HPE3-U01 Aruba Certified Network Technician Exam (ACNT) Questions and Answers

The IP address 10.0.128.0/23 is a Class A private address with a subnet mask of 255.255.254.0. This means that the network prefix is 10.0.128.0 and the host identifier is the last 9 bits of the address. To find the number of IP assignable addresses, we need to subtract 2 from the total number of possible hosts, which is 29 = 512 . This is because the network address (10.0.128.0) and the broadcast address (10.0.129.255) are reserved and cannot be assigned to any host. Therefore, the number of IP assignable addresses is 512 - 2 = 510. References: IP Subnet Calculator , CIDR Calculator for IPv4 addresses , Free online IPv4 subnet calculator

Layer 2 encapsulation is the process of adding a header and a trailer to the data coming from the upper layer (Layer 3) before sending it over the physical medium. The header and the trailer contain information such as source and destination MAC addresses, error detection, and protocol type. The devices that perform Layer 2 encapsulation are usually switches, bridges, or network interface cards (NICs). In the given network diagram, the PC is sending a message to the server. The PC first adds a Layer 2 header and trailer to the data and sends it to Switch-1. Switch-1 performs Layer 2 encapsulation again before forwarding it to the router. The router operates at Layer 3 and does not perform Layer 2 encapsulation. It only removes the Layer 2 header and trailer, checks the destination IP address, and forwards the packet to the next hop. The packet then reaches Switch-2, where Layer 2 encapsulation occurs again before it is sent to the server. The server also performs Layer 2 de-encapsulation by removing the header and trailer and passing the data to the upper layer. Therefore, the devices that have performed Layer 2 encapsulation by the time the message arrives at the server are Switch-1 and Switch-2.  References:   Understanding Data Link Layer Encapsulation ,  How Data Encapsulation & De-encapsulation Works? ,  HDLC Protocol and Encapsulation method Explained

A hardwire desktop PC belongs to the category of stationary devices, which are devices that are fixed in one location and do not move. Stationary devices typically have a constant power supply and a wired network connection. Examples of stationary devices are desktop PCs, servers, printers, and IP phones. Stationary devices are different from mobile devices, which are devices that can move from one location to another and connect to the network wirelessly. Mobile devices can be further classified into somewhat mobile devices, highly mobile devices, and intermittent mobile devices, depending on their mobility patterns and network requirements. Examples of mobile devices are laptops, tablets, smartphones, and wearable devices.  References:

Aruba Certified Network Technician (ACNT) | HPE Aruba Networking

Aruba Documentation Portal

 Wi-Fi is a wireless networking protocol that uses radio waves to communicate data over the air. Radio waves are electromagnetic waves that have different characteristics depending on their amplitude, phase, and frequency. Amplitude is the height of the wave, phase is the position of the wave relative to a reference point, and frequency is the number of cycles of the wave per second. To transmit data using Wi-Fi, these characteristics are modulated, or changed, according to a predefined scheme that encodes bits of information. For example, a high amplitude wave can represent a 1 bit, and a low amplitude wave can represent a 0 bit. Similarly, a positive phase shift can represent a 1 bit, and a negative phase shift can represent a 0 bit. Likewise, a high frequency wave can represent a 1 bit, and a low frequency wave can represent a 0 bit. By modulating these characteristics, Wi-Fi can transmit data in binary form over the air. Different modulation schemes can achieve different data rates and reliability, depending on the channel conditions and interference. Some common modulation schemes used by Wi-Fi are Binary Phase Shift Keying (BPSK), Quadrature Phase Shift Keying (QPSK), Quadrature Amplitude Modulation (QAM), and Orthogonal Frequency Division Multiplexing (OFDM).  References:   Understanding Wi-Fi and How It Works ,  Introduction to Wi-Fi Wireless Networking ,  Wireless Communication - Overview ,  Wireless Communication | Set 1 .

 Aruba Central is a cloud-based networking solution that offers simplicity, security, and scalability for managing Aruba network infrastructure. It uses HTTPs to communicate with networking equipment such as wireless, wired, VPN, and SD-WAN devices. It also provides AI-powered insights, workflow automation, and advanced security features to unify operations across campus, branch, data center, and remote work environments. Aruba Central does not require an on-premises server, nor does it use SNMP for management. It also does not support third-party networking equipment, as it is designed for Aruba ESP (Edge Services Platform).  References:   Aruba Central for Cloud-managed networking ,  About Aruba Central ,  Aruba Central data sheet

