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HCIP-WLAN practice questions

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Question 1WLAN Fundamentals and Standards (802.11 PHY/MAC, RF basics, WLAN architecture)

In an 802.11ac VHT frame, which field of the PLCP header indicates whether the payload uses BCC or LDPC forward error correction?

  1. The SERVICE field of the Data field
  2. The Frame Control field of the MAC header
  3. The Length subfield of L-SIG
  4. The SU/MU coding field inside VHT-SIG-A Correct answer.

Explanation

VHT-SIG-A carries a Coding bit that tells the receiver whether the VHT data portion is encoded with binary convolutional coding or low-density parity-check coding. The MAC header and the legacy L-SIG are decoded before VHT-specific parameters are known and carry no such indication. The SERVICE field is part of the data scrambler initialization, not the coding choice.

Question 2WLAN Fundamentals and Standards (802.11 PHY/MAC, RF basics, WLAN architecture)

A client and AP are 30 m apart in an open office with a clear line of sight at 5 GHz. Which propagation effect most directly explains why the received signal is weaker than the free-space path loss model predicts?

  1. Polarization mismatch from the omnidirectional antennas
  2. Fresnel-zone obstruction by the ceiling and furniture Correct answer.
  3. Doppler shift caused by stationary desks
  4. Frequency hopping across the 5 GHz band

Explanation

Real environments rarely provide a perfect first Fresnel zone; partial obstruction by ceilings, partitions, and furniture adds diffraction loss beyond pure free-space spreading. Doppler shift requires motion and is negligible for fixed desks. Antenna polarization and channel access method do not explain excess path loss in this scenario.

Question 3WLAN Fundamentals and Standards (802.11 PHY/MAC, RF basics, WLAN architecture)

Which 802.11 MAC mechanism requires a station to sense the medium idle for a DIFS interval plus a random backoff before transmitting a data frame?

  1. Point Coordination Function polling
  2. Distributed Coordination Function contention Correct answer.
  3. Block acknowledgment agreement
  4. Target wake time negotiation

Explanation

DCF is the mandatory contention-based access method: a station defers for DIFS, then counts down a random backoff slot counter while the medium stays idle. PCF is an optional centralized polling method, while block acknowledgment and target wake time are efficiency features layered on top of frame exchange rather than medium-access arbitration.

Question 4WLAN Fundamentals and Standards (802.11 PHY/MAC, RF basics, WLAN architecture)

An engineer must support 80 MHz channel bonding in the 5 GHz band while keeping at least one 20 MHz channel free for legacy clients. Which channel arrangement satisfies this requirement in the common UNII-1/UNII-3 planning model?

  1. Bond channels 36 and 40 only and reserve 44 and 48
  2. Bond channels 149 and 153 and reserve 157
  3. Bond channels 52, 56, 60, and 64 and reserve 100
  4. Bond channels 36, 40, 44, and 48 into one 80 MHz segment Correct answer.

Explanation

An 80 MHz channel in UNII-1 is formed from the contiguous 20 MHz channels 36, 40, 44, and 48, leaving UNII-3 channels such as 149-161 available for legacy 20 MHz use. Bonding only two channels yields 40 MHz, not 80 MHz. Reserving a channel inside a different band segment does not preserve a 20 MHz channel adjacent to the bonded segment in the way the plan requires.

Question 5WLAN Fundamentals and Standards (802.11 PHY/MAC, RF basics, WLAN architecture)

Which statement correctly describes the difference between an autonomous AP architecture and a fit AP architecture using a CAPWAP-based AC?

  1. Fit APs perform all RF management locally, while autonomous APs rely on a central controller for channel assignment
  2. Autonomous APs hold the full configuration and forwarding logic locally, while fit APs depend on the AC for configuration and often for tunneled forwarding Correct answer.
  3. Fit APs use only Layer 2 switching, while autonomous APs always use Layer 3 routing
  4. Autonomous APs require CAPWAP control tunnels, while fit APs forward all traffic locally without an AC

Explanation

In a fit architecture the access controller supplies configuration, RF management, and optionally the data path through CAPWAP tunnels, whereas an autonomous AP is a self-contained device with local configuration and bridging. The other options invert these roles or misstate the forwarding and management split.

Question 6WLAN Fundamentals and Standards (802.11 PHY/MAC, RF basics, WLAN architecture)

A station transmits a 1500-byte frame at 300 Mbps over a link with negligible propagation delay. Ignoring contention and preamble, roughly how long does the frame occupy the medium?

