HPE6-A47 Exam Dumps : Designing Aruba Solutions

 Aruba Instant APs are a simple, easy to deploy, and cost-effective solution for small office buildings that need wireless access. Aruba Instant APs can form a self-organizing and self-healing mesh network that supports basic rogue AP detection and provides a stateful firewall with role-based policies. Aruba Instant APs do not require a separate controller or license, and can be managed from the cloud or a mobile app. Aruba remote APs are designed for branch or home offices that need to connect to a central controller over a WAN link. Aruba campus APs and a Virtual Mobility Controller are suitable for larger or more complex deployments that need more scalability and flexibility. Aruba campus APs and an Aruba 7005 Mobility Controller are also more expensive and require additional hardware and licensing. References: Aruba Instant Access Points), Aruba Validated Design: Campus Wireless LAN)

The Virtual Switching Framework (VSF) is a technology that allows two or more Aruba switches to operate as a single logical device, providing high availability, simplified management, and increased performance. VSF is supported on Aruba 5400R zl2 switches, which are modular switches that can accommodate different types of line cards and power supplies1.

The VSF fabric requires two types of connections between the member switches: VSF links and VSF ports. VSF links are the physical connections that carry the VSF control and data traffic, while VSF ports are the logical interfaces that bundle the VSF links into a single logical link. VSF links can be either 10 GbE or 40 GbE, and VSF ports can be either 10 GbE or 40 GbE1.

To create a VSF fabric with two 5406R zl2 switches, the architect needs to ensure that the switches have the compatible modules, transceivers, and cables for the VSF links and ports. According to the ArubaOS-Switch Management and Configuration Guide1, the following requirements apply for the VSF fabric:

• The switches must have the same chassis model, the same number and type of modules, and the same firmware version.
• The switches must have at least one v3 module in slot A or B. The v3 modules are the ones with the letter “M” in the part number, such as J9990A, J9991A, and J9992A. The v2 modules are the ones with the letter “A” in the part number, such as J9534A, J9535A, and J9536A.
• The switches must have the same type of transceivers and cables for the VSF links. The supported transceivers are the Aruba 10G SFP+ LC SR, the Aruba 10G SFP+ LC LR, the Aruba 40G QSFP+ LC SR4, and the Aruba 40G QSFP+ MPO SR4. The supported cables are the Aruba 10G SFP+ to SFP+ 1m DAC Cable, the Aruba 10G SFP+ to SFP+ 3m DAC Cable, the Aruba 40G QSFP+ to QSFP+ 1m DAC Cable, and the Aruba 40G QSFP+ to QSFP+ 3m DAC Cable.

Based on the exhibit, the architect has planned to use the Aruba 40G QSFP+ to QSFP+ 1m DAC Cable (JH234A) for the VSF links, which is a supported option. However, the architect has also selected the Aruba 24p 10GBASE-T v2 zl Module (J9536A) and the Aruba 20p 10GbE SFP+ v2 zl Module (J9535A) for the switches, which are not compatible with the VSF fabric. The architect should change these v2 modules to v3 modules, such as the Aruba 24p 10GBASE-T v3 zl2 Module (J9996A) and the Aruba 20p 10GbE SFP+ v3 zl2 Module (J9990A), to meet the VSF requirements.

The other options are not issues with the plan. Adding two QSPF+ MP0 SR4 transceivers (A) is not necessary, as the DAC cable already provides the 40 GbE connection for the VSF links. Adding stacking modules and cables © is not required, as the VSF fabric does not use the traditional stacking technology. Changing the power supply type (D) is not relevant, as the VSF fabric does not impose any restrictions on the power supply type.

References: 1: ArubaOS-Switch Management and Configuration Guide - Aruba, Chapter 12: Virtual Switching Framework, pages 219-227.

 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)]