Cisco 200-301 Cisco Certified Network Associate (CCNA) Exam Dumps and Practice Test Questions Set 2 Q16-30

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Question 16

Which layer of the OSI model is responsible for establishing, managing, and terminating sessions between applications?

A) Session
B) Transport
C) Presentation
D) Network

Answer: A) Session

Explanation

The Session layer is a crucial component of the OSI (Open Systems Interconnection) model, responsible for managing communication sessions between applications on different devices. A session represents an ongoing exchange of information between two systems, and the Session layer ensures that this exchange occurs in a controlled and organized manner. Its primary responsibilities include establishing, maintaining, and terminating sessions, allowing applications to communicate reliably without data loss or confusion. By providing this functionality, the Session layer facilitates structured communication, enabling devices to coordinate interactions efficiently over a network.

One of the key functions of the Session layer is session establishment. Before data can be exchanged, the Session layer sets up a session between the two communicating applications. This setup ensures that both sides are ready to send and receive information and agree on the communication parameters, such as session identifiers and dialog control methods. The layer can manage different types of dialog modes, including half-duplex, where communication occurs in one direction at a time, and full-duplex, where data can flow simultaneously in both directions. This flexibility ensures that applications can operate according to their specific communication needs.

Once a session is established, the Session layer maintains the connection by managing data exchange in an orderly manner. It can implement checkpoints or synchronization points that allow the session to recover gracefully in case of interruptions or failures. For instance, if a network disruption occurs during a file transfer, the Session layer can ensure that only the affected portion of the data needs to be retransmitted, rather than restarting the entire transfer. This capability enhances reliability and reduces the risk of data loss during communication, making it particularly valuable for applications that require continuous, real-time interactions, such as video conferencing or database transactions.

It is important to distinguish the Session layer from other layers in the OSI model, as they provide complementary but different functions. The Transport layer, for example, is responsible for ensuring end-to-end delivery of data segments, providing error detection and correction, and guaranteeing that data arrives intact and in order. However, it does not manage the setup, maintenance, or termination of sessions. Its primary focus is reliable data transport rather than coordinating the communication session itself.

The Presentation layer handles data formatting, encryption, and compression to ensure that information can be interpreted correctly by the application layer. While it prepares and translates data for application use, it does not establish or manage sessions between applications. Similarly, the Network layer is responsible for logical addressing and routing, determining the most efficient path for packets to travel across multiple networks. Although critical for connectivity, it does not handle session control or coordination.

Given that the requirement is to manage sessions—including initiation, maintenance, and termination—the Session layer is the most appropriate choice. It provides structured communication, dialog control, synchronization, and recovery mechanisms, enabling applications on different devices to communicate effectively. By coordinating these activities, the Session layer ensures that data exchange is organized, reliable, and resilient, supporting a wide range of networked applications and services.

Question 17

Which command is used to view the current interface IP configuration on a Cisco device?

A) show ip interface brief
B) show running-config
C) show vlan brief
D) show startup-config

Answer: A) show ip interface brief

Explanation

The show ip interface brief command is an essential tool for network administrators managing Cisco devices, such as routers and switches. This command provides a concise summary of all interfaces on a device, including critical information such as the assigned IP addresses, the operational status of each interface, and the status of the line protocol. By displaying this information in a brief and organized format, it allows administrators to quickly verify which interfaces are active, which have been assigned IP addresses, and whether the interfaces are up or down. This overview is particularly valuable for troubleshooting connectivity issues or confirming interface configurations during network setup or maintenance.

One of the primary advantages of the show ip interface brief command is its ability to present the operational state of interfaces in real-time. For example, it shows whether an interface is administratively up or down and whether the line protocol is operational. This distinction is important because an interface may be configured with an IP address but could still be inactive due to a shutdown command or physical connectivity problem. By providing both configuration and status information in a single, easy-to-read output, show ip interface brief helps administrators quickly identify interfaces that require attention or corrective action.

