Pass the HP Aruba Certified Design Professional (ACDP) V1 HPE6-A47 Questions and answers with ExamsMirror

 A collision domain is a logical area of the network where devices share the same wireless medium and may interfere with each other’s transmissions. In a WLAN, a collision domain is defined by the channel and the coverage area of an AP or a client. Devices that operate on the same channel and are within range of each other belong to the same collision domain and must contend for access to the medium using the Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) protocol. Devices that operate on different channels or are out of range of each other belong to different collision domains and do not interfere with each other.

In this scenario, the architect plans 12 APs for an auditorium that is 325 square meters (3,498 square feet). Each AP has one 2.4 GHz radio and one 5 GHz radio. Both types of radios use 20 MHz channels. Assuming that DFS channels can be used in this design, the question is how many 5 GHz collision domains does this design provide.

To answer this question, we need to consider the following factors:

The number of available 5 GHz channels in the regulatory domain of the auditorium. Different countries have different regulations on the use of the 5 GHz band, which affects the number and availability of channels for WLANs. For example, in the United States, there are 25 non-overlapping 20 MHz channels in the 5 GHz band, but some of them are subject to Dynamic Frequency Selection (DFS) requirements, which means that they must avoid interfering with radar systems by detecting and switching to another channel if radar signals are present. In other countries, such as Japan, there are 19 non-overlapping 20 MHz channels in the 5 GHz band, but some of them are restricted to indoor use only. Therefore, the number of available 5 GHz channels for the design depends on the regulatory domain of the auditorium.

The channel assignment and distribution of the 12 APs in the auditorium. The channel assignment and distribution of the APs affect the number and size of the collision domains in the WLAN. Ideally, the APs should be assigned to non-overlapping channels and distributed evenly across the auditorium to provide optimal coverage and capacity, while minimizing co-channelinterference and adjacent channel interference. Co-channel interference occurs when devices on the same channel interfere with each other, while adjacent channel interference occurs when devices on nearby channels interfere with each other. Both types of interference degrade the performance and quality of the WLAN. Therefore, the channel assignment and distribution of the APs should follow the best practices of RF design, such as using a channel reuse plan, avoiding channel overlap, and adjusting the transmit power and antenna gain of the APs to match the coverage and capacity requirements of the auditorium.

The coverage and capacity requirements of the auditorium. The coverage and capacity requirements of the auditorium affect the number and placement of the APs and the transmit power and antenna gain settings of the radios. The coverage requirement refers to the minimum signal strength and signal-to-noise ratio (SNR) that the APs and clients need to maintain a reliable wireless connection. The capacity requirement refers to the maximum number of clients and the minimum throughput and quality of service (QoS) that the APs and clients need to support the applications and services of the auditorium. The coverage and capacity requirements of the auditorium depend on the size and shape of the space, the density and distribution of the clients, the types and characteristics of the applications and services, and the performance and capabilities of the devices. Therefore, the coverage and capacity requirements of the auditorium should be determined by conducting a site survey and a network analysis, and then used to guide the design and configuration of the APs and radios.

Based on these factors, we can estimate the number of 5 GHz collision domains in the design as follows:

Assuming that the auditorium is located in the United States and that DFS channels can be used in the design, there are 25 non-overlapping 20 MHz channels in the 5 GHz band. However, not all of them may be available or suitable for the design, depending on the presence and activity of radar systems in the area, the compatibility and support of the APs and clients, and the interference and noise level of the environment. Therefore, we will use a conservative estimate of 15 available 20 MHz channels in the 5 GHz band for the design.

Assuming that the 12 APs are assigned to non-overlapping channels and distributed evenly across the auditorium, each AP will have its own 5 GHz collision domain, as there will be no co-channel interference or adjacent channel interference among the APs. Therefore, there will be 12 5 GHz collision domains in the design, corresponding to the 12 APs.

Assuming that the coverage and capacity requirements of the auditorium are moderate and that the transmit power and antenna gain settings of the radios are adjusted accordingly, each AP will cover an area of about 27 square meters (290 square feet), which is roughly the size of a small classroom. This means that the APs will provide adequate signal strength and SNR for the clients, while avoiding excessive overlap and interference among the APs. Therefore, there will be no need to further divide or merge the 5 GHz collision domains in the design, as they will match the coverage and capacity requirements of the auditorium.