 The 5 GHz band is a radio frequency band used for Wi-Fi communications. It has a higher data bandwidth than the 2.4 GHz band, but a shorter range and less penetration through walls. The 5 GHz band is divided into several sub-bands, each with a different set of channels. One of these sub-bands is the U-NII-3 band, which covers the frequency range from 5725 MHz to 5850 MHz. This sub-band contains 24 non-overlapping channels, numbered from 149 to 172. Channels 149 to 161 are part of the 5 GHz band and can be used for Wi-Fi communications. Channels 165 and 169 are restricted to indoor use only, and channel 173 is not allowed in some regions. Channels 12, 13, and 14 are not part of the 5 GHz band, but belong to the 2.4 GHz band, which has a different set of channels and regulations. U-NII-5 is not a valid sub-band name, but a proposed extension of the 5 GHz band to include the frequency range from 5925 MHz to 7125 MHz. This extension is not yet approved or implemented, and therefore not part of the 5 GHz band.  References:   List of WLAN channels ,  What’s the Difference Between 2.4 and 5 GHz Wi-Fi (and Which Should I Use)? ,  What is the difference between 2.4 GHz, 5 GHz, and 6 GHz wireless frequencies?

The command to access the second interface of the third slot in a modular ArubaOS-CX switch is  interface 1/3/2 .  This is because the interface numbering format for modular switches is  interface slot/module/port , where slot is the chassis slot number, module is the module number within the slot, and port is the port number within the module 1 .  The slot number starts from 1, the module number starts from 0, and the port number starts from 1 2 . Therefore, the second interface of the third slot is  interface 1/3/2 . The other options are incorrect because they do not follow the correct interface numbering format.  References:   AOS-CX 10.06 Command-Line Interface Guide 8320, 8

Role Based controls are a feature of Aruba Central that allows you to assign different access privileges and policies to different groups of users on a WLAN network. You can set the Role Based controls in the Security section of the Aruba Central WLAN configuration Wizard. In this section, you can configure the following parameters:

Authentication Type: The method of verifying the identity of users who connect to the WLAN network. You can choose from several options, such as WPA2-Enterprise, WPA2-Personal, Captive Portal, MAC Authentication, or Open.

Authentication Server: The server that performs the authentication process for the users. You can select an existing server from the list, or create a new one by clicking the + icon. You can also configure the server settings, such as IP address, port, shared secret, and timeout.

User Role Assignment: The method of assigning user roles to the authenticated users. You can choose from several options, such as Default Role, Role Derivation, or Server Group Role. A user role is a set of firewall policies and VLAN settings that define the access privileges and restrictions for a group of users.

Default User Role: The user role that is assigned to the users by default, if no other role assignment method is selected. You can select an existing user role from the list, or create a new one by clicking the + icon. You can also configure the user role settings, such as firewall policies, VLAN ID, and bandwidth limit.

References:

Configuring Security Settings for Wireless Network

Basic WLAN Configuration Workflow

 Unicast is a type of data transmission where a message is sent from one sender to one receiver, each identified by a network address. Unicast is a one-to-one communication, as opposed to broadcast and multicast, which are one-to-many communications. Unicast is typically used for real-time data streams, such as video, audio, or online presentations, that are shared with a single user over the Internet. Unicast can also be used for email, file transfer, and other applications that require a specific recipient.  References:   Unicast - Wikipedia ,  Difference between Unicast, Broadcast and Multicast in Computer Network - GeeksforGeeks ,  Unicast Definition - TechTerms.com

The subnet mask 255.255.252.0 is equivalent to the CIDR notation /22, which means that 22 bits are used for the network prefix and 10 bits are used for the host part. To calculate the number of addresses that this subnet mask provides, we can use the formula 2n − 2 , where n is the number of bits in the host part. In this case, n = 10 , so the number of addresses is 210 − 2 = 1024 − 2 = 1022 . The subtraction of 2 is because the first and the last addresses are reserved for the network identifier and the broadcast address, respectively. Therefore, the subnet mask 255.255.252.0 provides 1022 usable addresses for hosts, plus 2 reserved addresses, for a total of 1024 addresses. References: IP Subnet Calculator , How many host addresses are available on the network … - ITExamAnswers

The OSI model is a conceptual framework that describes the process of transmitting data between computers. It is divided into seven layers, each with a specific function. The application layer, or layer 7, is the highest layer of the OSI model and is responsible for creating data. The application layer provides services such as resource sharing, remote file access, email, web browsing, etc. The data created by the application layer is then passed down to the presentation layer, which translates it into a common format for the lower layers.  The data is then further processed by the session, transport, network, data link, and physical layers until it reaches the destination 1 2   References:

What is OSI Model | 7 Layers Explained

OSI model - Wikipedia

According to the Aruba Network Technician (ACNT) documents and learning resources, the valid configurable “Client VLAN Assignment” options for a Bridge-based WLAN in Aruba Central are native VLAN, automatic VLAN, and static VLAN. These options allow you to specify how the VLAN ID for the WLAN clients is determined.

