Question 1

802.11h (5 GHz with DFS/TPC): number of non-overlapping 20 MHz channels: Considering 802.11h operation in the 5 GHz band (DFS/TPC enabling access to additional UNII bands), approximately how many non-overlapping 20 MHz channels are available?

Accepted Answer

Introduction / Context: 802.11h adds Dynamic Frequency Selection (DFS) and Transmit Power Control (TPC) to 802.11a so that Wi-Fi equipment can legally use more of the 5 GHz spectrum (particularly UNII-2 and UNII-2e) while protecting incumbent radar systems. A common study point is how many non-overlapping 20 MHz channels are available in the 5 GHz band when these extensions are allowed. Given Data / Assumptions: We are discussing 20 MHz channels, not 40/80/160 MHz bonded channels. Regulatory availability varies by country; the question targets the widely cited count enabled by DFS/TPC in many regions. 802.11h is an amendment that broadens usable channels compared to basic 802.11a. Concept / Approach: Classic 802.11a in the U.S. without DFS typically exposes about 12 non-overlapping channels. With 802.11h and DFS/TPC, devices can operate across additional UNII-2 and UNII-2e ranges, raising the practical count to roughly 23 non-overlapping 20 MHz channels (exact sets depend on local regulations and device support). Step-by-Step Solution: Recall baseline (no DFS): about 12 channels.Add DFS/TPC bands (UNII-2/2e): increases available channels substantially.Common exam answer for 802.11h availability: 23 non-overlapping channels. Verification / Alternative check: Consult current regulatory domain tables for your country to confirm exact channels. Enterprise controller GUIs also list enabled 5 GHz channels when DFS is permitted. Why Other Options Are Wrong: 3 is the 2.4 GHz non-overlapping count (802.11b/g in most regions). 12 is typical for basic 802.11a without DFS. 40 greatly exceeds commonly allowed 20 MHz channels in a single regulatory domain. Common Pitfalls: Confusing 2.4 GHz and 5 GHz channel counts; ignoring that DFS availability is regulatory-dependent; mixing 20 MHz counts with bonded-channel (40/80/160 MHz) planning. Final Answer: 23

Question 2

802.11b coverage at the lowest data rate: Approximately what indoor distance can be achieved at the lowest 802.11b data rate under typical conditions?

Accepted Answer

Introduction / Context: 802.11b operates in the 2.4 GHz band and supports data rates down to 1–2 Mbps using robust modulation (DBPSK/DQPSK with Barker coding). At these lowest rates, signals can travel farther indoors than at higher rates, though actual coverage depends heavily on environment and interference. Given Data / Assumptions: Typical indoor office/home environment with walls and furniture. Standard omnidirectional access points and client radios. We seek a commonly cited practical range, not a theoretical maximum. Concept / Approach: As data rates drop, receiver sensitivity thresholds are lower (better), allowing longer distances before frames fail. For 802.11b, industry training materials and vendor datasheets have historically cited about 300 feet (≈90 meters) as a practical indoor range at the lowest rates, with higher rates like 11 Mbps achieving much shorter distances (often around 100–150 feet). Step-by-Step Solution: Recognize lowest-rate advantage: better sensitivity → longer reach.Map to common planning figure: approximately 300 feet indoors.Note that real-world factors (multipath, interference) can reduce or occasionally extend this distance. Verification / Alternative check: AP datasheets list receive sensitivities per rate; site surveys confirm that the cell edge for 1–2 Mbps often lies near 300 feet, varying by construction materials and interference (microwaves, Bluetooth, other APs). Why Other Options Are Wrong: 100 and 175 feet are more typical of higher rates (5.5 or 11 Mbps). 350 feet may occur in open spaces but exceeds the commonly taught planning number for indoor deployments. Common Pitfalls: Assuming outdoor line-of-sight values apply indoors; ignoring regulatory transmit power limits; forgetting that client devices usually limit the uplink due to lower transmit power vs APs. Final Answer: About 300 feet

Question 3

802.11b channel planning: In the 2.4 GHz band, how many non-overlapping 20 MHz channels are available for 802.11b/g in most regulatory domains (e.g., channels 1, 6, and 11 in the U.S.)?