  1. About 400 microseconds
  2. About 4 microseconds
  3. About 5 milliseconds
  4. About 40 microseconds Correct answer.

Explanation

Air time equals frame size in bits divided by PHY rate: 1500 bytes is 12,000 bits, and 12,000 divided by 300 Mbps is 40 microseconds. The other values misplace the decimal or confuse milliseconds with microseconds. Real air time is longer once preamble, headers, and acknowledgment are added.

Question 7WLAN Fundamentals and Standards (802.11 PHY/MAC, RF basics, WLAN architecture)

Which 802.11 amendment introduced the 6 GHz operation, multi-resource-unit signaling, and the trigger-based uplink OFDMA design marketed as Wi-Fi 6E?

  1. 802.11n
  2. 802.11ad
  3. 802.11ac
  4. 802.11ax Correct answer.

Explanation

802.11ax (Wi-Fi 6) added OFDMA, trigger-based uplink, and later the 6 GHz extension known as Wi-Fi 6E. 802.11ac is 5 GHz only with OFDM and MU-MIMO downlink, 802.11n is 2.4/5 GHz HT, and 802.11ad is 60 GHz DMG.

Question 8WLAN Fundamentals and Standards (802.11 PHY/MAC, RF basics, WLAN architecture)

A WLAN design requires 40 MHz channels in the 2.4 GHz band. What is the primary practical consequence?

  1. The band gains additional non-overlapping channels because bonding doubles the spectrum
  2. The AP must disable OFDM and use DSSS to support the wider channel
  3. Legacy 802.11b clients gain throughput because they can use both bonded halves
  4. Only one 40 MHz channel fits without overlapping, so co-channel interference risk rises sharply Correct answer.

Explanation

The 2.4 GHz band offers only three non-overlapping 20 MHz channels (1, 6, 11 in North America), so a 40 MHz bond consumes two of them and leaves little room for reuse, increasing co-channel interference. Bonding does not create new spectrum, legacy DSSS clients cannot exploit 40 MHz HT channels, and OFDM remains the modulation.

Question 9WLAN Fundamentals and Standards (802.11 PHY/MAC, RF basics, WLAN architecture)

Which field in the 802.11 MAC header is used by a receiving station to filter duplicate retransmitted frames?

  1. The Frame Check Sequence
  2. The Sequence Control field Correct answer.
  3. The Duration/ID field
  4. The Capability Information field

Explanation

Sequence Control carries a 12-bit sequence number and a fragment number that let a receiver detect and discard duplicates caused by retransmission. Duration/ID reserves the medium, the FCS detects bit errors, and Capability Information advertises features in management frames.

Question 10WLAN Fundamentals and Standards (802.11 PHY/MAC, RF basics, WLAN architecture)

A network uses a single AC managing 40 fit APs across two buildings connected by a Layer 3 routed core. Which CAPWAP deployment mode is required to keep AP-to-AC traffic working across the routed boundary?

  1. CAPWAP in Layer 3 mode with APs discovering the AC by IP address Correct answer.
  2. CAPWAP in monitor mode with the AC in sniffer mode
  3. CAPWAP in Layer 2 mode with APs discovering the AC by broadcast
  4. CAPWAP in split-MAC mode with local forwarding only

Explanation

When APs and the AC sit in different IP subnets, CAPWAP must operate in Layer 3 mode, where APs locate the AC by configured or DHCP-provided IP addresses and the tunnel crosses routers. Layer 2 discovery relies on broadcast within one subnet, and local forwarding or monitor mode do not address AC reachability across a routed core.

Question 11WLAN Fundamentals and Standards (802.11 PHY/MAC, RF basics, WLAN architecture)

Which statement best describes the role of the 802.11 RTS/CTS exchange in mitigating the hidden node problem?

  1. The CTS frame is sent by the AP only after it receives the acknowledgment
  2. The RTS/CTS exchange replaces the need for a random backoff
  3. The CTS frame heard by nearby stations sets their NAV, so they defer while the sender transmits Correct answer.
  4. The RTS frame carries the full data payload, reducing the need for CTS

Explanation

A station that cannot hear the sender but hears the AP's CTS will set its NAV from the Duration field and stay silent, preventing a collision at the AP. RTS carries no payload, CTS precedes the data transmission, and backoff is still performed before the RTS.