Other Cisco commands provide related information, but none are as efficient for quickly verifying interface status and IP configuration. The show running-config command displays the full current configuration stored in memory, including all interface settings, routing configurations, and other device parameters. While this command contains interface IP addresses and configuration details, the output is lengthy and less focused, making it less convenient for a rapid overview of interface status. Administrators may need to scroll through extensive configuration data to locate relevant information, which can slow down troubleshooting and verification processes.

The show vlan brief command is useful for managing VLANs on switches. It provides information about configured VLANs and the ports assigned to each VLAN, allowing administrators to verify VLAN membership and connectivity. However, this command does not display IP addresses or the operational state of interfaces, so it cannot be used to confirm whether a specific interface is active or properly configured with an IP address.

The show startup-config command displays the configuration saved in non-volatile memory (NVRAM). While it reflects the intended configuration that will be loaded on device reboot, it does not show real-time operational status. An interface could be configured in the startup configuration but may be administratively down, disconnected, or otherwise inactive at the moment, so this command cannot confirm current interface operability.

Because the requirement is to view the current IP configuration and real-time status of interfaces, show ip interface brief is the most appropriate choice. It combines concise output, visibility of IP addresses, and operational status, enabling administrators to quickly assess the state of all interfaces and troubleshoot connectivity issues efficiently. Its clear, focused format makes it an indispensable tool for network management and verification tasks, allowing network engineers to maintain operational awareness of devices without navigating through lengthy configuration files or unrelated command outputs.

Question 18

Which device is primarily used to connect different networks and route packets based on IP addresses?

A) Router
B) Switch
C) Hub
D) Access Point

Answer: A) Router

Explanation

Routers are essential networking devices that operate primarily at the Network layer of the OSI model. Their main function is to connect multiple networks and direct data packets between them based on logical IP addresses. Routers are responsible for determining the most efficient path for data to travel from a source device to a destination device, whether those devices are on the same local network or located across different subnets or geographic locations. They achieve this by maintaining routing tables and using routing protocols such as OSPF, EIGRP, or BGP to dynamically update information about network topology and select optimal paths for packet delivery. This ability to make intelligent forwarding decisions based on IP addresses allows routers to manage traffic between networks effectively, ensuring that data reaches its intended destination efficiently and reliably.

One of the key features of routers is their capacity to segment networks. By creating separate broadcast domains, routers prevent unnecessary traffic from propagating across the entire network, which enhances performance and security. For example, a corporate network might consist of multiple subnets for different departments. A router connecting these subnets ensures that traffic intended for a specific subnet is routed correctly without overwhelming devices in other subnets. Additionally, routers can implement policies such as access control lists (ACLs) to filter traffic based on IP addresses, adding an extra layer of network security.

Other network devices, while important for connectivity, serve different purposes and do not perform routing functions. Switches operate at the Data Link layer and forward frames based on MAC addresses. They primarily function within a single network segment, connecting multiple devices to form a local area network (LAN). While switches can intelligently forward frames to specific devices, they do not examine IP addresses or route traffic between different networks.

Hubs, which operate at the Physical layer, are even simpler devices. They broadcast incoming signals to all connected ports without any form of intelligent traffic management. Because they do not process data at the Network or Data Link layers, hubs cannot route packets or manage network segmentation, making them inefficient for modern networking needs.

Access points provide wireless connectivity for devices, allowing laptops, smartphones, and other devices to connect to a network without cables. While they operate at the Data Link and Physical layers, access points do not make routing decisions or manage traffic between different IP networks. Their primary role is to extend network access wirelessly rather than to perform intelligent packet forwarding.

Given that the primary goal is to route packets between different networks based on IP addresses, a router is the most appropriate device. It operates at the Network layer, examines destination IP information, and uses routing tables and protocols to determine the optimal path for each packet. Routers enable inter-network communication, enforce network policies, segment broadcast domains, and ensure efficient and reliable delivery of data across complex network architectures. Without routers, devices on different networks would be unable to communicate effectively, making them indispensable components in both local and wide-area networking environments.

