Achieve Success in the HP HPE6-A47 Exam: A Detailed Designing Aruba Solutions Guide

 References:https://www.arubanetworks.com/assets/ds/DS_7200Series.pdf

• Aruba Mobility Controller Data Sheet (Aruba Networks)
• Designing Aruba Solutions Study Guide (HPE Press)

The Aruba 2930F Switch Series is a stackable Layer 3 switch series that provides performance and ease of use for enterprises, small and medium-sized businesses, and branch office networks1. It comes with an enterprise-grade feature set that includes static and RIP routing, IPv6, ACLs, robust security, and QoS1. The 2930F Series supports more options for class-based Quality of Service (QoS) policies than the 2540 Series2. This feature is crucial for a customer who needs a wired network solution that can recognize and prioritize a wide array of different types of traffic, including casual Web browsing, voice, video, SAP Online, and file sharing.

References:

• HPE Aruba Networking 2930F Switch Series
• Why would the architect choose the 2930F rather than the 2540 Switch Series for this customer?

 The correct answer is option C, voice. Voice applications have the greatest potential impact on RF design because they are sensitive to latency, jitter, and packet loss. Voice applications also require a minimum signal strength and signal-to-noise ratio to ensure good voice quality. Therefore, an architect needs to consider the number of voice devices, the codec used, the roaming behavior, and the call admission control when planning the RF coverage for voice applications. 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 3: Wireless LAN Technologies and Standards, where the RF design considerations for voice applications are discussed. Designing Aruba Solutions Official Certification Study Guide Aruba Mobility Fundamentals Guide

The architect should propose one LIC-MM-VA-500 license package for the customer. This license package allows the customer to deploy up to two VMMs and manage up to 500 MCs and 10,000 APs. The customer does not need any additional licenses for the MCs or the APs, as they are included in the LIC-MM-VA-500 package. The other options are either insufficient or excessive for the customer’s needs.

• Option A is insufficient because six LIC-MM-VA-50 licenses only allow the customer to manage up to 300 MCs and 6,000 APs. The customer needs to manage 300 APs and six MCs, so this option does not meet the requirement.
• Option B is excessive because one LIC-MC-VA-250 and one LIC-MC-VA-50 licenses allow the customer to deploy up to 300 MCs and 6,000 APs, which is more than what the customer needs. Moreover, one LIC-MM-VA-500 license allows the customer to deploy up to two VMMs and manage up to 500 MCs and 10,000 APs, which is also more than what the customer needs. Therefore, this option is wasteful and unnecessary.
• Option D is also excessive because one LIC-MC-VA-250 and one LIC-MC-VA-50 licenses allow the customer to deploy up to 300 MCs and 6,000 APs, which is more than whatthe customer needs. Additionally, six LIC-MM-VA-500 licenses allow the customer to deploy up to 12 VMMs and manage up to 3,000 MCs and 60,000 APs, which is way more than what the customer needs. Therefore, this option is also wasteful and unnecessary.

References:

• ArubaOS 8.5 Licensing Guide)
• Aruba Mobility Master Data Sheet)
• Aruba 7000 Series Mobility Controllers Data Sheet)

The traditional guideline limits a wired VLAN to a /24 subnet, which provides enough IP addresses for 253 endpoints. You might have suggested one of three approaches: one VLAN per floor, one VLAN per building, or one VLAN per campus. The one VLAN per floor approach is not recommended because it interferes with roaming and adds complexity. If you did take this approach, the /24 subnets are not large enough for the requirements on every floor. You would need to ask for /23 subnets. The one VLAN per building approach would work if you considered each building its own RF domain. It provides roaming within a building and, if you are using a single cluster at the data center, between buildings. Ifyou deployed two MCs or clusters, one at each building, though, GRE tunneling would be required to support roaming between buildings.

Clustering is a feature that allows multiple Aruba MCs to work together as a single logical entity to provide high availability, scalability, and mobility for wireless clients12. One of the main benefits of clustering is that it provides wireless client load balancing and seamless failover for client sessions. This means that:

• Wireless clients are distributed evenly among the cluster members based on the available resources and the configured load balancing algorithm12. This helps to optimize the network performance and avoid congestion or bottlenecks.
• Wireless clients remain connected to the same MC, called the Active AP Anchor Controller (A-AAC), throughout their roaming area within the cluster, regardless of which AP they are associated with12. This ensures that the clients retain their IP address, subnet, and session information, and do not experience any disruption or delay in their connectivity or applications.
• Wireless clients can seamlessly fail over to another MC, called the Standby AP Anchor Controller (S-AAC), in case of a failure or maintenance of their A-AAC12. The S-AAC takes over the client sessions and state information from the A-AAC without requiring any re-authentication or re-association from the clients. This minimizes the impact of the failure and provides high availability and resiliency for the wireless services.