Question 12WLAN Fundamentals and Standards (802.11 PHY/MAC, RF basics, WLAN architecture)

Which modulation and coding scheme in 802.11ac provides 256-QAM with a 5/6 code rate?

  1. MCS 7
  2. MCS 5
  3. MCS 0
  4. MCS 9 Correct answer.

Explanation

In 802.11ac, MCS 9 pairs 256-QAM with a 5/6 coding rate and is the highest mandatory-index scheme for a single spatial stream. MCS 7 uses 64-QAM 5/6, MCS 5 uses 64-QAM 2/3, and MCS 0 uses BPSK 1/2.

Question 13WLAN Fundamentals and Standards (802.11 PHY/MAC, RF basics, WLAN architecture)

An AP radio transmits at 20 dBm and feeds an antenna with 5 dBi gain through a cable with 2 dB loss. What is the approximate EIRP?

  1. 27 dBm
  2. 23 dBm Correct answer.
  3. 17 dBm
  4. 25 dBm

Explanation

EIRP in dBm equals transmit power plus antenna gain minus cable loss: 20 + 5 - 2 = 23 dBm. Adding gain without subtracting cable loss gives 25 dBm, and the other values misapply the signs of the cable and antenna terms.

Question 14WLAN Fundamentals and Standards (802.11 PHY/MAC, RF basics, WLAN architecture)

Which 802.11 feature allows an AP to transmit to multiple stations simultaneously in the downlink using separate spatial streams?

  1. Beamforming feedback compression
  2. Downlink MU-MIMO Correct answer.
  3. Uplink OFDMA
  4. Spatial multiplexing with a single client

Explanation

Downlink MU-MIMO lets an AP form separate beams to several clients in the same channel at once, each receiving its own spatial stream(s). Uplink OFDMA shares subcarriers rather than spatial streams, single-client spatial multiplexing serves one client, and beamforming feedback compression is a sounding mechanism, not a multi-user transmission mode.

Question 15WLAN Fundamentals and Standards (802.11 PHY/MAC, RF basics, WLAN architecture)

A WLAN must serve a dense lecture hall where many clients send small uplink packets. Which 802.11ax feature most directly reduces per-client contention overhead in this scenario?

  1. Trigger-based uplink OFDMA with multi-user acknowledgments Correct answer.
  2. Downlink MU-MIMO with four spatial streams
  3. 256-QAM with a 5/6 code rate
  4. 80+80 MHz channel bonding

Explanation

Trigger frames schedule multiple clients to transmit uplink resource units in the same PPDU, and multi-user acknowledgments confirm them together, cutting contention and preamble overhead for many small packets. Wider channels, MU-MIMO, and higher-order modulation raise per-link throughput but do not reduce contention overhead for small uplink frames.

Question 16WLAN Fundamentals and Standards (802.11 PHY/MAC, RF basics, WLAN architecture)

Which frame type does an AP use to announce its SSID, supported rates, and channel information to stations in its coverage area?

  1. Beacon management frame Correct answer.
  2. Association request management frame
  3. Authentication management frame
  4. Probe request management frame

Explanation

Beacons are periodic management frames broadcast by the AP that advertise the SSID, supported rates, channel, and capability information. Probe requests come from clients seeking networks, association requests come from clients joining, and authentication frames handle the authentication exchange.

Question 17WLAN Fundamentals and Standards (802.11 PHY/MAC, RF basics, WLAN architecture)

An engineer observes that a station's data rate drops from 300 Mbps to 65 Mbps as it moves away from the AP. Which mechanism explains this behavior?

  1. Channel bonding automatically increasing from 20 to 40 MHz
  2. Rate adaptation selecting a more robust MCS as SNR and RSSI degrade Correct answer.
  3. The AC reassigning the station to a different SSID
  4. The station switching from OFDM to DSSS to improve range

Explanation

Rate adaptation algorithms lower the MCS index, using more robust modulation and coding, when link quality falls, trading throughput for reliability. Bonding would widen the channel rather than lower the rate, SSID reassignment is a roaming or policy action, and modern 802.11 uses OFDM rather than DSSS for these rates.

Question 18WLAN Fundamentals and Standards (802.11 PHY/MAC, RF basics, WLAN architecture)

Which statement correctly describes the relationship between RSSI and SNR for a client at a fixed distance from an AP?