Question 19

Which protocol is used to resolve MAC addresses for a known IPv4 address?

A) ARP
B) DNS
C) DHCP
D) ICMP

Answer: A) ARP

Explanation

Address Resolution Protocol, commonly known as ARP, is a fundamental network protocol used to map IPv4 addresses to their corresponding Media Access Control (MAC) addresses within a local area network. In Ethernet-based networks, communication between devices at the data link layer relies on MAC addresses, which uniquely identify network interface cards. However, most higher-level network operations, including IP-based routing and communication, use IP addresses. ARP bridges the gap between these two addressing schemes by translating an IP address into a MAC address, enabling devices to send frames directly to the correct physical hardware on the same subnet.

When a device needs to communicate with another device on the same local network but only knows its IP address, it broadcasts an ARP request. This request asks, “Who has this IP address?” The device that owns the specified IP address responds with an ARP reply, providing its MAC address. Once the requesting device receives this reply, it can encapsulate data into Ethernet frames addressed to the target MAC address and transmit the data successfully. This process occurs automatically and transparently to the user, allowing seamless communication between devices without requiring manual address mapping. Additionally, devices typically cache ARP responses in an ARP table or cache, which reduces the need for repeated broadcasts and improves network efficiency.

It is important to distinguish ARP from other networking protocols that serve different purposes. The Domain Name System, or DNS, is designed to resolve human-readable hostnames into IP addresses. While DNS translates names like www.example.com into an IP address usable for routing, it does not provide any mechanism to determine the MAC address associated with that IP address. Therefore, DNS is not involved in data link layer communication and cannot fulfill the role of IP-to-MAC resolution.

Dynamic Host Configuration Protocol, or DHCP, assigns IP addresses to hosts dynamically within a network. While DHCP facilitates the allocation of IP addresses to devices, it does not map those addresses to MAC addresses for communication purposes. DHCP ensures that devices obtain valid network configurations, such as IP address, subnet mask, default gateway, and DNS server information, but it does not assist in the data link layer delivery of packets.

Internet Control Message Protocol, or ICMP, is another commonly used protocol, primarily for diagnostic and error-reporting purposes. ICMP allows devices to send messages like echo requests and replies, commonly used by the ping command to verify network reachability. While ICMP helps in troubleshooting and monitoring network connectivity, it does not provide the functionality of resolving IP addresses into hardware addresses necessary for local network communication.

Given the need to map an IPv4 address to a MAC address within a local subnet, ARP is the correct protocol. It directly enables devices to communicate at the data link layer by resolving IP addresses into physical hardware addresses. Without ARP, IP-based communication on a local network would fail because devices would not know how to address Ethernet frames to the correct destination. By providing this essential translation function, ARP ensures efficient, reliable local network communication between devices.

Question 20

Which wireless standard operates in the 5 GHz band and provides high throughput for modern networks?

A) 802.11a
B) 802.11b
C) 802.11g
D) 802.11n

Answer: A) 802.11a

Explanation

802.11a is one of the early wireless networking standards defined by the IEEE 802.11 family and is specifically designed to operate in the 5 GHz frequency band. Operating in this higher-frequency band provides several advantages compared to the more commonly used 2.4 GHz band. One of the most significant benefits of the 5 GHz band is its relative immunity to interference. The 2.4 GHz band is often crowded due to the presence of numerous household and office devices, including microwave ovens, cordless phones, Bluetooth devices, and other Wi-Fi networks. By operating in the 5 GHz range, 802.11a avoids much of this interference, resulting in more stable and reliable wireless communication, which is particularly important in enterprise environments where consistent connectivity is critical.

In terms of performance, 802.11a supports data transfer speeds of up to 54 Mbps. While this speed is lower than modern standards such as 802.11n or 802.11ac, it was a significant improvement over earlier standards like 802.11b. The higher speed, combined with reduced interference, makes 802.11a suitable for applications requiring fast and reliable wireless connections, such as video conferencing, file transfers, and enterprise network connectivity.