Accepted Answer

Introduction / Context: Channel reuse in the 2.4 GHz band is constrained by the 5 MHz channel center spacing and the 20–22 MHz occupied bandwidth of 802.11b/g channels. Effective frequency planning minimizes adjacent-channel interference by choosing non-overlapping channels. Given Data / Assumptions: Standard 2.4 GHz band allocation with 11 channels in the U.S. (13 in many other regions). Channel width 20–22 MHz; center-to-center spacing 5 MHz. Goal is non-overlapping operation for co-channel reuse. Concept / Approach: Because adjacent channels overlap significantly, only certain channel separations avoid interference. In practice, channels 1, 6, and 11 (U.S.) are spaced far enough apart to provide three non-overlapping 20–22 MHz channels. Other domains may use 1, 5, 9, 13, but the non-overlapping count is still effectively three in most planning guides. Step-by-Step Solution: Recall U.S. channels: 1–11; select 1, 6, 11 for non-overlap.Confirm bandwidth overlap with 5 MHz spacing → adjacent channels collide.Conclude there are three practical non-overlapping channels. Verification / Alternative check: Spectrum analysis in a lab confirms that channels 1, 6, and 11 show minimal spectral overlap. Vendor design guides universally recommend this triad for 2.4 GHz deployments. Why Other Options Are Wrong: 12 and 23 correspond to 5 GHz counts (depending on DFS availability), not 2.4 GHz. 40 is unrelated to any standard 20 MHz non-overlapping count in Wi-Fi. Common Pitfalls: Attempting to use channels like 3, 8, and 11 expecting non-overlap; mixing regulatory domains and assuming additional channels increase the non-overlapping count beyond three for 20 MHz in 2.4 GHz. Final Answer: 3

Question 4

Wi-Fi Fundamentals — IEEE 802.11g Maximum Data Rate In IEEE 802.11 wireless networking, what is the theoretical maximum data rate specified by the 802.11g standard under ideal conditions?

Accepted Answer

Introduction / Context: Wireless LAN standards define nominal data rates under ideal radio conditions. The 802.11g amendment extended earlier 2.4GHz systems by adopting orthogonal frequency division multiplexing (OFDM) while maintaining compatibility with 802.11b. This question checks recall of the headline rate for 802.11g. Given Data / Assumptions: The question is about the standard's theoretical maximum physical layer data rate. Environment is ideal (clear channel, strong signal, no interference). Throughput is different from the PHY rate due to protocol overhead. Concept / Approach: 802.11g uses OFDM in the 2.4GHz band and defines a top PHY rate of 54Mbps. Actual application throughput is typically much lower (often 20–25Mbps single-stream) because management frames, acknowledgments, contention, and modulation fallback reduce effective throughput. Knowing the headline PHY rate helps quickly categorize capabilities across standards (b = 11Mbps, g = 54Mbps, a = 54Mbps at 5GHz, n = higher via MIMO, ac/ax = much higher at 5/6GHz). Step-by-Step Solution: Identify the standard: 802.11g.Recall the top PHY data rate for 802.11g = 54Mbps.Confirm band: operates at 2.4GHz with OFDM (legacy b-compatibility).Select the option that exactly matches 54Mbps. Verification / Alternative check: Compare with related standards: 802.11b tops at 11Mbps (DSSS/CCK); 802.11a is 54Mbps at 5GHz; 802.11n commonly exceeds 100Mbps PHY per stream; therefore, 54Mbps maps uniquely to 802.11g at 2.4GHz (and 802.11a at 5GHz). Why Other Options Are Wrong: 22Mbps: Seen in some proprietary turbo modes; not the 802.11g maximum. 6Mbps: A valid OFDM rate but not the maximum. 11Mbps: That is 802.11b's maximum, not 802.11g's. 72.2Mbps: Common single-stream 802.11n MCS rate, not 802.11g. Common Pitfalls: Confusing PHY rate with real throughput; users often expect 54Mbps usable speed, but protocol overhead and RF conditions reduce it significantly. Final Answer: 54Mbps

Question 5

Cisco Unified Wireless — What does “split-MAC” architecture mean? In Cisco's Unified Wireless Solution, explain the split-MAC architecture and choose the correct description that reflects how 802.11 processing is divided between lightweight access p…