  1. RSSI and SNR are identical measurements expressed in different units
  2. SNR is fixed by distance, while RSSI varies only with the antenna type
  3. RSSI measures noise and SNR measures signal strength
  4. RSSI indicates received signal strength, while SNR compares that signal to the noise floor and can change if interference rises Correct answer.

Explanation

RSSI quantifies the received signal power, whereas SNR is the ratio of signal power to noise power, so added interference or a higher noise floor lowers SNR even when RSSI is unchanged. The two are related but distinct, and neither is a pure function of antenna type alone.

Question 19WLAN Fundamentals and Standards (802.11 PHY/MAC, RF basics, WLAN architecture)

Which 802.11 amendment first standardized operation in the 60 GHz band for very high throughput short-range links?

  1. 802.11ah
  2. 802.11ad Correct answer.
  3. 802.11ax
  4. 802.11af

Explanation

802.11ad defines the DMG PHY and MAC for 60 GHz operation with multi-gigabit rates over short distances. 802.11ah covers sub-1 GHz long-range IoT, 802.11af covers TV white space, and 802.11ax is the 2.4/5/6 GHz high-efficiency amendment.

Question 20WLAN Fundamentals and Standards (802.11 PHY/MAC, RF basics, WLAN architecture)

A wireless bridge must carry traffic between two buildings 3 km apart with clear line of sight. Which design consideration is most important for link reliability?

  1. Ensuring sufficient Fresnel zone clearance above the terrain and rooftops Correct answer.
  2. Using the widest possible channel to reduce air time
  3. Disabling encryption to reduce frame overhead
  4. Maximizing the number of SSIDs broadcast by the bridge

Explanation

At long range the first Fresnel zone can be tens of meters wide; obstructions inside it cause diffraction loss that can break the link even with optical line of sight. SSID count, channel width, and encryption affect capacity or overhead but not the fundamental propagation margin.

Question 21WLAN Fundamentals and Standards (802.11 PHY/MAC, RF basics, WLAN architecture)

Which mechanism allows an 802.11 station to save power by sleeping and waking to receive beacon frames that indicate buffered traffic?

  1. Block acknowledgment with a compressed bitmap
  2. Frame aggregation using A-MPDU
  3. Power Save mode with the TIM and DTIM elements in beacons Correct answer.
  4. Dynamic frequency selection

Explanation

A station in Power Save mode sleeps between beacon intervals; the Traffic Indication Map in beacons flags buffered unicast traffic, and the Delivery TIM marks multicast/broadcast delivery. Block acknowledgment, A-MPDU, and DFS affect efficiency or radar avoidance rather than sleep scheduling.

Question 22WLAN Fundamentals and Standards (802.11 PHY/MAC, RF basics, WLAN architecture)

Which statement about the 802.11 MAC address fields in a frame sent from a wireless client to a server behind a wired router is correct?

  1. Address 1 is the broadcast address, Address 2 is the client, and Address 3 is the AP
  2. Address 1 is the router, Address 2 is the server, and Address 3 is the client
  3. Address 1 is the client, Address 2 is the AP, and Address 3 is the server
  4. Address 1 is the AP's BSSID, Address 2 is the client, and Address 3 is the router's MAC Correct answer.

Explanation

In an infrastructure BSS, a client-to-DS frame sets Address 1 to the receiving AP (BSSID), Address 2 to the transmitting client, and Address 3 to the destination MAC beyond the DS, here the router. The other options swap transmitter and receiver roles or misuse the broadcast address.

Question 23WLAN Fundamentals and Standards (802.11 PHY/MAC, RF basics, WLAN architecture)

What is the primary purpose of the 802.11 association procedure after a client has authenticated?

  1. To reserve a dedicated resource unit for the client
  2. To create the association and negotiate capabilities such as supported rates and QoS before data exchange Correct answer.
  3. To assign the client an IP address through DHCP
  4. To verify the client's identity against a RADIUS server

Explanation

Association binds the client to a specific AP's BSS and exchanges capability information such as supported rates, HT/VHT elements, and QoS so both sides agree on operating parameters. Identity verification belongs to authentication (often 802.1X), IP assignment is DHCP at Layer 3, and RU scheduling is dynamic per transmission.

Question 24WLAN Fundamentals and Standards (802.11 PHY/MAC, RF basics, WLAN architecture)

An AP in a warehouse reports strong RSSI from clients but poor throughput and high retry counts. Which explanation is most consistent with these observations?

