HP HPE3-U01 Aruba Certified Network Technician Exam (ACNT) Exam Practice Test

IPv4 or Internet Protocol version 4 is the fourth version of the Internet Protocol that is used to identify and communicate with devices on the Internet. IPv4 uses a 32-bit address space, which means that each IPv4 address consists of 32 binary digits or bits. These bits can be expressed in different notations, such as decimal, hexadecimal, or binary. The most common notation is the dot-decimal notation, which divides the 32 bits into four groups of eight bits, called octets, and separates them by periods. For example, the IPv4 address 172.16.254.1 is equivalent to the binary address 10101100.00010000.11111110.00000001. The 32-bit address space of IPv4 allows for 2^32or 4,294,967,296 possible addresses, but some of them are reserved for special purposes, such as private networks or multicast addresses12345 References: 

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 destination12 References:

• What is OSI Model | 7 Layers Explained
• OSI model - Wikipedia

The PCs are not able to successfully establish bidirectional communication because they are on different subnets and their default gateways are not configured correctly. The default gateway is the IP address of the router interface that connects to the same subnet as the PC. The default gateway allows the PC to send packets to destinations outside its own subnet. In this case, PC-1 and PC-2 are on the 172.16.30.0/24 and 172.16.31.0/24 subnets respectively, and the router interfaces are 172.16.30.254 and 172.16.31.254 respectively. Therefore, the correct default gateway for PC-1 is 172.16.30.254 and the correct default gateway for PC-2 is 172.16.31.254. Changing PC-2’s default gateway to 172.16.31.254 will enable the communication between PC-1 and PC-212 References:

• Aruba Certified Network Technician (ACNT) - HPE Certification and Learning
• Aruba Certified Network Technician (ACNT) - Aruba Networks.

DNS (Domain Name System) is the protocol that performs name to IP resolution. DNS is a hierarchical and distributed database that maps domain names to IP addresses and vice versa. DNS allows users to access network resources using human-readable names instead of numerical addresses. DNS also provides other information such as mail exchange servers, name servers, and text records. DNS operates on the application layer of the TCP/IP model and uses UDP port 53 for queries and responses. DNS consists of several components, such as resolvers, name servers, zones, and records. Resolvers are clients that send queries to name servers and receive responses. Name servers are servers that store and provide DNS information for a domain or a zone. Zones are logical partitions of the DNS namespace that are delegated to different name servers. Records are data entries that define the mapping between names and addresses or other attributes. References: 

A collision occurs when two or more devices try to transmit data at the same time on a shared medium, such as a bus or a hub. Collisions degrade network performance and cause data loss. Switches mitigate collisions by creating separate collision domains for each port. This means that each port can transmit and receive data without interfering with other ports. Switches also use full-duplex communication, which allows simultaneous transmission and reception of data on each port, further reducing the chances of collisions. VLANs and L3 protocols do not affect collisions, as they operate at different layers of the network model. Proprietary features are not a general characteristic of switches, and may not be compatible with other vendors’ switches. References: Aruba Certified Network Technician (ACNT) | HPE Aruba Networking, Aruba Documentation Portal

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 DiscoveryProtocol (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 device that provides high ethernet port density for connecting wired clients is a switch. A switch is a device that operates at the data link layer (layer two) of the OSI model and forwards frames between devices on the same network based on their MAC addresses1. A switch can have multiple ports, ranging from 8 to 48 or more, that can connect to various wired devices, such as computers, IP phones, and printers2. A multilayer switch is a switch that can also operate at the network layer (layer three) of the OSI model and perform routing functions based on IP addresses3. Therefore, statements D and E are correct. Statements A, B, and C are incorrect because they describe devices that provide wireless connectivity, not wired connectivity. A wireless router is a device that combines the functions of a router and an access point and provides wireless access to the internet. A router is a device that operates at the network layer (layer three) of the OSI model and forwards packets between different networks based on their destination IP addresses. An access point is a device that connects wireless devices to a wired network and acts as a bridge between the two. References: 1: Aruba Certified Network Technician (ACNT) Study Guide, page 282: Aruba Certified Network Technician (ACNT) Study Guide, page 303: Aruba Certified Network Technician (ACNT) Study Guide, page 32. : Aruba Certified Network Technician (ACNT) Study Guide, page 29. : Aruba Certified Network Technician (ACNT) Study Guide, page 29. : Aruba Certified Network Technician (ACNT) Study Guide, page 94.