Accepted Answer

Introduction / Context: Enterprise Wi-Fi systems often centralize control to simplify configuration, roaming, and security. Cisco's “split-MAC” architecture underpins lightweight AP (LAP) deployments with a Wireless LAN Controller (WLC), dividing responsibilities for 802.11 tasks to optimize performance and manageability. Given Data / Assumptions: Lightweight APs are joined to a WLC via CAPWAP tunnels. Management and control functions can be centralized. Latency-sensitive RF functions should remain near the air interface. Concept / Approach: In split-MAC, time-critical 802.11 operations (for example, beaconing, probe/association handling, RF measurements) are performed on the AP, while centralized tasks (authentication policy, roaming decisions, QoS enforcement, VLAN mapping) execute on the controller. Frames are encapsulated and transported to the WLC, which applies policy and forwards traffic. This yields simplified management, consistent policy, and faster roaming while keeping radio-timing tasks local to the AP. Step-by-Step Solution: Identify the architecture: lightweight AP + WLC with CAPWAP tunnels.Map time-critical MAC functions to AP; central policy/forwarding to WLC.Recognize that this is a split of MAC-layer responsibilities, not simply addressing.Select the option that states 802.11 processing is split between AP and controller. Verification / Alternative check: Controller configuration guides show that association, authentication state, and client policy are centrally tracked; AP radios still transmit beacons and respond quickly to probes, confirming the functional split. Why Other Options Are Wrong: A/D: Descriptions of switching/bridging behavior; not about 802.11 function partitioning. C: Merely restates wired vs. wireless addressing; ignores the split of MAC duties. E: Oversimplified; controllers commonly process management/control information as well via CAPWAP control channel. Common Pitfalls: Assuming APs are “thin” to the point of doing almost nothing; in reality they still handle timing-critical RF work in split-MAC designs. Final Answer: The split-MAC architecture splits 802.11 protocol functions between the AP and the controller so both devices process portions of each frame exchange.

Question 6

Wi-Fi Topology — What does Extended Service Set Identifier (ESSID) mean? Your access point is configured as a root AP. In IEEE 802.11 terminology, what does the Extended Service Set Identifier (ESSID) represent in a multi-AP deployment?

Accepted Answer

Introduction / Context: 802.11 networks use identifiers to group basic service sets (BSS) into larger, seamless WLANs. The Extended Service Set (ESS) allows clients to roam between coverage cells while staying on the same logical network name (SSID). Understanding ESS/ESSID helps in designing multi-AP deployments with uniform user experience. Given Data / Assumptions: There are multiple infrastructure APs. They share a wired (or wireless mesh) distribution system. They advertise the same network name (SSID), allowing roaming. Concept / Approach: An ESS is a set of one or more BSSs interconnected by a distribution system (for example, Ethernet). The ESS is identified to clients by an SSID (often called ESSID in some tools). When APs use the same SSID and security settings, clients can reassociate between APs as they move, maintaining connectivity within the same subnet/VLAN if designed accordingly. Step-by-Step Solution: Define BSS: a single AP plus its associated clients.Combine multiple BSSs via a distribution system → ESS.Recognize that the shared SSID represents this ESS to clients.Select the option describing multiple APs with the same SSID joined by a distribution system. Verification / Alternative check: Roaming tests show that devices retain the same network identity when moving between APs sharing SSID and security within the same L2 domain, confirming the ESS concept. Why Other Options Are Wrong: B: Separate SSIDs create separate WLANs, not one ESS for roaming. C: Physical separation alone does not define an ESS. D: Repeater mode is a deployment detail, not the definition of ESS/ESSID. E: SSID/ESSID is standardized; it is not vendor-specific. Common Pitfalls: Assuming ESSID is different from SSID; many tools use ESSID synonymously for the SSID presented by an ESS of multiple APs. Final Answer: Multiple APs broadcasting the same SSID and connected by a common distribution system, forming one extended service set.

Question 7

802.11g Range at Top Speed — Maximum distance while sustaining the maximum data rate In typical indoor conditions, what is the approximate maximum distance at which an 802.11g client can still hold the maximum PHY data rate (54Mbps)?

Accepted Answer

Introduction / Context: PHY data rates in Wi-Fi depend strongly on received signal strength and signal-to-noise ratio (SNR). As distance and obstacles increase, modulation and coding schemes step down. Knowing the ballpark distance at which the top 802.11g rate (54Mbps) can be maintained helps with practical access point placement. Given Data / Assumptions: Indoor office/home environment with walls and typical interference at 2.4GHz. Omnidirectional antennas with standard transmit power. Client is stationary; rate adaptation is enabled. Concept / Approach: 802.11g uses OFDM at 2.4GHz. Highest rate 54Mbps typically requires high SNR (for example, 20–25 dB+ depending on implementation). Practical deployments show that the top rate is sustained over short to moderate distances. As the client moves farther, the rate adapts down (48, 36, 24, 18, 12, 9, 6Mbps). Therefore, the common rule of thumb is roughly 65–75 feet for many indoor environments to keep 54Mbps, although layouts and RF noise can change this significantly. Step-by-Step Solution: Identify the target rate: 54Mbps (highest for 802.11g).Recall required SNR: relatively high, so shorter distance.Apply indoor attenuation expectations at 2.4GHz.Choose the distance range most consistent with sustaining the highest MCS: about 65–75 feet. Verification / Alternative check: Vendor site surveys and heatmaps often show primary cell radii of ~50–75 feet at top rates for 2.4GHz in typical structures. Beyond that, modulation fallback occurs quickly. Why Other Options Are Wrong: 90–100 feet and above: At these distances, most clients drop to lower rates (24Mbps or below). 150 feet or 200+ feet: Usually far beyond the range to keep 54Mbps indoors. 30 feet: Possible, but too conservative; many designs sustain 54Mbps beyond 30 feet. Common Pitfalls: Equating PHY rate with throughput; even at 54Mbps, user throughput is much lower. Also, different buildings and devices vary widely; this is an approximate planning value, not a guarantee. Final Answer: About 65-75 feet