  1. High noise or co-channel interference is lowering SNR despite adequate signal strength Correct answer.
  2. The clients are too close to the AP and overloading the receiver front end
  3. The clients are negotiating 802.11b rates, which always lowers retries
  4. The AP is using too narrow a channel, reducing capacity

Explanation

Retries rise when frames are corrupted, which depends on SNR rather than RSSI alone; strong signal with a high noise floor from interferers or co-channel APs produces exactly this pattern. Proximity overload is uncommon and would show as receiver saturation, narrower channels reduce capacity but not retry rate directly, and low 802.11b rates do not inherently reduce retries.

Question 25WLAN Networking and CAPWAP Principles (AP-AC architecture, CAPWAP tunnel establishment, AP onboarding)

In a Huawei WLAN architecture, which device terminates the CAPWAP tunnels and manages the access points centrally?

  1. The PoE switch
  2. The RADIUS server
  3. The access point (AP)
  4. The access controller (AC) Correct answer.

Explanation

The AC is the centralized control device: it terminates CAPWAP control and data tunnels, pushes configuration to APs, and handles roaming and admission decisions. APs are the managed endpoints, while switches and RADIUS servers provide transport and authentication services only.

Question 26WLAN Networking and CAPWAP Principles (AP-AC architecture, CAPWAP tunnel establishment, AP onboarding)

Which two message types are exchanged over the CAPWAP control channel between an AP and an AC?

  1. DHCP Discover and DHCP Offer
  2. ARP Request and ARP Reply
  3. Discovery and Join Correct answer.
  4. EAPOL-Start and EAPOL-Logoff

Explanation

CAPWAP defines a control channel that carries Discovery Request/Response and Join Request/Response during tunnel setup, followed by configuration and keepalive messages. The other pairs belong to link authentication, address assignment, or address resolution, not to CAPWAP control.

Question 27WLAN Networking and CAPWAP Principles (AP-AC architecture, CAPWAP tunnel establishment, AP onboarding)

An AP has no preconfigured AC address and no DHCP option carrying AC information. How does the AP normally begin locating an AC?

  1. It sends a CAPWAP Discovery Request to the limited broadcast address Correct answer.
  2. It waits for the AC to dial into the AP
  3. It uses the default gateway as the AC
  4. It queries the RADIUS server for the AC address

Explanation

Without a statically configured or DHCP-provided AC list, the AP falls back to Layer 3 broadcast discovery, sending a Discovery Request to 255.255.255.255. Any reachable AC can answer with a Discovery Response listing its capabilities.

Question 28WLAN Networking and CAPWAP Principles (AP-AC architecture, CAPWAP tunnel establishment, AP onboarding)

What is the primary purpose of the CAPWAP data channel between an AP and an AC in tunnel forwarding mode?

  1. To synchronize the AC and AP clocks
  2. To exchange routing protocol updates
  3. To carry encapsulated client data frames between the AP and the AC Correct answer.
  4. To distribute PoE power budgets

Explanation

In tunnel forwarding mode, client traffic is encapsulated and sent over the CAPWAP data channel to the AC, which then forwards it into the wired network. The control channel is separate and handles management traffic only.

Question 29WLAN Networking and CAPWAP Principles (AP-AC architecture, CAPWAP tunnel establishment, AP onboarding)

Which transport protocol and port does CAPWAP use for its control channel by default?

  1. UDP port 5246 Correct answer.
  2. TCP port 443
  3. TCP port 5246
  4. UDP port 5247

Explanation

CAPWAP control messages are carried over UDP with destination port 5246, while the data channel uses UDP port 5247. TCP is not used for CAPWAP tunnels.

Question 30WLAN Networking and CAPWAP Principles (AP-AC architecture, CAPWAP tunnel establishment, AP onboarding)

After an AP receives Discovery Responses from several ACs, what does it send to the AC it has selected?

  1. An Association Request
  2. A Join Request Correct answer.
  3. A DHCP Request
  4. A Discovery Request

Explanation

Once the AP chooses an AC, it sends a Join Request over the control channel to establish the CAPWAP session, and the AC replies with a Join Response. Discovery Requests are used earlier, during the search phase.

Question 31WLAN Networking and CAPWAP Principles (AP-AC architecture, CAPWAP tunnel establishment, AP onboarding)

Which statement describes the AP state in which it has an established CAPWAP session and is actively serving clients under AC control?

  1. Idle state
  2. Discovery state
  3. Sulphur state
  4. Run state Correct answer.

Explanation

After a successful Join and configuration exchange, the AP enters the Run state, where it receives configuration, reports status, and forwards client traffic. Discovery is the earlier search phase and Idle is a pre-join condition.