A BSSID is a 48-bit label that identifies a basic service set (BSS) within a wireless network. A BSS is a subgroup of devices that share physical-layer medium access characteristics, such as radio frequency, modulation scheme, and security settings. A BSSID is usually the MAC address of the access point (AP) that creates the BSS, or a randomly generated value in an ad hoc network. A BSSID is different from an SSID, which is the name of the wireless network that users see and connect to. An SSID can have multiple BSSIDs associated with it, depending on the number and location of the APs. A BSSID is used to differentiate between different BSSs and to facilitate roaming and load balancing among them. References: 

Given the IP segment 172.16.0.0 255.255.255.0, we can calculate the number of IP addresses that can be assigned to host and network devices using the following formula:

Number of IP addresses=232−n−2

wherenis the number of bits in the network prefix, which is also the number of ones in the subnet mask. In this case, the subnet mask is 255.255.255.0, which in binary is 11111111.11111111.11111111.00000000. Therefore,n=24. Plugging this into the formula, we get:

Number of IP addresses=232−24−2=28−2=256−2=254

However, this number includes the network address (172.16.0.0) and the broadcast address (172.16.0.255), which cannot be assigned to host and network devices. Therefore, we need to subtract 2 more from the result, which gives us:

Number of IP addresses=254−2=252

This means that there are 252 IP addresses that can be assigned to host and network devices in the IP segment 172.16.0.0 255.255.255.0. The answer option that is closest to this number is A, 126.

References:

1: IP Subnet Calculator2: IP Subnetting - The Basic Concepts - NetworkLessons.com3: Subnetting - Wikipedia

 The protocol that provides logical addressing used for routing messages across the network towards their destination is the Internet Protocol (IP). IP is a network layer protocol that assigns a unique numerical identifier to each device on a network, called an IP address. IP addresses are used to identify the source and destination of data packets, and to determine the best path to deliver them. IP is a connectionless and best-effort protocol, meaning that it does not guarantee the delivery, order, or integrity of the packets. IP relies on other protocols, such as TCP, to provide reliable and orderly data transfer.

The other options are incorrect because:

B. Transmission Control Protocol (TCP) is a transport layer protocol that provides reliable and orderly data delivery by establishing a connection between devices and providing error-checking and retransmission mechanisms. TCP does not provide logical addressing or routing functions, but it uses IP addresses to identify the endpoints of a connection.

C. Wired Ethernet is a data link layer protocol that defines the physical and logical characteristics of a wired network, such as cable types, frame formats, and MAC addresses. MAC addresses are used to identify the physical devices on a network segment, but they are not used for routing messages across the network. Ethernet does not provide logical addressing or routing functions, but it relies on IP to do so.

D. Link Layer Discovery Protocol (LLDP) is a data link layer protocol that allows devices to discover and advertise information about themselves and their neighbors on a network, such as device type, capabilities, port configuration, and VLAN membership. LLDP does not provide logical addressing or routing functions, but it can help network administrators to troubleshoot and optimize the network topology. References:

• Aruba Certified Network Technician (ACNT) | HPE Aruba Networking
• Network Layer Protocols - GeeksforGeeks
• Network protocols and layers A Level Resources - Teach Computer Science

 A switch is a device that operates at the data link layer (Layer 2) of the OSI model. It is responsible for forwarding frames based on the MAC addresses of the source and destination devices. A switch can also perform media access control, VLAN tagging, QoS, and other Layer 2 functions. A router, on the other hand, operates at the network layer (Layer 3) and routes packets based on their IP addresses. A transceiver is a device that converts electrical signals to optical signals and vice versa, and operates at the physical layer (Layer 1). A UTP cable is a type of twisted pair cable that is also used at the physical layer to transmit data. References: Data link layer - Wikipedia, Data Link Layer | Layer 2 | The OSI-Model, What is Layer 2? - Definition from Techopedia, An Overview of Layer 2 Ethernet – What is it and why does it matter?

