Cisco Designing Cisco Enterprise Wireless Networks (ENWLSD) (300-425)

✅

Reasoning: For Layer 3 roaming within a Cisco mobility group, all WLCs must be configured with the exact same virtual IP address. This ensures clients maintain their IP address and session state when roaming between controllers within the group. ❌ Why the other choices are incorrect:

• Option A is incorrect: The virtual IP address is not typically tied to a DNS entry; it's an internal, non-routable address used by controllers for mobility functions.
• Option B is incorrect: While management interface IPs must be unique, the question refers to the virtual IP address, which must be the same across mobility group members.
• Option C is incorrect: Defining a DNS Host Name is for identification and management, but it's not a rule governing the virtual IP configuration for proper roaming.

✅ **85 to -67 dBm **

Reasoning: Cisco's wireless voice design guidelines specify -67 dBm as the minimum RSSI for reliable voice operation. The voice readiness tool in Cisco Prime inspects network signal levels from approximately -85 dBm (a common lower limit for Wi-Fi signal detection and evaluation) up to -67 dBm to identify areas that meet or fall below the voice quality threshold. ❌ Why the other choices are incorrect:

• Option A is incorrect: This range does not accurately reflect the critical -67 dBm voice threshold and starts too strong at -78 dBm to inspect for very weak, problematic signals.
• Option B is incorrect: This range is too narrow and too strong at the lower end (-72 dBm), failing to encompass the full spectrum of potentially insufficient signal strengths relevant for voice readiness.
• Option C is incorrect: While -85 dBm is a plausible lower bound, the upper limit of -65 dBm is stronger than the standard -67 dBm voice minimum, making -85 to -67 dBm a more precise inspection range for evaluating against the critical threshold.

✅ **fewer antennas than laptops **

Reasoning: Smartphones and tablets commonly use 1x1 or 2x2 MIMO, meaning 1 or 2 antennas. Laptops often incorporate 2x2 or 3x3 MIMO, offering more spatial streams and better performance. This directly impacts signal quality and throughput for real-time traffic.

Reasoning: Due to fewer antennas (as per option C), smaller physical size, and potentially lower transmit power, smartphones/tablets generally achieve lower maximum data rates compared to most laptops. This is a crucial consideration for real-time application performance. ❌ Why the other choices are incorrect:

• Option A is incorrect: Modern smartphones and tablets widely support 802.11ac, and increasingly 802.11ax, so this statement is factually inaccurate.
• Option B is incorrect: Laptops, typically with more antennas (e.g., 2x2 or 3x3 MIMO), generally achieve higher maximum data rates than smartphones/tablets.
• Option D is incorrect: Current smartphones and tablets support 802.11r (Fast BSS Transition) for quicker roaming, essential for uninterrupted real-time traffic.

✅

Reasoning: In a warehouse with internal, often omnidirectional antennas, mounting access points too high causes the RF signal to project over client devices, resulting in low signal strength and poor coverage at user level.

Reasoning: Warehouses contain numerous materials like metal shelving, inventory (e.g., liquids, densely packed boxes), and machinery that absorb RF signals. This absorption significantly attenuates signal strength, leading to reduced coverage, dead zones, and diminished user experience. ❌ Why the other choices are incorrect:

• Option A is incorrect: Wireless channels are a resource. Improper channel planning causes issues, but the channels themselves are not inherently negative elements.
• Option C is incorrect: Client authentication is a necessary security measure; it does not negatively impact wireless performance or coverage for a connected user.
• Option D is incorrect: Client authorization is a security and policy enforcement mechanism; it does not negatively affect the RF environment or signal quality.

In standard wireless networking architectures (like Cisco WLC), the correct statement is B.

Why Statement B is True:

Priority 4 (Critical): This is the highest priority level available for AP failover.

Behavior: When a Primary Controller fails, the controller looks at these priority values. Access points marked as Priority 4 (Critical) are processed first, ensuring they join a backup controller before those with lower priority levels (like Priority 1, which is Low).

Breakdown of the Priority Scale:

Priority 4: Critical (Highest)

Priority 3: High

Priority 2: Medium

Priority 1: Low (Lowest)

✅ Ensure that the UNII-2 extended channels are enabled on the 802.11a radios.

Reasoning: Enabling UNII-2 extended channels (e.g., 100-144) increases the available 5 GHz channel pool. A wider range of channels provides more options for APs, reduces contention, and allows for better DFS flexibility, which significantly enhances the overall availability and capacity of the 5 GHz band, thereby promoting client utilization.