Question 32WLAN Networking and CAPWAP Principles (AP-AC architecture, CAPWAP tunnel establishment, AP onboarding)

Which addressing mode allows an AP to obtain its IP address and AC address information from a DHCP server before starting CAPWAP discovery?

  1. Static NAT translation
  2. Proxy ARP
  3. PPPoE dial-up
  4. DHCP with vendor-specific option 43 Correct answer.

Explanation

DHCP option 43 can carry AC IP addresses to the AP, letting it unicast Discovery Requests directly instead of broadcasting. Static NAT, PPPoE, and proxy ARP do not deliver AC address information.

Question 33WLAN Networking and CAPWAP Principles (AP-AC architecture, CAPWAP tunnel establishment, AP onboarding)

An AP is on subnet 10.1.1.0/24 and the AC is on 10.2.2.0/24 with a routed path between them. Which discovery method must succeed for the AP to find the AC without any prior configuration?

  1. Layer 2 broadcast confined to the AP subnet
  2. Layer 3 unicast or broadcast discovery reaching the AC through routing Correct answer.
  3. Link Layer Discovery Protocol neighbor advertisement
  4. Spanning Tree BPDU exchange

Explanation

Because the AC is off-subnet, the AP needs Layer 3 discovery: either a broadcast that the network forwards to the AC subnet or a unicast Discovery Request using an AC address learned from DHCP or static configuration. Pure Layer 2 broadcast stays within the local subnet.

Question 34WLAN Networking and CAPWAP Principles (AP-AC architecture, CAPWAP tunnel establishment, AP onboarding)

An AP completes discovery and joins an AC, but client traffic must remain on the local VLAN at the branch. Which forwarding mode should be configured?

  1. Local forwarding Correct answer.
  2. Tunnel forwarding
  3. Soft-GRE forwarding
  4. Split-MAC bridging

Explanation

Local forwarding keeps client data on the AP's local wired interface while management traffic still traverses the CAPWAP control channel to the AC. Tunnel forwarding instead sends client frames to the AC over the data channel.

Question 35WLAN Networking and CAPWAP Principles (AP-AC architecture, CAPWAP tunnel establishment, AP onboarding)

Which field in the CAPWAP Discovery Request lets an AC decide whether it is a suitable match for the AP?

  1. The AP's DNS server address
  2. The AP's PoE power class
  3. The AP's requested wireless mode and hardware/software version information Correct answer.
  4. The AP's spanning-tree priority

Explanation

The Discovery Request carries AP information such as model, software version, and requested mode, which the AC compares against its own capabilities and configuration before replying. PoE class, STP priority, and DNS settings are not CAPWAP matching criteria.

Question 36WLAN Networking and CAPWAP Principles (AP-AC architecture, CAPWAP tunnel establishment, AP onboarding)

What is the role of CAPWAP control keepalive (Echo) messages after the session is established?

  1. They detect a lost AC or AP so the tunnel can be torn down and re-established Correct answer.
  2. They assign VLANs to client traffic
  3. They encrypt client payloads
  4. They synchronize the AP radio channels

Explanation

Echo Request/Response messages act as heartbeats; if replies stop, the peer is considered unreachable and the CAPWAP session is reset. Encryption, VLAN assignment, and radio channel planning use other mechanisms.

Question 37WLAN Networking and CAPWAP Principles (AP-AC architecture, CAPWAP tunnel establishment, AP onboarding)

An AP repeatedly fails at the Join stage even though Discovery Responses arrive. Which condition most directly explains this?

  1. The AC rejects the AP because it has reached its licensed AP capacity or the AP image is incompatible Correct answer.
  2. The AP's radio is set to monitor mode
  3. The AP cannot obtain PoE power
  4. The client station failed 802.11 association

Explanation

A Join Response can carry a failure result when the AC has no capacity, the AP model or software is unsupported, or authentication of the join fails. PoE, client association, and radio mode do not govern the CAPWAP Join exchange.

Question 38WLAN Networking and CAPWAP Principles (AP-AC architecture, CAPWAP tunnel establishment, AP onboarding)

Which statement about CAPWAP tunnel endpoints is correct?