Question 8

Wi-Fi Fundamentals — IEEE 802.11b Maximum Data Rate In the legacy 2.4GHz 802.11b standard (DSSS/CCK), what is the theoretical maximum physical layer (PHY) data rate?

Accepted Answer

Introduction / Context: Before 802.11g/n/ac/ax, early Wi-Fi deployments relied on 802.11b operating at 2.4GHz using DSSS/CCK modulation. Memorizing the maximum PHY rate for 802.11b helps differentiate capabilities across generations of WLAN equipment. Given Data / Assumptions: Standard is IEEE 802.11b. Question targets the PHY headline rate, not application throughput. Environment is ideal for the purpose of nominal rate. Concept / Approach: 802.11b defined rates of 1, 2, 5.5, and 11Mbps using DSSS and CCK. Hence, the maximum data rate is 11Mbps. Remember that effective throughput at 11Mbps is far lower (often under 6Mbps TCP) due to medium contention, ACKs, and MAC overheads, especially in mixed b/g networks where protection mechanisms further reduce performance. Step-by-Step Solution: Identify modulation family: DSSS/CCK for 802.11b.Recall rate set: 1, 2, 5.5, 11Mbps.Select the highest value: 11Mbps.Confirm that 54Mbps is associated with 802.11a/g, not 11b. Verification / Alternative check: Any 802.11 reference table lists 11Mbps as the 802.11b maximum; routers/AP specs from the 2000s commonly show “802.11b: up to 11Mbps.” Why Other Options Are Wrong: 6Mbps: OFDM basic rate for 802.11a/g; not 11b. 22Mbps: Proprietary extensions existed, but not part of the 802.11b standard. 54Mbps: 802.11a/g, not b. 2Mbps: A valid legacy rate but not the maximum. Common Pitfalls: Confusing vendor “Turbo” modes or mixed b/g overheads with standardized headline rates. Final Answer: 11Mbps

Question 9

Cisco Unified Wireless Mesh — Minimum components to purchase Cisco's Unified Wireless Solution supports mesh networking. Which minimum set of devices must you have to run a Cisco mesh deployment?

Accepted Answer

Introduction / Context: Enterprise Cisco WLANs commonly use lightweight access points (LAPs) joined to a Wireless LAN Controller (WLC). In a mesh deployment, APs may function as mesh root or mesh nodes, but centralized control remains central to Cisco's Unified Wireless architecture. Understanding which components are required versus optional avoids unnecessary purchases. Given Data / Assumptions: The question targets the essential components for Cisco's mesh solution. “WCS” (legacy Wireless Control System) or Cisco Prime Infrastructure provides management/monitoring, not core forwarding/control. Specialized “bridge” hardware is not mandatory for modern lightweight mesh AP deployments. Concept / Approach: A lightweight AP needs to join a WLC to operate in Unified mode. Mesh roles (root and mesh APs) still register to the controller via CAPWAP and rely on WLC for control-plane policy, client state, and mobility. Therefore, at minimum you need a WLC and compatible mesh-capable APs. Management platforms like WCS/Prime add convenience but are not strictly required for functionality. A standalone bridge may be used in specific point-to-point links, but it is not an absolute requirement for Unified mesh WLAN. Step-by-Step Solution: List possible components: WCS/Prime (management), WLC (control), LAPs (radios), optional bridges.Identify mandatory control-plane: WLC.Identify mandatory RF endpoints: Access points.Select “Controller and Access point.” Verification / Alternative check: Controller configuration guides show mesh AP registration and operation dependent on an available WLC; without a controller, LAPs cannot serve clients in Unified mode. Why Other Options Are Wrong: WCS + Controller: WCS is optional; APs are still required. Bridge only: Not a Unified mesh solution; lacks controller and AP infrastructure. WCS + Bridge only / AP only: Missing the WLC, so Unified mesh cannot operate. Common Pitfalls: Confusing autonomous (controller-less) APs with Unified (controller-based) deployments; the mesh feature discussed here refers to the latter. Final Answer: Controller and Access point

Question 10

802.11a Frequency Band — Choose the correct range Which frequency band does IEEE 802.11a use for wireless LAN operation?