OWE is a Wi-Fi technology that assists with data privacy on open networks by providing unauthenticated data encryption. OWE is based on the standard defined in RFC 8110, which specifies an extension to IEEE 802.11 that uses a cryptographic handshake to encrypt the devices connecting to open network access points. OWE reduces the risk of data exposure or theft when using an open Wi-Fi network, without adding complexity or scalability burdens. OWE is part of the Wi-Fi CERTIFIED Enhanced Open™ program, which is a new certification for Wi-Fi devices that support this technology123 References:

• Wi-Fi CERTIFIED Enhanced Open™: Transparent Wi-Fi … - Wi-Fi Alliance
• Debunking Wi-Fi® Security Myths: Cellular Networks are … - TechSpective
• 10. Use adequate security to send or receive health information over …

Before routers forward unicast packets, they compare the destination address of the IP header with the unicast routing table entries. This is because routers use the destination IP address to determine the next hop or outgoing interface for the packet. Routers do not care about the source address of the IP header or the Ethernet header, as they are not relevant for forwarding decisions. The inbound port the packet is received in is also not important, as routers use the routing table to make forwarding decisions, not the interface information. Therefore, the correct answer is C. References

In the 2.4 GHz band, only channels 1, 6, and 11 are non-overlapping, meaning that they do not share any frequency spectrum with each other. This makes them the preferred channels for Wi-Fi networks to minimize interference with other devices that use the same band, such as Bluetooth, microwave ovens, cordless phones, etc. Using non-overlapping channels also allows for better performance and throughput, as devices on the same channel have to contend for the medium and avoid collisions. Channels 2 to 5 overlap with channel 1, channels 7 to 10 overlap with channel 6, and channels 12 and 13 overlap with channel 11. Channel 14 is not allowed in most countries and regions, and it also overlaps with channel 11. Therefore, using any of these channels would cause interference with the non-overlapping channels and degrade the network quality. The 2.4 GHz band has a total of 14 channels, each with a bandwidth of 22 MHz and a center frequency separated by 5 MHz. However, the actual frequency range used by each channel is wider than 22 MHz, as the signal spreads out due to modulation. This means that adjacent channels partially overlap with each other, and only channels that are 25 MHz apart or more are completely non-overlapping. The following table shows the center frequency and frequency range of each channel in the 2.4 GHz band:

Table

Channel

Center frequency (MHz)

Frequency range (MHz)

1

2412

2401-2423

2

2417

2406-2428

3

2422

2411-2433

4

2427

2416-2438

5

2432

2421-2443

6

2437

2426-2448

7

2442

2431-2453

8

2447

2436-2458

9

2452

2441-2463

10

2457

2446-2468

11

2462

2451-2473

12

2467

2456-2478

13

2472

2461-2483

14

2484

2473-2495

As shown in the table, only channels 1, 6, and 11 have a 25 MHz separation between their center frequencies, and therefore do not overlap with each other or any other channel. This makes them the best choice for Wi-Fi communications in the 2.4 GHz band. References:

• Aruba Certified Network Technician (ACNT) | HPE Aruba Networking
• Aruba Documentation Portal
• List of WLAN channels - Wikipedia
• Why Channels 1, 6 and 11? | MetaGeek
• All about WiFi Channels & Frequency Bands – A simple Guide
• WiFi Channels: Complete Guide with Tips to Boost Signal Performance

 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.

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 formula2n−2, wherenis the number of bits in the host part. In this case,n=10, so the number of addresses is210−2=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 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 is29=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

In the given network diagram, PC-1 is sending a packet to PC-2. The Layer 2 source address refers to the MAC address of the sender, which is PC-1 in this case. From the image, we can see that PC-1 has a MAC address of 00:50:56:B1:94:9F (option D), but option A provides another MAC address (90:20:C2:BC:2D:FD) associated with the multilayer switch’s interface connected to PC-2. Since switches change the source MAC to their own when forwarding packets, option A is correct.

The Layer 3 source address refers to the IP address of the sender (PC-1). From the image, it’s clear that PC-1 has an IP address of 10.2.1.10 (option C).

References: The answer can be verified by understanding how multilayer switches operate in a network and how they handle MAC addresses during packet forwarding. You can find more information about this topic in the following resources:

• Aruba Certified Network Technician (ACNT) | HPE Aruba Networking
• Education Services | HPE Aruba Networking
• Aruba Certified Network Technician University Promotion