Other wireless standards in the 802.11 family operate differently and are less suitable for exclusive 5 GHz operation. For example, 802.11b operates in the 2.4 GHz frequency band and provides maximum data transfer speeds of up to 11 Mbps. Its operation in the crowded 2.4 GHz band makes it more susceptible to interference, resulting in potential connectivity issues and lower overall network performance. While 802.11b was widely used in the early days of Wi-Fi, its limitations in both speed and frequency make it less suitable for high-performance or interference-sensitive applications.

802.11g is another standard that operates in the 2.4 GHz band but increases data transfer speeds to 54 Mbps, matching the performance of 802.11a. Despite the higher speed, 802.11g still suffers from interference common in the 2.4 GHz range, including signals from Bluetooth devices and microwave ovens. Therefore, while 802.11g provides faster speeds than 802.11b, it does not overcome the interference challenges inherent to the 2.4 GHz spectrum.

802.11n is a more advanced standard capable of operating in both 2.4 GHz and 5 GHz bands, with speeds up to 600 Mbps through the use of multiple-input, multiple-output (MIMO) technology. While 802.11n can utilize the 5 GHz band, it is not exclusively defined for 5 GHz operation. Its dual-band capability offers flexibility, but in scenarios where 5 GHz operation is specifically required, 802.11a is the standard that explicitly defines communication solely in the 5 GHz band.

802.11a is the correct choice when the requirement is for a wireless standard that operates exclusively in the 5 GHz band. It provides reliable, high-speed wireless communication with minimal interference, making it well-suited for enterprise networks and high-performance applications. While other standards such as 802.11b, 802.11g, and 802.11n offer varying speeds and frequency capabilities, only 802.11a is specifically designed for dedicated 5 GHz operation, ensuring optimal performance in interference-prone environments.

Question 21

Which command is used to save the running configuration to startup configuration on a Cisco device?

A) copy running-config startup-config
B) show running-config
C) write erase
D) reload

Answer: A) copy running-config startup-config

Explanation

In Cisco networking devices, configuration management is a crucial aspect of maintaining stable and reliable network operations. When changes are made to a device, such as a router or switch, those changes are initially applied to the running configuration, which is stored in the device’s RAM. The running configuration reflects the current, active settings that the device is using at that moment. While the running configuration allows administrators to test and apply changes immediately, it is volatile, meaning that if the device loses power or is rebooted, all unsaved changes will be lost. Therefore, it is essential to save the running configuration to non-volatile storage to ensure that changes persist across reboots. This is where the copy running-config startup-config command comes into play.

The copy running-config startup-config command takes the current configuration in RAM and copies it into NVRAM, the device’s non-volatile memory. The startup configuration stored in NVRAM is used to initialize the device during boot-up. By executing this command, administrators ensure that any modifications made during the current session are retained even after the device is powered off or restarted. This step is particularly critical after making configuration changes such as interface assignments, routing protocol adjustments, VLAN creation, or security configurations. Without saving the running configuration, all changes would be lost upon reboot, potentially disrupting network operations and causing downtime.

Other Cisco commands are related to configuration management but serve different purposes and do not achieve the goal of saving the running configuration for persistence. For example, the show running-config command is a read-only command that displays the current configuration in memory. While it is useful for verifying settings, auditing changes, or troubleshooting, it does not save any configuration to NVRAM. It simply provides a snapshot of the active configuration at a given time.

The write erase command, on the other hand, deletes the startup configuration stored in NVRAM. Executing this command effectively resets the device to a default state, removing all saved configurations. While this may be useful for resetting a device or preparing it for a new configuration, it does not save any changes made to the running configuration.

The reload command reboots the device but does not automatically save the running configuration unless explicitly combined with a command to do so. If administrators restart a device without saving the running configuration first, all unsaved changes will be lost. This is a common pitfall for network engineers and highlights the importance of executing copy running-config startup-config after making modifications.