Accepted Answer

Introduction / Context: Different Wi-Fi amendments operate in different bands, which impacts channel availability, interference, and propagation. 802.11a was the first widely used OFDM-based Wi-Fi at higher frequencies than 2.4GHz, providing more non-overlapping channels but shorter range through obstacles. Given Data / Assumptions: We are choosing the correct frequency band, not throughput. 802.11a uses OFDM with 20MHz channels in 5GHz UNII bands. Units matter: GHz (frequency) vs. Gbps (throughput). Concept / Approach: 802.11a operates exclusively in the 5GHz band. Confusions often arise because 802.11g also reaches 54Mbps but at 2.4GHz. Options that say “Gbps” are unit traps (throughput units), not frequency. Selecting the 5GHz option identifies the correct band for 802.11a. Step-by-Step Solution: Recall mapping: 802.11b/g → 2.4GHz; 802.11a → 5GHz.Ignore options with Gbps (throughput unit, not frequency).Choose 5GHz as the correct band. Verification / Alternative check: Any Wi-Fi quick reference shows 802.11a: 5GHz, 54Mbps max PHY (legacy), 12+ channels depending on regulatory domain. Why Other Options Are Wrong: 2.4GHz: That is 802.11b/g (and 802.11n can use both bands). Gbps answers: Wrong units; they denote data rates, not RF frequency. 900MHz: Not an 802.11a band. Common Pitfalls: Mixing up 802.11a and 802.11g because both show 54Mbps; band (5GHz vs. 2.4GHz) is the differentiator. Final Answer: 5GHz

Question 11

802.11g Frequency Band — Choose the correct range Which frequency band does IEEE 802.11g use for wireless LAN operation?

Accepted Answer

Introduction / Context: 802.11g brought OFDM to the 2.4GHz band while retaining backward compatibility with 802.11b clients. Knowing which band each amendment uses is foundational for channel planning and interference management in WLAN design. Given Data / Assumptions: We are selecting the RF band, not a throughput value. 802.11g is the 2.4GHz counterpart to 802.11a's OFDM approach. Standard channel widths are 20MHz in legacy g deployments. Concept / Approach: 802.11g operates strictly in 2.4GHz, supporting a maximum PHY rate of 54Mbps and backward compatibility with 802.11b. Answers with “Gbps” are unit traps; they indicate data rates, not frequencies. Therefore, 2.4GHz is the correct choice. Step-by-Step Solution: Map amendments to bands: 11b/g → 2.4GHz; 11a → 5GHz.Eliminate options using Gbps units.Choose 2.4GHz. Verification / Alternative check: Any Wi-Fi study guide lists 802.11g at 2.4GHz with OFDM and DSSS coexistence mechanisms for backward compatibility. Why Other Options Are Wrong: 5GHz: That is 802.11a (and 11n/ac/ax can also use it). Gbps options: Throughput units, not frequency. 900MHz: Not used by 802.11g. Common Pitfalls: Assuming 802.11g “moved to 5GHz” because it gained OFDM; only 11a was 5GHz in the legacy pair. Final Answer: 2.4GHz

Question 12

Channel Planning — Non-overlapping channels available with 802.11g (2.4GHz) In the 2.4GHz band as used by IEEE 802.11g, how many non-overlapping 20MHz channels are available in most regulatory domains (for example, channels 1, 6, and 11)?

