Free CWAP-405 practice test: 30 questions with answers

The AP answers an Association Request with an Association Response that carries a status code and the AID for the client. A Probe Response answers active scanning, a Reassociation Response is used when a client moves from another AP, and a Beacon is a periodic broadcast that does not complete a join.

The Current AP Address field lets the new AP reach the previous AP across the distribution system, so client state and buffered frames can be transferred. The other options misdescribe the field: deauthentication is not triggered this way, timing comes from each AP's own beacons, and IP addressing is handled by DHCP rather than by the reassociation frame.

Fast BSS Transition (802.11r) lets the client reuse key material within the mobility domain, so the roam needs a shorter key exchange. 802.11k, 802.11v and 802.11w address neighbor reports, transition suggestions and management frame protection rather than fast key setup.

The Block Ack bitmap reports which MPDUs in the burst were received correctly, so the sender retransmits only the missing ones. Repeating the whole burst, rejoining the BSS or dropping frames silently do not match how Block Ack works, and the bitmap does not describe TXOP length.

A Trigger frame from the AP defines which stations send, on which resource units and when, so that OFDMA uplink responses arrive together. An NDP Announcement starts channel sounding, a Block Ack Request asks for acknowledgment state, and an Action frame with a group identifier does not schedule uplink transmissions.

A-MSDU packs multiple MSDUs into one MPDU that has a single MAC header and FCS. A-MPDU carries multiple complete MPDUs that each have their own header and FCS, Block Ack is an acknowledgment method, and fragmentation splits one MSDU rather than combining several.

Each MSDU or MPDU carries a sequence number, and a retransmitted frame keeps its original sequence number, so the receiver can discard the duplicate. The Duration/ID field reserves airtime, Address 4 appears only in certain WDS frames, and the subtype identifies the frame type rather than duplicates.

The Retry bit marks a retransmission, and retransmissions keep the sequence number of the original frame. Broadcast frames are not acknowledged or retried, reassociation is a separate management exchange, and a new fragment would carry a different fragment number.

A frame that fails the FCS check is not acknowledged, so the sender waits for the ACK timer and retransmits, up to its retry limit. 802.11 has no NAK frame, damaged frames are not passed up the stack, and an ACK for a bad frame would falsely tell the sender that it was received.

An A-MSDU is one MPDU with one FCS, so a failed check invalidates all of its subframes and the sender retransmits the whole unit. Subframes have no separate FCS, the sequence number does not isolate a single subframe, and aggregated frames are not repaired in place.

Monitor mode on a radio tuned to the BSS channel receives 802.11 management and data frames exchanged between other stations and the AP. Managed mode passes only frames for the adapter's own address, and wired captures never carry 802.11 management frames or EAPOL exchanges, which stop at the AP.

A radio receives on one channel at a time, so a capture on one channel cannot see frames sent on other channels. Monitor mode does not supply decryption keys, so encrypted data stays unreadable without them, and an adapter does not select traffic by SSID.

Two capture points, each tuned to one channel, record every frame on both channels, and synchronized timestamps let the traces be aligned. Hopping one radio misses frames while it is away, a 20 MHz setting does not let a single radio cover two separate channels, and a wired capture never contains the other AP's wireless frames.

Decryption needs the passphrase (with the SSID) to derive the PMK, and the captured four-way handshake to derive the session keys. Beacon fields are not secrets, and a RADIUS shared secret belongs to 802.1X networks, while WPA2-Personal has no RADIUS server.

Synchronized timestamps let frames from two different capture points be placed on one timeline. Radiotap header versions, MTU settings and matching MAC addresses do not establish timing between separate captures.

Microwave ovens emit broadband interference in the 2.4 GHz band that is tied to the appliance's on-time, which matches the spectrum pattern. A neighboring AP would appear as decodable 802.11 frames, Bluetooth hops are not tied to a kitchen appliance, and deauthentication frames are protocol traffic that a spectrum view cannot show.

A central system combines measurements from many sensors, so interference sources can be compared across the whole site. Decoding client traffic for billing, replacing the channel plan and centralizing frame buffering are not the purpose of spectrum analysis, which looks at RF energy rather than client data.

A waterfall (spectrogram) view adds time as a dimension, so periodic interference appears as repeating patterns. A single snapshot shows one instant, a frame-type pie chart is a protocol statistic rather than an RF view, and a decoded SSID table cannot show non-802.11 energy.

Frequency hopping spreads a device's short bursts across the band, and Bluetooth is a common hopping device in 2.4 GHz. A microwave oven produces a broadband signal tied to its on-time, while a fixed-channel camera or access point does not change frequency in this way.

Channel utilization on a spectrum view reflects energy and busy time, so non-802.11 sources can make a channel look busy while few decodable frames appear. Utilization is not calculated only from decoded frames, power save reduces transmissions rather than raising utilization, and Probe Requests come from clients rather than APs.

L-SIG sits in the legacy preamble and is sent in a format that non-HT stations can decode, so they can compute the PPDU duration and defer. HT-SIG and VHT-SIG-A are read only by newer stations, and the training fields serve receiver timing rather than telling a legacy station how long to defer.

Pseudo-headers are added by the capture tool, not sent over the air, and they describe the radio conditions under which the frame was received. Keys, MAC header replacement and FCS values are not the job of a pseudo-header, and the FCS stays part of the 802.11 frame itself.

Decoding a PPDU requires an adapter that understands its PHY format, and an 802.11g-only radio cannot decode the VHT transmissions of an 802.11ac network. The other options describe partial or incorrect capture behaviour, such as losing only management frames or switching to a band the 5 GHz network does not use.

The PSDU is the payload portion of a PPDU and carries the MPDU or A-MPDU that holds the MAC frame. The training fields, SIG fields and preamble are PHY-layer overhead that synchronize the receiver or describe the transmission rather than carry the MAC frame.

The short preamble is shorter than the long one, so it takes less airtime and leaves more of each DSSS transmission for payload. It does not add transmit power or change how 802.11a stations work, and it never removes the FCS, which stays in every MAC frame.

DCF uses binary exponential backoff, so the contention window doubles after each failed attempt until it reaches its maximum, which reduces repeated collisions. Halving or keeping the window at its minimum would increase collisions, and DCF does not use a fixed slot count.

Under default EDCA values, AC_VO has the smallest contention window, so voice wins contention most often. AC_VI, AC_BE and AC_BK receive progressively longer waits and suit video, best-effort and background traffic.

Virtual carrier sense uses the Duration values in overheard frames, including CTS frames from an RTS/CTS exchange, to set the NAV and defer. Physical carrier sense only detects energy the station can hear, which does not help with hidden stations, and the retry counter has nothing to do with deferral.

An ACK follows a unicast frame after a SIFS, the shortest interframe space, so the response goes out before other stations can contend. PIFS is not reserved for beacons, DIFS is the wait before a new contention, and the AC_BK AIFS governs contention rather than ACK spacing.

The exposed node problem occurs when a station defers to a transmission that its own frames would not disrupt, which lowers throughput. The hidden node problem is the reverse, a collision the sender cannot hear, while a NAV overflow and Block Ack retry storms are not the cause described.