RF design, and overall roaming conditions.

Question 248.

Which protocol is commonly used between a WLAN authenticator and a centralized authentication server in an enterprise 802.1X deployment?

1. DHCP
   2. DNS
   3. ARP
   4. RADIUS**

Correct Answer: 4. RADIUS

Explanation:

RADIUS is commonly used between the WLAN authenticator and the centralized authentication server in enterprise 802.1X deployments. The access point or controller relays authentication information to the RADIUS server, which validates the user’s or device’s credentials according to the configured EAP method and identity infrastructure. DHCP, DNS, and ARP support network addressing and name-resolution functions rather than enterprise authentication. RADIUS logs are especially useful during troubleshooting because they can reveal rejected credentials, certificate issues, policy failures, or problems communicating with backend identity systems.

Question 249.

Which component acts as the supplicant in a typical enterprise WLAN authentication exchange?

1. Wireless client
   2. RADIUS server
   3. DNS server
   4. Ethernet uplink

Correct Answer: 1. Wireless client

Explanation:

The supplicant is the client device or software seeking authenticated access to the network. It participates in EAP exchanges and presents the required credentials or certificates. The WLAN infrastructure commonly acts as the authenticator, while a RADIUS server performs the authentication-server role. DNS and Ethernet uplinks are not supplicants. Understanding these roles is important because an authentication failure can originate from the client configuration, WLAN infrastructure, certificates, RADIUS policy, or backend identity services. Effective troubleshooting often requires correlating client behavior, packet captures, and RADIUS logs.

Question 250.

Which component most commonly acts as the authenticator in an 802.1X WLAN?

1. DNS server
   2. Access point or WLAN infrastructure
   3. DHCP server
   4. File server

Correct Answer: 2. Access point or WLAN infrastructure

Explanation:

In a typical enterprise WLAN, the access point or centralized WLAN infrastructure acts as the authenticator. It controls access to the network and relays EAP authentication information between the client supplicant and the authentication server, commonly using RADIUS on the backend. The DHCP server provides IP configuration, DNS resolves names, and file servers provide application services. Recognizing the supplicant, authenticator, and authentication-server roles helps administrators isolate failures. If association succeeds but enterprise authentication fails, the problem may exist at the client, authenticator, RADIUS server, certificate infrastructure, or identity store.

Question 251.

Which WLAN security feature is specifically intended to protect selected management frames from spoofing or tampering?

1. WPA Personal
   2. Hidden SSID
   3. Protected Management Frames
   4. DHCP snooping

Correct Answer: 3. Protected Management Frames

Explanation:

Protected Management Frames, or PMF, provide cryptographic protection for selected robust management frames, including important deauthentication and disassociation exchanges. This reduces the ability of an attacker to forge those frames and disrupt client connectivity. A hidden SSID does not provide cryptographic security, and DHCP snooping is a wired switching protection mechanism. WPA Personal secures data traffic using shared credentials but does not by itself describe management-frame protection. PMF is increasingly important in modern WLAN security and is required in certain newer security modes.

Question 252.

Which authentication approach offers better individual accountability than giving every employee the same pre-shared key?

1. Open authentication
   2. Static WEP
   3. MAC filtering
   4. 802.1X/EAP with individual credentials**

Correct Answer: 4. 802.1X/EAP with individual credentials

Explanation:

802.1X/EAP can provide unique credentials or certificates for individual users and devices. This improves accountability because access can be audited and revoked selectively without changing one shared password for everyone. Open authentication provides no comparable identity assurance, WEP is obsolete and insecure, and MAC filtering can be bypassed because addresses are easily observed and spoofed. Enterprise authentication also supports centralized policy enforcement and can integrate with directory services and certificate infrastructure. Proper certificate validation and RADIUS redundancy are important for maintaining both security and availability.

Question 253.

Which security practice is especially important when using tunneled EAP methods that rely on server certificates?

1. Validate the authentication server certificate and trusted CA
   2. Disable certificate checks for convenience
   3. Hide the SSID
   4. Use the same username on every device

Correct Answer: 1. Validate the authentication server certificate and trusted CA

Explanation:

Clients should validate the authentication server’s certificate and verify that it chains to an approved certificate authority. Without this validation, a rogue authentication server may impersonate the legitimate infrastructure and attempt to capture credentials. Disabling certificate checks creates a serious security weakness, while hiding the SSID provides no meaningful protection against impersonation. Proper certificate trust should be centrally configured where possible so users are not prompted to make manual trust decisions. Certificate expiration, naming, revocation, and trust-chain configuration should also be monitored as part of WLAN operations.

Question 254.

Which tool is most appropriate for analyzing EAPOL exchanges and 802.11 authentication frames?

1. Spectrum analyzer only
   2. Wireless protocol analyzer
   3. Cable certifier only
   4. DNS query tool

Correct Answer: 2. Wireless protocol analyzer

Explanation:

A wireless protocol analyzer can capture and decode 802.11 management frames and EAPOL exchanges, making it highly useful for troubleshooting enterprise WLAN authentication. Administrators can examine the sequence of frames, status codes, retransmissions, and authentication messages. A spectrum analyzer provides physical-layer visibility into RF energy but cannot decode the protocol details of EAPOL exchanges. Cable certifiers and DNS tools operate at other layers. For enterprise authentication problems, protocol captures are often most effective when correlated with RADIUS server logs and exact timestamps.