Reasoning: This is a fundamental requirement. If a client device lacks the hardware to support 5 GHz (i.e., it's not dual-band capable), it cannot detect, associate with, or use the 5 GHz band, regardless of any other configuration.

Reasoning: The 802.11a standard (and its extensions like 802.11n/ac/ax in 5 GHz) must be enabled on the WLAN and the AP's 5 GHz radio. If 5 GHz capabilities are not active on the WLAN, the network will not broadcast on this band, preventing clients from connecting to it. ❌ Why the other choices are incorrect:

• Option A is incorrect: Channel bonding (e.g., 40/80/160 MHz) enhances throughput but is not a prerequisite for clients to simply use the 5 GHz band. Clients can still connect to 20 MHz 5 GHz channels.
• Option B is incorrect: Co-channel interference levels relate to performance and signal quality, not the fundamental ability for clients to use the 5 GHz band. High CCI impacts experience, but not basic connectivity if the band is enabled.
• Option D is incorrect: While important for successful band steering to 5 GHz, client RSSI above a minimum threshold isn't a fundamental parameter for the possibility of 5 GHz usage. The client must first be capable and the band available, regardless of initial RSSI.

✅ **The client device must have at least an -67 dBm RSSI. **

Reasoning: Cisco best practices for enterprise voice over WLAN consistently recommend a minimum Received Signal Strength Indicator (RSSI) of -67 dBm or stronger for reliable voice communication, ensuring adequate signal quality for real-time traffic.

Reasoning: High packet retransmission rates severely degrade voice quality. While lower rates (e.g., 10-15%) are ideal, a rate of 20% or below is often cited as the upper limit for basic "acceptable" voice support before quality becomes widely unacceptable. ❌ Why the other choices are incorrect:

• Option A is incorrect: A noise floor that "does not exceed -87 dBm" means it's -87 dBm or lower (e.g., -90 dBm). While lower noise is good, the primary metric for voice is typically Signal-to-Noise Ratio (SNR), not just noise floor in isolation. An SNR of at least 25 dB is usually required.
• Option C is incorrect: While a retransmission rate of 15% or below is excellent and preferred for optimal voice, option D (20% or below) represents the threshold for acceptable support based on various Cisco deployment guides for voice.
• Option E is incorrect: While -65 dBm RSSI is excellent, -67 dBm is the specific minimum threshold Cisco recommends for voice services. The question asks for a metric to ensure support, and -67 dBm is the defined lower bound.

✅

Reasoning: A PoE battery provides portable power for the access point, enabling it to operate and broadcast signals at various survey locations without requiring an AC outlet. This is crucial for mobility during the survey.

Reasoning: An access point is fundamental to a fully measured survey, often called an "AP-on-a-stick" survey. It emits the wireless signals that are measured by the survey client, generating actual RF data for analysis.

Reasoning: A tall tripod (or survey mast) is essential to position the access point at the planned deployment height. This simulates the actual installation, ensuring accurate signal propagation measurements. ❌ Why the other choices are incorrect:

• Option B is incorrect: A spirit level helps ensure precise installation alignment but is not strictly necessary for the RF measurement process itself.
• Option E is incorrect: Goggles are personal protective equipment unrelated to the technical requirements for conducting a wireless survey.
• Option F is incorrect: While a ladder could potentially be used, a tall tripod is the standard and more practical equipment for safely and repeatedly positioning an AP at various heights during a survey.

✅ The high priority access point is oversubscribed.

Reasoning: The backup WLC has 10 licenses. Five high priority APs will attempt failover first, consuming 5 licenses. This leaves only 5 licenses for the 7 critical priority APs. The high priority APs' consumption, given their precedence, effectively oversubscribes the available licenses for subsequent lower priority APs, causing some critical APs to not fail over.

✅

Reasoning: The ping command is the standard and most fundamental CLI utility on Cisco devices, including wireless controllers, used to verify basic IP connectivity and reachability to a remote host, such as a redundancy peer in an SSO pair. ❌ Why the other choices are incorrect:

• Option A is incorrect: rping is not a standard Cisco CLI command for validating peer connectivity in this context.
• Option C is incorrect: eping is not a standard Cisco CLI command for validating peer connectivity.
• Option D is incorrect: mping is typically used to test multicast reachability, not general unicast IP connectivity to a specific redundancy peer.