  1. The tunnel terminates on the PoE switch
  2. The AP and AC each use their own IP addresses as tunnel endpoints, and the tunnel can cross a routed network Correct answer.
  3. The tunnel uses the client's IP address as its endpoint
  4. The tunnel requires the AP and AC to be in the same Layer 2 broadcast domain

Explanation

CAPWAP is an IP-based tunneling protocol, so the AP and AC encapsulate traffic using their own routable IP addresses and the tunnel can traverse Layer 3 networks. There is no requirement for a shared broadcast domain.

Question 39WLAN Networking and CAPWAP Principles (AP-AC architecture, CAPWAP tunnel establishment, AP onboarding)

In a Huawei AC deployment, which interface typically sources the CAPWAP tunnel and hosts the AP management IP addressing?

  1. The AC's HA heartbeat port only
  2. The AC's CAPWAP source interface, commonly a VLAN interface Correct answer.
  3. The AC's USB port
  4. The AC's console port

Explanation

The AC uses a configured source interface, usually a VLAN interface with an IP address reachable by the APs, as the local endpoint for CAPWAP tunnels. Console and USB ports are for local management, and the HA port is dedicated to redundancy.

Question 40WLAN Networking and CAPWAP Principles (AP-AC architecture, CAPWAP tunnel establishment, AP onboarding)

An AP boots and receives a DHCP address but no AC address. It broadcasts a Discovery Request, yet no AC replies. Which is the most likely cause?

  1. The AC is reachable but the broadcast is not forwarded to the AC's subnet and no DHCP option 43 or static AC address is configured Correct answer.
  2. The AP radio is disabled
  3. The client uses WPA2-PSK
  4. The SSID is hidden

Explanation

If the AC sits on a different subnet and broadcast forwarding or DHCP option 43 is missing, the Discovery Request never reaches it. Radio, SSID, and client security settings do not affect the AP's ability to discover an AC.

Question 41WLAN Networking and CAPWAP Principles (AP-AC architecture, CAPWAP tunnel establishment, AP onboarding)

Which sequence correctly orders the main phases of AP onboarding with CAPWAP?

  1. Download configuration, discover AC, obtain IP address, join AC
  2. Join AC, obtain IP address, discover AC, enter Run state
  3. Obtain IP address, discover AC, join AC, download configuration, enter Run state Correct answer.
  4. Discover AC, enter Run state, join AC, obtain IP address

Explanation

The AP first needs IP connectivity, then discovers candidate ACs, joins the chosen AC, receives its configuration, and finally enters the Run state to serve clients. Joining before addressing or configuring is not possible.

Question 42WLAN Networking and CAPWAP Principles (AP-AC architecture, CAPWAP tunnel establishment, AP onboarding)

Which mechanism lets an AP authenticate to the AC during CAPWAP session establishment so that unauthorized APs are rejected?

  1. CAPWAP DTLS with certificate or pre-shared-key based authentication Correct answer.
  2. IGMP snooping
  3. WPA2-PSK four-way handshake
  4. DHCP snooping

Explanation

CAPWAP can protect the control channel with DTLS, and the join exchange can authenticate the AP using certificates or pre-shared keys so the AC accepts only authorized devices. WPA2-PSK, DHCP snooping, and IGMP snooping serve different purposes.

Question 43WLAN Networking and CAPWAP Principles (AP-AC architecture, CAPWAP tunnel establishment, AP onboarding)

An AP is configured with a static AC address list containing 10.0.0.5, but the AC has moved to 10.0.0.9. The AP still boots and joins successfully. Which behavior explains this?

  1. The AP uses the default gateway as a backup AC
  2. The AP falls back to broadcast or DHCP-based discovery when the configured AC does not answer Correct answer.
  3. The old AC forwards the Join to the new AC
  4. The AP automatically learns the new address from ARP and joins

Explanation

Static AC addresses are tried first, but if no response arrives the AP continues with other discovery methods such as broadcast or DHCP option 43. It does not learn AC addresses from ARP or via forwarding by the old AC.

Question 44WLAN Networking and CAPWAP Principles (AP-AC architecture, CAPWAP tunnel establishment, AP onboarding)

Which statement best distinguishes the CAPWAP control channel from the data channel?

  1. Both channels carry client traffic and differ only in encryption
  2. The control channel uses TCP while the data channel uses UDP
  3. The data channel exists only before the AP joins the AC
  4. The control channel carries management and state messages over UDP 5246, while the data channel carries encapsulated client traffic over UDP 5247 Correct answer.