Hence, the number of 5 GHz collision domains in the design is 12, which is the answer option C. References:

RF Design | Validated Solution Guide - Aruba

Configuring 2.4 Ghz and 5 Ghz Radios - Aruba

Chapter T-5: Understanding RF Collision Domains - Aruba

[Aruba Certified Design Professional Official Certification Study Guide (HPE6-A47)]

According to the Aruba Validated Design: Campus Wireless LAN1, MCs that are in different subnets cannot form a cluster, which is a logical group of MCs that share the same configuration and provide redundancy and load balancing for each other. However, MCs that are in different subnets can still provide backup LMS (local mobility switch) functionality for each other’s APs. This means that if the primary MC that controls an AP fails, the AP can fail over to the backup MC that is in a different subnet. However, this failover is not stateful, meaning that the user sessions and firewall states are not preserved. Therefore, option D is the correct answer.

Option A is incorrect because the MCs can provide some level of redundancy for each other without being in the same subnet, as explained above. Option B is incorrect because VRRP is not required to provide redundancy for MCs that are in different subnets. VRRP is a protocol that provides redundancy for routers by creating a virtual router with a shared IP address. However, MCs do not act as routers, and they do not need a shared IP address to provide backup LMS functionality. Option C is incorrect because the MCs cannot be in a cluster if they are in different subnets, as explained above. Therefore, the cluster will not support any features, such as stateful failover, load balancing, or centralized configuration. References: Aruba Validated Design: Campus Wireless LAN)

The frequency of the radio wave is one of the most important factors that determines the antenna performance and compatibility. The antenna must be designed to operate at the same frequency band as the radio, otherwise the impedance mismatch will cause signal loss and reflection. The frequency also affects the size, shape, and radiation pattern of the antenna. For example, a lower frequency requires a larger antenna to achievethe same gain and directivity as a higher frequency antenna. The frequency also determines the available bandwidth and channel spacing for the wireless communication12. Therefore, it is essential to ensure that the antenna is designed for the frequency used by the radio. References:

1: Antenna selection guidelines - STMicroelectronics

2: Guide to Selecting the Right Antenna - Telco Antennas

A wide sector directional antenna is a type of antenna that radiates or receives radio waves in a sector-shaped pattern, covering a wide angle of a circle. The width of the sector is determined by the horizontal beamwidth (H-plane) of the antenna, while the height of the sector is determined by the vertical beamwidth (E-plane) of the antenna12. A wide sector directional antenna is usually used to provide regional coverage for wireless networks, such as Wireless Internet Service Providers (WISP) or similar applications2.

According to the antenna specifications given, Antenna 3 has the widest horizontal beamwidth of 100 degrees, which means it can cover a large sector of a circle. Antenna 4 has a narrower horizontal beamwidth of 60 degrees, which means it can cover a smaller sector of a circle. Antenna 1 and Antenna 2 have a horizontal beamwidth of 360 degrees, which means they are omnidirectional antennas, not directional antennas. Therefore, Antenna 3 is the best choice for the plan that specifies wide sector directional antennas.

References:

1: https://en.wikipedia.org/wiki/Sector_antenna

2: https://lcantennas.com/directional-antennas/

An active site survey is a method of measuring and validating the wireless coverage, capacity, and performance of a network in a specific environment. It involves deploying temporary APs in the proposed locations, collecting data using a survey tool, and analyzing the results to optimize the network design. A heat map is a graphical representation of the wireless signal strength, interference, noise, or other metrics in different areas of the site. A heat map with proposed AP locations and actual tested coverage is a deliverable that shows the customer the expected performance of the new 802.11ac-based solution, and allows the architect to fine-tune the AP placement, channel selection, transmit power, and antenna orientation. This deliverable also helps the customer to verify that the network meets their requirements for coverage, capacity, and quality of service. References:

Aruba Certified Design Professional Official Certification Study Guide (HPE6-A47) - Chapter 5)

Aruba Validated Reference Design: Wireless LAN Site Surveys - Chapter 3)

Aruba Validated Reference Design: 802.11ac Networks - Chapter 4)