The copy running-config startup-config command is the correct and necessary choice for ensuring configuration persistence on Cisco devices. It transfers all active changes from the running configuration in RAM to the startup configuration in NVRAM, safeguarding the network against loss of critical settings during reboots or power interruptions. By routinely using this command, administrators maintain network stability, reliability, and consistency, making it an indispensable part of standard Cisco device management procedures.

Question 22

Which protocol provides automatic IP address assignment for hosts?

A) DHCP
B) DNS
C) ARP
D) ICMP

Answer: A) DHCP

Explanation

Dynamic Host Configuration Protocol, commonly known as DHCP, is a fundamental network protocol used to automate the process of assigning IP addresses and other essential network configuration information to devices on a network. In modern networks, every device requires a unique IP address to communicate effectively with other devices, routers, servers, and internet services. Manually assigning IP addresses to every device in a network can be time-consuming, error-prone, and prone to conflicts, particularly in large-scale enterprise networks. DHCP eliminates these challenges by providing a centralized mechanism to automatically assign IP addresses, along with other critical network parameters such as subnet masks, default gateways, and DNS server addresses.

When a device, such as a computer, smartphone, or IoT device, connects to a network, it sends out a DHCP discovery message to locate available DHCP servers. The DHCP server responds with an offer that includes an available IP address and other configuration settings. The device then requests this information, and the server confirms the allocation. This process, often referred to as the DHCP lease process, ensures that each device receives a valid IP address for a specified period, after which it can be renewed. By automating this process, DHCP significantly reduces administrative overhead, prevents IP address conflicts, and simplifies network management.

It is important to understand how DHCP differs from other network protocols that deal with addressing or network communication. For example, the Domain Name System, or DNS, is responsible for resolving human-readable hostnames into IP addresses. While DNS is essential for locating devices or services using domain names, it does not assign IP addresses to devices or provide network configuration information. Its primary purpose is name resolution, not address allocation.

The Address Resolution Protocol, or ARP, maps IP addresses to MAC addresses on a local network. ARP allows devices to determine the physical hardware address of a device with a known IP address, facilitating communication at the data link layer. However, ARP does not handle the automatic assignment of IP addresses, subnet masks, gateways, or DNS information. It only resolves known IP addresses to MAC addresses for local communication.

The Internet Control Message Protocol, or ICMP, is used for network diagnostics and error reporting. Commonly associated with the ping command, ICMP allows devices to test connectivity and report issues such as unreachable hosts or network congestion. While ICMP is vital for troubleshooting and network performance monitoring, it does not provide any mechanism for assigning IP addresses or other configuration parameters.

Given the need to automatically assign IP addresses, subnet masks, gateways, and DNS information to hosts, DHCP is the correct protocol. By automating these assignments, DHCP streamlines network management, reduces the likelihood of errors, and ensures that devices can join and communicate on a network efficiently. It is indispensable in modern networks, supporting scalability, consistency, and operational reliability, making it the ideal solution for automatic IP address allocation.

Question 23

Which command is used to test connectivity between two devices and measure response time?

A) ping
B) traceroute
C) show ip route
D) show interfaces

Answer: A) ping

Explanation

The ping command is one of the most fundamental and widely used tools in networking, designed to test the connectivity between a source device and a target host on a network. It operates by sending Internet Control Message Protocol (ICMP) echo request messages to the target device and then waiting for ICMP echo reply messages in response. This process allows network administrators and engineers to verify whether a host is reachable, measure the time it takes for data to travel to the destination and back, and detect potential network issues. The simplicity and effectiveness of ping make it a crucial first step in troubleshooting network problems and ensuring reliable communication between devices.

When a ping is executed, the tool provides several pieces of important information. It indicates whether the target device responded successfully, which confirms basic network connectivity. In addition, it provides round-trip time statistics, which measure the latency between the source and destination. High latency or packet loss detected during a ping test can reveal network congestion, faulty links, misconfigured devices, or other issues affecting performance. By providing immediate feedback, ping allows administrators to quickly assess the state of the network and determine whether further investigation or corrective action is required.