Explanation

CAPWAP separates signaling from payload: control messages such as Discovery, Join, and configuration use UDP 5246, while client frames are encapsulated on the data channel using UDP 5247. Neither channel uses TCP, and the data channel is used after the session is established.

Question 45WLAN Networking and CAPWAP Principles (AP-AC architecture, CAPWAP tunnel establishment, AP onboarding)

An AC is configured to authenticate APs by serial number, but a replacement AP with a new serial number is installed. What is the expected result at the Join stage?

  1. The AP bypasses CAPWAP and forwards traffic locally
  2. The AP joins and inherits the old AP's configuration automatically
  3. The AP converts to a standalone device without AC management
  4. The AC rejects the Join because the AP is not in the permitted list Correct answer.

Explanation

When AP authentication is enforced by serial number or MAC, an unknown AP fails the Join and cannot enter Run state. It must be added to the AC's permitted AP list before it can be managed.

Question 46WLAN Networking and CAPWAP Principles (AP-AC architecture, CAPWAP tunnel establishment, AP onboarding)

A network engineer observes that client traffic from a branch AP traverses the WAN to the AC before reaching the Internet. Which change reduces WAN load while preserving centralized management?

  1. Enable tunnel forwarding on all SSIDs
  2. Move the AC to the branch and remove all APs from management
  3. Switch the WLAN to local forwarding so client data egresses at the AP Correct answer.
  4. Disable the CAPWAP control channel

Explanation

Local forwarding keeps the control channel to the AC for management while bridging client data onto the local wired network, removing the WAN hairpin. Disabling control or enabling more tunneling would worsen the problem or break management.

Question 47WLAN Networking and CAPWAP Principles (AP-AC architecture, CAPWAP tunnel establishment, AP onboarding)

Two ACs are deployed for redundancy with the same AP management network. Which design ensures an AP can still onboard if its primary AC fails during the Join phase?

  1. Rely on the AP to keep its half-open CAPWAP session indefinitely
  2. Disable CAPWAP keepalives so the failure is not detected
  3. Configure the AP to receive multiple AC addresses so it can retry discovery and join the standby AC Correct answer.
  4. Configure the AP to use the failed AC's MAC address as its own

Explanation

Providing multiple candidate AC addresses through DHCP option 43 or a static list lets the AP re-run discovery and join an alternate AC after a failure. A half-open session cannot survive, and suppressing keepalives only delays recovery.

Question 48WLAN Networking and CAPWAP Principles (AP-AC architecture, CAPWAP tunnel establishment, AP onboarding)

An AP and AC are separated by a firewall. CAPWAP Discovery succeeds but the Join fails and no configuration is downloaded. Which firewall change is most likely required?

  1. Permit only TCP 80 to the AC
  2. Permit UDP 67 and 68 only
  3. Permit ICMP redirect messages
  4. Permit inbound UDP 5246 and 5247 to the AC and the corresponding return traffic Correct answer.

Explanation

CAPWAP control uses UDP 5246 and the data channel uses UDP 5247, so both must be allowed toward the AC with return traffic. HTTP, ICMP redirects, and DHCP ports alone do not carry the Join or configuration exchange.

Question 49WLAN Networking and CAPWAP Principles (AP-AC architecture, CAPWAP tunnel establishment, AP onboarding)

An AP shows it has completed discovery and join but remains unable to forward client traffic in tunnel mode. Which condition best explains this?

  1. The AP has no serial number
  2. The CAPWAP data channel is blocked while the control channel is permitted Correct answer.
  3. The AC has no console cable attached
  4. The SSID is configured with WPA2-PSK

Explanation

Control and data channels use different UDP ports, so a policy that permits only 5246 allows discovery, join, and configuration while blocking client payload on 5247. Serial number, console access, and client security do not block the data path in this way.

Question 50WLAN Networking and CAPWAP Principles (AP-AC architecture, CAPWAP tunnel establishment, AP onboarding)

In a Huawei WLAN deployment, which transport protocol carries CAPWAP control messages between an AP and an AC, and which port does it use by default?

  1. UDP, destination port 5246 Correct answer.
  2. UDP, destination port 5247
  3. TCP, destination port 5246
  4. TCP, destination port 5247

Explanation

CAPWAP separates control and data into two channels, and the control channel runs over UDP with destination port 5246. UDP is chosen because the control protocol implements its own reliability and keepalive mechanisms rather than relying on TCP. Port 5247 belongs to the data channel, not the control channel.