Question 255.

Which tool is best for identifying RF energy from a device that does not transmit valid 802.11 frames?

1. RADIUS log viewer
   2. DHCP console
   3. Spectrum analyzer
   4. ARP table

Correct Answer: 3. Spectrum analyzer

Explanation:

A spectrum analyzer shows RF energy across a frequency range whether or not the signal can be decoded as Wi-Fi. This makes it useful for finding non-802.11 interference sources such as certain industrial devices, microwave ovens, analog transmitters, or poorly shielded electronics. RADIUS logs provide authentication information, DHCP consoles show address allocation, and ARP tables show network-layer mappings. Protocol analyzers are excellent for Wi-Fi frame analysis but may not identify the nature of non-Wi-Fi RF energy. Spectrum analysis therefore provides complementary physical-layer visibility.

Question 256.

Which survey method is most appropriate before installation when the building design is known and software is used to estimate RF coverage?

1. Validation survey
   2. Troubleshooting survey
   3. AP failure analysis
   4. Predictive survey**

Correct Answer: 4. Predictive survey

Explanation:

A predictive survey uses floor plans, assumed wall attenuation, AP specifications, antenna patterns, transmit power, and software RF modeling to estimate coverage before deployment. It is efficient for initial design and can help determine approximate AP locations and channel plans. However, it depends on assumptions and cannot perfectly represent actual construction materials, furniture, interference, or client behavior. For that reason, predictive design should normally be followed by post-deployment validation. Troubleshooting and AP failure analysis are reactive processes rather than pre-installation design methods.

Question 257.

Which survey technique uses a temporary AP at proposed mounting locations to collect actual RF measurements before permanent installation?

1. AP-on-a-stick survey
   2. DNS survey
   3. DHCP survey
   4. Logical VLAN survey

Correct Answer: 1. AP-on-a-stick survey

Explanation:

An AP-on-a-stick survey uses a temporary access point placed at proposed locations and heights to measure real RF propagation before permanent installation. It is particularly useful in environments where predictive models may be unreliable because of unusual building materials, metal shelving, machinery, high ceilings, or complex physical layouts. The temporary AP should use settings and antennas representative of the final design so measurements are meaningful. DNS, DHCP, and VLAN reviews do not measure RF propagation. AP-on-a-stick work is more labor-intensive than prediction but can provide valuable empirical data.

Question 258.

Which validation method is most appropriate for testing an enterprise voice WLAN after deployment?

1. Check only AP uptime
   2. Test roaming and application performance with representative voice clients
   3. Review only controller configuration
   4. Measure only RSSI beside each AP

Correct Answer: 2. Test roaming and application performance with representative voice clients

Explanation:

Voice WLAN validation should use representative production devices while moving along realistic roam paths. Testing should examine RSSI, SNR, roaming delay, packet loss, latency, jitter, candidate AP visibility, and call continuity. AP uptime and controller configuration confirm only that infrastructure is operational, while measuring RSSI beside each AP does not prove roaming or application quality. Client behavior is especially important because different handsets may use different roaming thresholds and scanning strategies. Real-device testing therefore provides the strongest evidence that the deployed WLAN satisfies voice requirements.

Question 259.

Which statement best explains why a predictive WLAN design should normally be validated after installation?

1. Real materials, interference, installation differences, and client behavior may differ from the model
   2. Predictive software never uses floor plans
   3. APs cannot transmit until validation is complete
   4. Validation changes the IEEE standard

Correct Answer: 1. Real materials, interference, installation differences, and client behavior may differ from the model

Explanation:

Predictive models are based on assumptions about wall attenuation, AP placement, antenna behavior, transmit power, and the RF environment. Real buildings can differ from those assumptions because of construction details, furniture, people, neighboring WLANs, industrial equipment, and installation variations. Client devices also differ in transmit power, antenna design, receive sensitivity, and roaming behavior. Post-deployment validation measures the actual environment and confirms whether the WLAN meets the original design requirements. Prediction and validation therefore complement one another rather than compete.

Question 260.

Users report good RSSI and SNR, but throughput drops sharply whenever several neighboring APs are active on the same channel. What should be investigated first?

1. DHCP lease duration
   2. SSID spelling
   3. RADIUS certificate expiration only
   4. Co-channel contention and channel reuse**

Correct Answer: 4. Co-channel contention and channel reuse

Explanation:

Strong RSSI and good SNR indicate that the desired signal is usable, but they do not reveal how much airtime is available. If performance drops when neighboring same-channel APs become active, co-channel contention is a likely cause. Devices that can hear one another on the same channel must share airtime through CSMA/CA, reducing effective throughput. The administrator should examine channel utilization, cell overlap, transmit power, channel width, client density, and channel reuse. DHCP, SSID naming, and certificate expiration would not normally correlate directly with same-channel AP activity.