Other networking commands serve different purposes and are not designed for the same type of basic connectivity testing that ping provides. Traceroute, for example, maps the path that packets take from the source to the destination by listing all intermediate hops along the route. While traceroute is valuable for identifying where delays or failures occur along a network path, it is not primarily used for verifying basic reachability or measuring the simple round-trip time to a single host. Its focus is on path analysis rather than straightforward connectivity testing.

Similarly, the show ip route command, commonly used on routers, displays the contents of the router’s routing table. It provides information about directly connected networks, learned routes, and the administrative distance of each path. While this command is useful for understanding how a router will forward packets, it does not actively test connectivity to a specific remote device. It is a static view of routing information rather than a dynamic tool for verifying network communication.

The show interfaces command provides detailed information about the operational status and statistics of a device’s interfaces, including interface errors, traffic counters, and link status. While this information is valuable for monitoring and troubleshooting local interfaces, it does not test connectivity to remote hosts or provide round-trip time measurements.

Given that the primary task is to verify connectivity to a target device and measure response time, ping is the most appropriate and effective command. It combines simplicity with actionable insights, confirming whether a host is reachable, providing latency information, and allowing administrators to quickly identify potential network issues. Its direct approach to connectivity testing makes it an indispensable tool in network troubleshooting and monitoring, enabling efficient identification and resolution of problems across local and wide-area networks.

Question 24

Which layer of the OSI model is responsible for physical addressing and MAC addresses?

A) Data Link
B) Network
C) Transport
D) Application

Answer: A) Data Link

Explanation

The Data Link layer is a critical component of the OSI (Open Systems Interconnection) model, responsible for enabling reliable communication between devices within the same local network segment. Operating at Layer 2 of the OSI model, the Data Link layer provides the foundation for node-to-node communication by using Media Access Control (MAC) addresses to uniquely identify devices on the network. By organizing data into frames and managing their delivery between devices on the same physical network, the Data Link layer ensures that information is transmitted efficiently, accurately, and without collisions. This layer plays a vital role in maintaining the integrity of data as it travels across a single network segment, bridging the gap between the physical transmission of signals and higher-level networking functions.

One of the primary responsibilities of the Data Link layer is addressing and delivering frames using MAC addresses. Each device on a local area network (LAN) has a unique MAC address assigned to its network interface card (NIC). When a device wants to send data to another device on the same network, the Data Link layer encapsulates the data from the Network layer into a frame and includes the destination device’s MAC address. Network switches use these MAC addresses to forward frames to the correct destination port, ensuring that data reaches the intended recipient without unnecessary broadcasting across the entire network.

In addition to addressing, the Data Link layer handles error detection and, in some cases, error correction. Techniques such as cyclic redundancy checks (CRC) are employed to verify the integrity of frames as they traverse the network. If an error is detected, the frame can be discarded or retransmitted, depending on the network protocol. Flow control mechanisms are also implemented at this layer to prevent network congestion and ensure that devices do not overwhelm one another with excessive data. These functions collectively enhance the reliability and efficiency of local network communications.

Other layers of the OSI model provide complementary but distinct functions. The Network layer, or Layer 3, is responsible for logical addressing using IP addresses and routing packets across multiple networks. While it directs data between different subnets or geographic locations, it does not manage MAC addresses or the delivery of frames within a single LAN. The Transport layer, or Layer 4, focuses on end-to-end delivery, error recovery, segmentation, and reassembly of data, ensuring that complete messages reach the correct application processes on remote hosts. It operates independently of MAC addressing and local network segment concerns.

The Application layer, at the top of the OSI model, provides services directly to end-user applications, such as email, web browsing, and file transfer. It does not handle addressing, frame delivery, or local network reliability.

Given that the specific requirement is to identify the layer responsible for MAC addressing, node-to-node delivery, and reliable frame transmission within a local network segment, the Data Link layer is the correct answer. By managing hardware addressing, error detection, and flow control, it ensures that devices on the same network segment can communicate effectively, forming a critical bridge between the physical transmission of data and higher-level network functions.