Accepted Answer

Introduction / Context: Effective 2.4GHz WLAN design hinges on proper channel reuse. Because adjacent channels overlap significantly in 2.4GHz, only a small subset of channels can be reused without co-channel or adjacent-channel interference. Designers typically rely on the classic trio for minimal overlap. Given Data / Assumptions: Channel width is 20MHz. Regulatory domain similar to North America with channels 1–11. Goal is to count non-overlapping channels in typical planning. Concept / Approach: With 20MHz channels in 2.4GHz and center-frequency spacing of 5MHz, adjacent channels overlap. The conventional non-overlapping set in many domains is channels 1, 6, and 11. Some regions allow channel 13, enabling different triplets, but the standard practice still yields three non-overlapping channels. This limitation drives many enterprises toward 5GHz for higher capacity. Step-by-Step Solution: Confirm band and width: 2.4GHz, 20MHz channels.Recall typical non-overlapping set: 1/6/11.Count the set size: 3.Select “3.” Verification / Alternative check: Site surveys and vendor guides consistently recommend a 3-channel reuse plan in 2.4GHz for minimal interference in most regions. Why Other Options Are Wrong: 12, 23, 40: Numbers more typical of 5GHz channels, not 2.4GHz non-overlapping counts. 4: Occasionally cited in special cases (different channel widths/regional rules), but standard 20MHz planning widely uses 3. Common Pitfalls: Assuming every listed channel is usable concurrently; overlap constraints limit practical non-overlapping choices to three in most domains. Final Answer: 3

Question 13

802.11b Range at Top Speed — Maximum distance while sustaining 11Mbps In typical indoor conditions, what is the approximate maximum distance at which an 802.11b client can still hold its maximum PHY data rate of 11Mbps?

Accepted Answer

Introduction / Context: As distance increases and signal quality drops, Wi-Fi devices fall back to lower data rates. 802.11b (DSSS/CCK at 2.4GHz) requires a good SNR to hold 11Mbps. Understanding the approximate range for the top rate helps with legacy design considerations and interpreting client behavior in mixed environments. Given Data / Assumptions: Indoor environment with typical walls and interference. Standard omnidirectional antennas and transmit power. Client and AP are stationary; rate adaptation is active. Concept / Approach: 802.11b's maximum 11Mbps is more tolerant than OFDM's highest rates but still needs adequate SNR. Many deployments observe that 11Mbps can be sustained to roughly 90–100 feet indoors before stepping down to 5.5, 2, or 1Mbps. These are approximate values; building materials, interference sources (microwaves, Bluetooth), and device radios significantly influence actual performance. Step-by-Step Solution: Identify target rate: 11Mbps (802.11b max).Relate rate vs. SNR vs. distance: farther distance → lower SNR → lower rate.Use common planning heuristics indicating ~90–100 feet at 11Mbps indoors.Choose the closest matching range. Verification / Alternative check: Historical vendor datasheets and independent site surveys show client speed tests at roughly 90–100 feet sustaining 11Mbps under good conditions; beyond this, fallbacks are typical. Why Other Options Are Wrong: 65–75 feet: Too conservative; 11Mbps often holds further than that. 150 feet / over 200 feet: Unrealistic for sustaining the maximum 11Mbps indoors. 30 feet: Far below practical expectations in typical layouts. Common Pitfalls: Confusing PHY rate with throughput; even at 11Mbps, user throughput will be far lower. Real-world range varies, so these numbers guide expectations rather than guarantee performance. Final Answer: About 90-100 feet

Question 14

Wireless networking (IEEE 802.11a): How many non-overlapping 20-MHz channels are available in the 5 GHz 802.11a band (typical U.S. regulatory domain)?

Accepted Answer

Introduction / Context: Channel planning is a core skill in Wi-Fi design. Unlike 2.4 GHz (802.11b/g/n), the 5 GHz band used by 802.11a offers many more non-overlapping channels, enabling denser deployments with less co-channel interference. Given Data / Assumptions: Standard: IEEE 802.11a (5 GHz band). Channel width considered: 20 MHz (legacy 11a operation). Regulatory domain: U.S. (common exam assumption). Concept / Approach: Non-overlapping channels are center frequencies spaced so 20-MHz channels do not overlap. In 5 GHz, the U-NII bands provide far more such channels than the three non-overlapping channels commonly available at 2.4 GHz, which is why 5 GHz scales better. Step-by-Step Solution: Recognize that 802.11a operates in multiple U-NII bands with many 20-MHz channels.Count of non-overlapping 20-MHz channels commonly cited for the U.S. domain is 23.Therefore, choose 23 as the correct planning number for classic 11a. Verification / Alternative check: Vendor design guides and CWNA-level materials list 23 usable 20-MHz channels (subject to DFS/TPC requirements) for U.S. indoor planning, confirming the common answer. Why Other Options Are Wrong: 3: This is the 2.4 GHz non-overlapping count, not 5 GHz. 12/40/8: Do not match the standard planning count used for 11a 20-MHz channels in the U.S. Common Pitfalls: Confusing regulatory domains; mixing 20-MHz channel counts with bonded widths (40/80/160 MHz) which reduce the number of available channels. Final Answer: 23

Question 15

Wi-Fi bands (IEEE 802.11b): What frequency range does the 802.11b standard operate in?