Native VLAN: This option allows you to use the native VLAN of the AP’s Ethernet port as the VLAN ID for the WLAN clients. The native VLAN is the default VLAN that carries untagged traffic on a trunk port. This option is useful when you want to simplify the VLAN configuration and use the same VLAN for all the WLAN clients connected to the same AP.

Automatic VLAN: This option allows you to use the VLAN ID assigned by a DHCP server to the WLAN clients. The DHCP server can use attributes such as MAC address, hostname, or vendor class to assign different VLAN IDs to different WLAN clients. This option is useful when you want to dynamically assign VLANs based on the client characteristics or policies.

Static VLAN: This option allows you to specify a single VLAN ID for all the WLAN clients. You can either enter a VLAN ID manually or select a named VLAN from the drop-down list. A named VLAN is a VLAN that has a user-defined name associated with it for easy identification. This option is useful when you want to assign a fixed VLAN to a WLAN SSID.

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Ethernet is a protocol that provides frame delivery using physical addressing and error detection using frame check sequence. Ethernet frames have a source and destination MAC address that identify the physical devices on the network. Ethernet frames also have a frame check sequence (FCS) field that uses a cyclic redundancy check (CRC) to detect errors in the frame. If the receiver calculates a different FCS value than the one in the frame, it discards the frame and may request a retransmission. Link Layer Discovery Protocol (LLDP) is a protocol that allows devices to discover and advertise information about themselves and their neighbors. TCP/IP is a suite of protocols that operate at the network and transport layers, not the data link layer. User Datagram Protocol (UDP) is a transport layer protocol that provides connectionless and unreliable data delivery, without error detection or correction.  References:   Ethernet Frame Format - Aruba ,  Frame check sequence - Wikipedia

 A collision occurs when two or more devices try to transmit data at the same time on a shared medium, such as a cable or a wireless channel. Collisions result in corrupted or lost data, and reduce the efficiency of the network. Different connection types have different susceptibility to collisions, depending on how they handle data transmission and collision detection.

Dark fiber and fiber are optical connections that use light to transmit data. They are immune to electromagnetic interference and have very high bandwidth. They also use full-duplex communication, which means that data can be sent and received simultaneously on separate fibers. Therefore, collisions are very unlikely to happen on dark fiber and fiber connections.

Copper is an electrical connection that uses metal wires to transmit data. It is prone to electromagnetic interference and has lower bandwidth than optical connections. It can use either half-duplex or full-duplex communication, depending on the device and the protocol. Half-duplex communication means that data can only be sent or received at a time on the same wire. Therefore, collisions are more likely to happen on copper connections that use half-duplex communication, such as Ethernet hubs.

Wi-Fi is a wireless connection that uses radio waves to transmit data. It is also prone to electromagnetic interference and has lower bandwidth than optical connections. It uses half-duplex communication, which means that data can only be sent or received at a time on the same channel. Therefore, collisions are very likely to happen on Wi-Fi connections, especially when there are many devices using the same channel or frequency.

References:

Types of Collisions

What are elastic and inelastic collisions?

Why is a switch port a collision domain?

 Switches and routers are both networking devices that operate at different layers of the OSI model and perform different functions. The key differences between L2 switches and routers are:

Switches operate at the data link layer (Layer 2) of the OSI model, while routers operate at the network layer (Layer 3). This means that switches forward frames based on the MAC addresses of the source and destination devices, while routers route packets based on the IP addresses of the source and destination networks.

Switches build a MAC table that maps MAC addresses to switch ports, while routers build a routing table that maps IP addresses to next-hop interfaces. The MAC table is used by switches to determine which port to send a frame to, while the routing table is used by routers to determine which interface to send a packet to.

Switches offer a considerably higher port density than routers, meaning that they can connect more devices to the network. Switches typically have dozens or hundreds of Ethernet ports, while routers usually have a few Ethernet ports and other types of ports such as ADSL, cable, fiber, dial-up, etc. Switches are used to create LAN segments, while routers are used to connect different networks or subnets.

Switches are faster than routers because they do not take up time looking at the network layer header information. Switches can forward frames at wire speed, while routers need to process packets at the network layer and perform additional functions such as NAT, firewall, QoS, etc.

References:   Switch (L2/L3) Vs Router: Comparison and Differences in TCP/IP Networks ,  Key Differences Between Routers and Different Types of Switches ,  Layer 2 Switch - How it operates, when to use it - Network Encyclopedia ,  Layer 2 switching - Study-CCNA ,  Differences Between Layer 2 and Layer 3 Switches ｜ Which one do you need ？