Question 25

Which protocol provides hostname to IP address resolution?

A) DNS
B) DHCP
C) ARP
D) ICMP

Answer: A) DNS

Explanation

The Domain Name System, or DNS, is a critical component of modern networking that allows users and applications to access devices and services using human-readable names instead of numeric IP addresses. Every device connected to a network, whether on a local network or the internet, is assigned an IP address, which serves as a unique identifier for routing data packets. However, memorizing and using numeric IP addresses for every website, server, or network resource would be highly impractical. DNS solves this problem by providing a hierarchical and distributed system that translates user-friendly domain names, into the corresponding IP addresses required for communication between devices. This translation process, known as name resolution, enables seamless network navigation and access to resources.

When a user enters a hostname into a web browser or any application that requires network connectivity, the device first queries a DNS resolver, which then communicates with DNS servers to determine the correct IP address associated with the hostname. The resolver may consult cached results to speed up the process or query authoritative DNS servers if necessary. Once the IP address is obtained, the device can initiate communication with the target server or resource, routing packets to the correct destination using standard networking protocols. This entire process occurs automatically and transparently, allowing users to interact with network resources without needing to understand or remember complex IP addressing schemes.

It is important to differentiate DNS from other networking protocols that are sometimes confused with it. Dynamic Host Configuration Protocol, or DHCP, is responsible for dynamically assigning IP addresses and other network configuration information, such as subnet masks, default gateways, and DNS server addresses, to devices on a network. While DHCP ensures that devices receive valid IP addresses, it does not perform hostname-to-IP resolution and is therefore not a substitute for DNS.

The Address Resolution Protocol, or ARP, operates within a local network segment and maps IP addresses to MAC addresses. ARP enables devices to communicate at the data link layer by resolving the hardware address of a known IP address, allowing Ethernet frames to be delivered correctly. While ARP is essential for local network communication, it does not provide the capability to translate hostnames into IP addresses.

Similarly, the Internet Control Message Protocol, or ICMP, is used for diagnostics and error reporting. ICMP enables tools such as ping and traceroute to test connectivity, measure latency, and report unreachable hosts. However, ICMP does not perform any form of name resolution or mapping between hostnames and IP addresses.

Given the requirement to translate human-readable hostnames into numeric IP addresses to enable easier access to network resources, DNS is the correct protocol. It plays a foundational role in both local and global networking, providing an efficient and scalable system for resolving names, facilitating seamless communication, and supporting the usability of networked applications and services. Without DNS, users would need to rely on numeric addresses for every resource, making network navigation cumbersome and prone to errors.

Question 26

Which technology prevents broadcast storms in a Layer 2 network?

A) Spanning Tree Protocol (STP)
B) VLANs
C) EtherChannel
D) DHCP Snooping

Answer: A) Spanning Tree Protocol (STP)

Explanation

Spanning Tree Protocol, commonly known as STP, is a fundamental technology in Ethernet networking that ensures reliable and loop-free operation within Layer 2 networks. In a typical LAN environment, switches are often connected using multiple physical paths to provide redundancy. While redundancy enhances network reliability by offering alternative paths if a link fails, it can also create a significant problem: network loops. Loops occur when frames circulate endlessly between switches, consuming bandwidth and potentially leading to broadcast storms, where broadcast and multicast traffic overwhelm the network. STP was developed to address these challenges by identifying redundant paths and selectively blocking them, ensuring that only one active path exists between any two switches at a time.

STP operates by electing a root bridge and determining the shortest path from each switch to the root. All other redundant paths are placed in a blocking state, preventing frames from looping indefinitely. The protocol continuously monitors the network, and if the active path fails, STP recalculates the topology and activates an alternative path to maintain connectivity. This dynamic approach ensures that the network remains resilient to failures while avoiding the destructive effects of loops and broadcast storms. By maintaining a loop-free topology, STP not only preserves bandwidth but also enhances overall network stability, which is crucial in enterprise environments with multiple interconnected switches.