Accepted Answer

Introduction / Context: Understanding which IEEE 802.11 standard uses which frequency band is fundamental for troubleshooting and planning wireless networks, especially regarding interference and channel availability. Given Data / Assumptions: Standard in question: IEEE 802.11b. Answers mix units of rate (Gbps) with units of frequency (GHz), a common distractor tactic. Concept / Approach: 802.11b is a legacy Wi-Fi standard that operates exclusively in the 2.4 GHz ISM band (roughly 2.4–2.4835 GHz). It introduced data rates up to 11 Mbps using DSSS/CCK modulation. Step-by-Step Solution: Identify that only options labeled in frequency units (GHz) are meaningful for a band question.Recall: 802.11b = 2.4 GHz; 802.11a = 5 GHz.Select 2.4GHz as the correct band. Verification / Alternative check: Any Wi-Fi primer or certification guide (e.g., CCNA Wireless, CWNA) lists 802.11b/g/n (legacy modes) as 2.4 GHz capable and 802.11a/ac/ax (modes) as 5 GHz capable. Why Other Options Are Wrong: 2.4Gbps / 5Gbps: Throughput units, not frequency; irrelevant to “range”. 5GHz: That is for 802.11a (and later 5 GHz-capable amendments), not b. 900MHz: Used by other technologies, not 802.11b. Common Pitfalls: Confusing frequency bands with data rates; assuming all Wi-Fi runs at 5 GHz because it is “faster”. Final Answer: 2.4GHz

Question 16

Cisco mesh networking: In a Cisco wireless mesh, which protocol lets multiple access points form a mesh with redundant multi-hop paths between nodes?

Accepted Answer

Introduction / Context: Mesh WLANs provide wireless backhaul between access points (APs), maintaining connectivity even if some links fail. Cisco mesh uses a proprietary path selection protocol tuned for RF conditions. Given Data / Assumptions: Technology: Cisco Aironet/Catalyst mesh networks. Goal: Form a resilient mesh with multiple redundant links between AP nodes. Concept / Approach: Cisco uses AWPP (Adaptive Wireless Path Protocol) to dynamically choose best paths in a mesh based on link quality and other metrics. This is distinct from control/management tunnels or generic Layer 2 loop prevention. Step-by-Step Solution: Identify role: multi-hop, adaptive path selection in a Cisco mesh.Match to AWPP, Cisco’s purpose-built mesh protocol.Eliminate protocols that do not provide RF mesh path selection. Verification / Alternative check: Cisco mesh design guides explicitly reference AWPP as the mesh routing/path selection mechanism. Why Other Options Are Wrong: LWAPP: Control/management tunneling protocol, not mesh path selection. STP: Layer 2 loop prevention for Ethernet, not wireless mesh routing. IEEE: Not a protocol—standards body. RPL: An IoT routing protocol, not Cisco’s enterprise Wi-Fi mesh method. Common Pitfalls: Assuming STP applies to RF backhaul; confusing control protocols (LWAPP/CAPWAP) with mesh routing. Final Answer: AWPP

Question 17

Throughput of legacy Wi-Fi: What is the maximum data rate defined by the IEEE 802.11a standard?

Accepted Answer

Introduction / Context: Legacy Wi-Fi standards have headline data rates that are frequently referenced in certification exams and design discussions. 802.11a introduced OFDM at 5 GHz with a maximum PHY rate of 54 Mbps per 20-MHz channel. Given Data / Assumptions: PHY data rate, not real-world throughput. Single 20-MHz channel, standard 11a modulation and coding. Concept / Approach: 802.11a’s OFDM supports multiple rates: 6, 9, 12, 18, 24, 36, 48, and 54 Mbps, with 54 Mbps being the top PHY rate under ideal conditions. Step-by-Step Solution: Recall the 802.11a rate set.Identify the highest rate in the mandatory/extended set: 54 Mbps.Select 54 Mbps as the defined maximum PHY rate. Verification / Alternative check: Standards summaries and vendor datasheets consistently list 54 Mbps as the maximum 802.11a rate. Why Other Options Are Wrong: 6/11/22 Mbps: Valid in other contexts (e.g., 802.11b 11 Mbps, PBCC 22 Mbps) but not the 11a maximum. 108 Mbps: Vendor “turbo” or channel bonding marketing, not standard 11a. Common Pitfalls: Confusing PHY rates with application throughput; mixing 11a with 11b/g figures. Final Answer: 54 Mbps

Question 18

802.11g coverage at lowest rate: Approximately how far can an 802.11g link reach indoors when operating at its lowest fallback data rate under typical conditions?