Therefore, by explaining these benefits, the architect can demonstrate how clustering can meet the customer’s high availability requirements for wireless services.

References:

• 1: https://www.arubanetworks.com/techdocs/ArubaOS_86_Web_Help/Content/arubaos-solutions/cluster/clus-over.htm
• 2: https://www.arubanetworks.com/techdocs/ArubaOS_85_Web_Help/Content/arubaos-solutions/cluster/clus-over.htm

it meets the customer’s requirements for wired network upgrade. By combining the switches in each Building 2 closet as a Virtual Switching Framework (VSF) fabric, the architect can reduce the number of logical devices within the network, simplifying management and reducing complexity, aligning with the goal of flattening architecture. Establishing two 10 GbE connections to the core per fabric ensures redundancy and resilience, maintaining connectivity even if one link fails, without necessitating additional cabling. This also provides sufficient bandwidth and scalability for the network traffic.

The other options are incorrect because:

• A. Using two additional 2930F switches to act as an aggregation layer for Building 2 adds another layer of devices and complexity to the network, contradicting the goal of flattening architecture. It also requires additional cabling and ports to connect the switches to the core and the access layer.
• B. Connecting each Building 2 switch directly to the core on a single fiber strand through the use of SFP±SR transceivers does not provide redundancy and resilience, as one link failure would disconnect the switch from the core. It also limits the bandwidth and scalability of the network, as each switch would have only one 10 GbE connection to the core.
• D. Extending additional fiber between the buildings so that each Building 2 switch can have a direct 10 GbE connection to the core requires recabling, which the customer wants to avoid. It also increases the cost and complexity of the network, as more fiber strands and ports would be needed.

References:

• Aruba 2930M Switch Series - Data sheet)
• Aruba Validated Reference Design: Campus Wired LAN - Chapter 3)
• ArubaOS-Switch Virtual Switching Framework - Configuration guide)

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

 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)]

DSCP (Differentiated Services Code Point) is a method of marking network packets with different priorities based on the type of traffic they carry. DSCP values range from 0 to 63, with higher values indicating higher priority. DSCP values are typically mapped to one of the four WMM (Wi-Fi Multimedia) queues, which are used to prioritize wireless traffic on the access points and controllers. WMM queues are: voice, video, best effort, and background12.

The default QoS settings for Aruba APs and controllers map the DSCP values to the WMM queues as follows3:

Table

DSCP Value

WMM Queue

0-7

Background

8-23

Best Effort

24-39

Video

40-63

Voice

According to these settings, the DSCP values 46 and 34, which are assigned to voice and video traffic by Windows policies, will both be mapped to the video WMM queue. This means that both types of traffic will receive the same priority, and voice traffic will not receive the highest priority that it should. This can result in poor voice quality, increased latency, jitter, or packet loss, especially when the network is congested or bandwidth is limited. Voice traffic is more sensitive to these factors than video traffic, and requires strict QoS to ensure optimal performance and user experience4.

To avoid this potential issue, the architect should explain to the customer that they need to modify the QoS settings on the Aruba APs and controllers to match the DSCP values assigned by Windows policies. This can be done by using the following commands on the Aruba controller3:

(config) #wmm traffic-management-profile voice

(config) #dscp 46

(config) #wmm traffic-management-profile video

(config) #dscp 34

These commands will map the DSCP value 46 to the voice WMM queue, and the DSCP value 34 to the video WMM queue, ensuring that voice traffic receives the highest priority and video traffic receives the second highest priority. This will improve the QoS for the Skype for Business UC solution and enhance the end-user experience.

References:

• 1: https://www.arubanetworks.com/techdocs/ArubaOS_86_Web_Help/Content/arubaos-solutions/1-overview/qos.htm
• 2: https://www.arubanetworks.com/techdocs/ArubaOS_86_Web_Help/Content/arubaos-solutions/1-overview/wmm.htm
• 3: https://www.arubanetworks.com/techdocs/ArubaOS_86_Web_Help/Content/arubaos-solutions/1-overview/qos-mapping.htm
• 4: https://www.arubanetworks.com/techdocs/ArubaOS_86_Web_Help/Content/arubaos-solutions/1-overview/qos-voice.htm