It is important to distinguish STP from other network technologies that are sometimes confused with it but do not serve the same function. Virtual Local Area Networks, or VLANs, segment a network logically into separate broadcast domains. While VLANs reduce unnecessary broadcast traffic within each segment and improve network organization, they do not inherently prevent loops between switches. If redundant connections exist between VLAN-aware switches, a loop can still form unless STP or a similar protocol is implemented.

EtherChannel is another technology often associated with redundancy. It allows multiple physical links between switches to be combined into a single logical link, increasing bandwidth and providing fault tolerance. While EtherChannel ensures that traffic is load-balanced across multiple physical connections, it does not inherently prevent Layer 2 loops. Without STP, loops can still occur even when EtherChannel is deployed.

DHCP Snooping is a security feature designed to prevent unauthorized or rogue DHCP servers from assigning IP addresses on a network. While it enhances network security by controlling IP address allocation, DHCP Snooping does not address the issue of loops or broadcast storms in Layer 2 topologies.

Given the need to prevent continuous circulation of frames and the resulting broadcast storms in a Layer 2 network, Spanning Tree Protocol is the correct technology. By intelligently identifying redundant paths and blocking them while maintaining network resilience, STP ensures stable, efficient, and loop-free operation, making it an indispensable protocol in modern Ethernet network design.

Question 27

Which IPv4 address is reserved for loopback testing?

A) 127.0.0.1
B) 192.168.1.1
C) 10.0.0.1
D) 172.16.0.1

Answer: A) 127.0.0.1

Explanation

The IPv4 address 127.0.0.1 is reserved for loopback testing on a host. It allows testing the TCP/IP stack locally without sending traffic over a physical network interface.

192.168.1.1 is a private IP commonly used as a gateway address in LANs, not for loopback.

10.0.0.1 is part of the Class A private address range and is not reserved for loopback purposes.

172.16.0.1 belongs to the Class B private address range and is not used for loopback testing.

Because 127.0.0.1 is specifically reserved for local loopback tests, it is the correct answer.

Question 28

Which command is used to view detailed interface statistics on a Cisco device?

A) show interfaces
B) show ip route
C) ping
D) traceroute

Answer: A) show interfaces

Explanation

The show interfaces command displays detailed interface information, including operational status, IP address, bandwidth, errors, and packet statistics. It is essential for troubleshooting interface-level issues.

Show ip route displays routing table entries but does not provide detailed interface statistics.

Ping tests connectivity but does not provide interface-level statistics.

Traceroute shows the path packets take across multiple hops but does not display interface metrics.

Because the task is to view detailed interface statistics, show interfaces is the correct command.

Question 29

Which layer of the OSI model provides end-to-end error detection and reliable delivery?

A) Transport
B) Network
C) Data Link
D) Physical

Answer: A) Transport

Explanation

The Transport layer provides segmentation, flow control, error detection, and reliable delivery between end devices. Protocols like TCP ensure that data arrives intact and in order.

The Network layer handles logical addressing and routing but does not guarantee reliability.

The Data Link layer detects errors on a local network segment but cannot ensure end-to-end delivery.

The Physical layer transmits raw bits and provides no error detection or reliable delivery.

Since the requirement is end-to-end reliability, the Transport layer is correct.

Question 30

Which type of IPv6 address is assigned to multiple devices, with traffic delivered to the nearest device in the group?

A) Anycast
B) Unicast
C) Multicast
D) Link-Local

Answer: A) Anycast

Explanation

Anycast addresses are assigned to multiple devices, and packets sent to an anycast address are delivered to the nearest device based on routing metrics. This provides efficient service delivery and load distribution.

Unicast addresses identify a single interface for one-to-one communication.

Multicast addresses send packets to all devices subscribed to a group, not necessarily the nearest device.

Link-Local addresses are used for communication within a single link and are not designed for delivery to multiple nodes based on proximity.

Because the question specifies traffic delivery to the nearest device, Anycast is correct.