ClearPass Access licenses are required for each unique endpoint that authenticates to ClearPass using any supported protocol, such as 802.1X, MAC authentication, web authentication, or VPN authentication1. ClearPass Onboard licenses are required for each unique endpoint that is provisioned with a certificate using the ClearPass Onboard service2. In this scenario, the customer has 900 employees and up to 30 guests a day, which means there are at most 930 users who need to authenticate to the network. Assuming each user has about two or three devices, the maximum number of devices that need Access licenses is 930 x 3 = 2790, which can be rounded up to 3000. The customer also wants to use certificates to authenticate user devices, which means they need Onboard licenses as well. However, the customer only issues laptops to the employees, which means only 900 devices need Onboard licenses. Therefore, the architect should include 3000 Access licenses and 1000 Onboard licenses in the proposal. References:

1: ClearPass Licensing Guide - Aruba

2: ClearPass Onboard Data Sheet - Aruba

To route at the core and extend some of the same VLANs in different buildings, the architect should recommend creating a backplane stack at the aggregation layer and a VSF fabric at the core. A backplane stack is a logical switch that combines multiple physical switches into a single unit, using dedicated stacking cables or ports. A VSF fabric is a virtual switch that combines multiple physical switches into a single unit, using standard Ethernet links. Both technologies provide high availability, scalability, and simplified management for the network12.

By creating a backplane stack at the aggregation layer, the architect can reduce the number of routing interfaces and routing protocols needed at the core layer, as well as simplify the configuration and maintenance of the aggregation switches. By creating a VSF fabric at the core layer, the architect can enable Layer 2 connectivity across different buildings, as well as provide redundancy and load balancing for the core switches. The VSF fabric can use Multi-Chassis Link Aggregation (MC-LAG) to extend the same VLANs to different aggregation stacks, without creating loops or blocking ports3.

The other options are not suitable for the customer’s requirements. Implementing broadcast filtering on switch-to-switch links across all of the buildings would not enable Layer 2 connectivity across different buildings, as it would prevent the propagation of Layer 2 control traffic, such as Spanning Tree Protocol (STP) and VLAN Trunking Protocol (VTP). Combining all switches in the aggregation layer and core into a single backplane stack would not be feasible, as it would require compatible switches and sufficient stacking ports or cables, as well as create a single point of failure for the entire network. Using VRRP on the core and aggregation switches, with the aggregation switches acting as standby, would not eliminate the routing at the aggregation layer, as it would still require the aggregation switches to participate in the routing process and maintain routing tables.

References:

ArubaOS-Switch Stacking Guide

ArubaOS-Switch Virtual Switching Framework Configuration Guide

Aruba Validated Reference Design: Campus Wired LAN

This is a routed link, meaning you should only have one VLAN assigned to the link. Obvious since VLANs are terminated at a layer 3 boundary, but also right out of the curriculum.

References: The information can be referenced from the official HPE documents and learning materials available on HPE Press and Aruba Networks. Specifically, it aligns with the objectives outlined in Chapter 5: Wired Network Design, where the VSF and VLAN design considerations are discussed. Designing Aruba Solutions Official Certification Study Guide ArubaOS-Switch and ArubaOS-CX VSF Configuration Guide

Auditoriums are challenging environments for wireless design, as they often have a large number of users and devices in a relatively small area, creating high demand for bandwidth and capacity. To provide adequate RF coverage and performance, auditoriums typically require a high-density AP design, which involves deploying more APs than usual, using directional antennas, reducing transmit power, and selecting non-overlapping channels12. A high-density AP design can also help mitigate interference from other sources, such as Bluetooth devices, which operate in the 2.4 GHz band3. Auditoriums do not necessarily require the use of 80 MHz channels or DFS channels, as these options depend on the availability and regulation of the spectrum, as well as the trade-off between throughput and channel reuse . References:

1: High Density Wi-Fi Design Principles - Aruba

2: Auditorium | WBDG - Whole Building Design Guide

3: Bluetooth and Wi-Fi Coexistence Issues and Solutions for the 2.4 GHz ISM Band - Aruba

[4]: 802.11ac Channel Planning - Aruba

[5]: Dynamic Frequency Selection (DFS) - Aruba