Accepted Answer

Introduction / Context: Wi-Fi range depends on modulation, coding, interference, obstacles, and transmit power. As the data rate drops to the lowest fallback, the required signal-to-noise ratio decreases, allowing greater reach. Given Data / Assumptions: Standard: 802.11g operating in 2.4 GHz indoors. “Typical” enterprise/home environment, not line-of-sight outdoor. Lowest data rate (e.g., 1–6 Mbps depending on supported basic rates). Concept / Approach: At the lowest supported rate, robust modulation schemes tolerate lower SNR and multipath, increasing coverage. Many design guides cite indoor coverage up to roughly 300 feet at the lowest 802.11g rates, though performance is highly environment-dependent. Step-by-Step Solution: Note typical indoor ranges: tens of meters at high rates, increasing at low rates.Select the commonly cited indoor figure: about 300 feet for 11g at the lowest rate.Acknowledge variability due to walls, interference, and antenna gain. Verification / Alternative check: Vendor deployment guides and Wi-Fi textbooks often publish 100–300 ft indoor ranges; the longest typical number presented for 11g at low rates is near 300 ft. Why Other Options Are Wrong: 100/175 ft: More consistent with moderate rates. 350 ft: Possible in very favorable conditions but less typical indoors. Common Pitfalls: Treating any range as guaranteed; ignoring regulatory power limits and interference from Bluetooth/microwaves in 2.4 GHz. Final Answer: About 300 feet

Question 19

802.11a coverage at maximum rate: At the highest 802.11a data rate (54 Mbps), what is the typical maximum indoor distance achievable?

Accepted Answer

Introduction / Context: 5 GHz links (802.11a) provide higher data rates but generally shorter range than 2.4 GHz due to higher path loss and reduced wall penetration. At the top PHY rate, the SNR requirement is highest, limiting reach. Given Data / Assumptions: Standard: 802.11a, 5 GHz, 20-MHz channel, 54 Mbps PHY. Indoor environment with typical attenuation. Concept / Approach: Maximum rate requires robust SNR. Indoor design references frequently quote ~65–75 ft (20–23 m) for 54 Mbps stability in normal buildings; rates drop as you move farther from the AP. Step-by-Step Solution: Consider 5 GHz attenuation vs 2.4 GHz.Recall typical vendor guidance for 54 Mbps indoor coverage: around 65–75 ft.Select that range as the best answer. Verification / Alternative check: AP data sheets and site survey guides match this order of magnitude for high-rate service areas. Why Other Options Are Wrong: 90–100/150/200+ ft: More consistent with lower rates (e.g., 24, 12, or 6 Mbps). 30 ft: Too conservative for typical interior offices. Common Pitfalls: Assuming all 5 GHz coverage is short; rate adaptation will extend distance by lowering the PHY rate. Final Answer: About 65–75 feet

Question 20

802.11a coverage at lowest rate: Indoors, what is the typical maximum distance for an 802.11a link operating at its lowest fallback data rate?

Accepted Answer

Introduction / Context: As Wi-Fi lowers its data rate, it can hold a connection at longer distances because the required SNR drops. For 802.11a (5 GHz), the “low-rate” coverage is shorter than comparable 2.4 GHz due to higher path loss and DFS constraints. Given Data / Assumptions: Standard: 802.11a at 5 GHz, indoors. Lowest rate (for many profiles: 6 Mbps). Typical office attenuation and multipath. Concept / Approach: Common planning figures show roughly ~150 ft for lowest-rate 5 GHz indoor coverage. This is shorter than 2.4 GHz at the lowest rates (often ~300 ft), yet still considerably longer than the highest-rate coverage area at 54 Mbps. Step-by-Step Solution: Recognize 5 GHz has less range than 2.4 GHz at similar rates.Use typical design heuristics: ~150 ft for 11a low-rate indoor coverage.Choose the closest listed value. Verification / Alternative check: Site survey experiences and vendor reference designs corroborate this order of magnitude for 5 GHz low-rate distances. Why Other Options Are Wrong: 100 ft: Often too conservative for the lowest rate. 175/300/350 ft: Either optimistic for 5 GHz or more aligned with 2.4 GHz (11g) low-rate reach. Common Pitfalls: Assuming 5 GHz and 2.4 GHz reach the same distances; ignoring building construction, which can alter results substantially. Final Answer: About 150 feet

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