Cisco 200-301 Cisco Certified Network Associate (CCNA) Exam Dumps and Practice Test Questions Set 12 Q165-180
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Question 166
Which command displays the routes a device has learned through EIGRP?
A) show ip route eigrp
B) show ip route ospf
C) show ip protocols
D) show running-config
Answer: A) show ip route eigrp
Explanation
In networking, understanding the routes that a device has learned through specific routing protocols is essential for effective troubleshooting, network optimization, and ensuring proper packet delivery. Enhanced Interior Gateway Routing Protocol, or EIGRP, is a dynamic routing protocol used in many enterprise networks to facilitate the exchange of routing information between routers. To analyze the routes that a device has learned through EIGRP, the command show ip route eigrp is particularly valuable. This command displays a detailed list of all routes that were learned via EIGRP, including the destination networks, next-hop IP addresses, and administrative distances. By examining this information, network administrators can gain a clear understanding of how EIGRP is influencing routing decisions on the device and verify that the network is functioning as intended.
The information provided by show ip route eigrp is critical in multiple scenarios. For instance, when troubleshooting connectivity issues, an administrator can use this command to confirm whether a route to a specific network is being learned through EIGRP and to identify the next-hop IP that will be used to forward traffic. This helps pinpoint where potential routing problems might exist, such as incorrect EIGRP configuration, missing network statements, or interface issues that prevent proper route propagation. Additionally, examining the administrative distance associated with each EIGRP route allows administrators to understand the trustworthiness of the routing information compared to other routing protocols that may be active on the device. Since EIGRP uses a default administrative distance of 90, routes learned through EIGRP will generally take precedence over routes learned through protocols with higher distances, such as OSPF.
Other commands might seem relevant but do not provide the same level of specificity for EIGRP-learned routes. For example, show ip route ospf displays only routes that were learned via the OSPF routing protocol. While this is useful when troubleshooting OSPF, it does not provide any visibility into the routes learned through EIGRP, which is the focus of the question. Similarly, show ip protocols gives an overview of which routing protocols are configured on a device, including timers, networks, and redistribution settings, but it does not display the actual routes that have been learned or their next-hop information. This limits its utility when the goal is to see the specific routing entries that EIGRP has contributed to the routing table. Finally, show running-config displays the device’s active configuration, including EIGRP process settings, network statements, and interface configurations, but it does not provide real-time information about the dynamically learned routes.
Because the question specifically asks about routes learned via EIGRP, show ip route eigrp is the correct and most appropriate command. It provides detailed, route-specific information that is essential for verifying EIGRP functionality, troubleshooting routing issues, and ensuring that network traffic is being forwarded according to the intended design. By using this command, network administrators can gain complete visibility into the EIGRP routing table, identify any anomalies or missing routes, and make informed decisions about network management and optimization. It is a fundamental tool for managing and monitoring EIGRP-enabled networks.
Question 167
Which command clears the ARP table on a Cisco device?
A) clear arp-cache
B) show arp
C) show mac address-table
D) show ip interface brief
Answer: A) clear arp-cache
Explanation
In networking, the Address Resolution Protocol (ARP) plays a critical role in enabling communication within a local network by mapping IP addresses to MAC addresses. Devices maintain an ARP table, which contains the IP-to-MAC address mappings for hosts they have communicated with. Over time, entries in the ARP table can become outdated, incorrect, or even duplicated, which can cause communication issues or network inefficiencies. To address these problems, network administrators use the command clear arp-cache, which removes all existing ARP entries from a device’s ARP table. By clearing the ARP cache, the device is forced to rebuild its table by sending out ARP requests to learn the correct MAC addresses for the IP addresses it needs to communicate with. This action ensures that the ARP table contains only fresh and accurate mappings, which is particularly useful for troubleshooting stale entries, duplicate IP conflicts, or connectivity issues within a subnet.
When a network device has an incorrect or outdated ARP entry, it may attempt to send traffic to the wrong MAC address, resulting in failed communication. For example, if two devices in a network share the same IP due to misconfiguration, the ARP table may contain a mapping pointing to the wrong device. Clearing the ARP cache resolves such conflicts by forcing the device to relearn the correct MAC addresses from the network, eliminating errors caused by old or conflicting entries. This process is especially helpful in dynamic network environments where devices frequently join and leave the network, such as in offices with mobile devices, virtualized servers, or DHCP-assigned IP addresses.
Other commands in network administration may provide ARP-related information but do not perform the same function as clear arp-cache. For instance, the show arp command displays the current contents of the ARP table, allowing administrators to view the IP-to-MAC mappings that are currently stored on a device. While this is useful for monitoring or diagnosing network issues, it does not remove or refresh the entries. Similarly, show mac address-table displays MAC addresses that a switch has learned on its ports, which is valuable for mapping devices to switch interfaces but does not interact with ARP tables. Another related command, show ip interface brief, provides information about the IP addresses and operational status of interfaces, but it does not affect ARP entries or their accuracy.
Because the question specifically asks about removing or clearing ARP entries from a device, the clear arp-cache command is the correct choice. It directly addresses the need to refresh the ARP table and ensures that the device will acquire updated MAC address information through new ARP requests. By using this command, network administrators can quickly resolve issues caused by stale or incorrect ARP entries, improve connectivity, and maintain accurate network mappings. The ability to clear the ARP cache is an essential tool in troubleshooting and maintaining healthy network operation, providing a straightforward method to ensure that IP-to-MAC address relationships are current and reliable, and helping prevent communication problems within the local network.
Question 168
Which protocol maps IP addresses to MAC addresses on a local network?
A) ARP
B) DNS
C) DHCP
D) ICMP
Answer: A) ARP
Explanation
Address Resolution Protocol, commonly known as ARP, is a fundamental protocol in computer networking that enables devices on a local network to map IPv4 addresses to their corresponding MAC addresses. This mapping is essential because while higher-level protocols, such as IP, operate with logical addresses to identify devices, the actual delivery of packets on a local area network relies on MAC addresses, which are hardware-level identifiers unique to each network interface. ARP serves as the bridge between these two addressing schemes, ensuring that data can move from one device to another efficiently and accurately within a single broadcast domain.
When a device needs to communicate with another device on the same subnet, it must know the MAC address associated with the destination IP address. If the MAC address is not already stored in the device’s ARP cache, the device will broadcast an ARP request to all hosts on the local network segment, essentially asking, “Who owns this IP address?” The device with the corresponding IP address responds with its MAC address, which is then stored in the ARP cache for future communication. This process allows devices to transmit Ethernet frames correctly to their intended recipients, facilitating seamless communication within the local network.
Other protocols, while important in networking, do not serve this specific function. Domain Name System, or DNS, translates human-readable hostnames, like www.example.com, into IP addresses. DNS is crucial for enabling users and applications to find resources across networks, but it does not resolve IP addresses to MAC addresses, which is the task ARP performs. Dynamic Host Configuration Protocol, or DHCP, is responsible for dynamically assigning IP addresses to devices on a network. While DHCP helps manage IP addressing efficiently, it does not provide the mechanism for mapping these IP addresses to hardware MAC addresses. Similarly, Internet Control Message Protocol, or ICMP, is primarily used for network diagnostics and error messaging, such as testing connectivity with ping or reporting unreachable hosts. ICMP provides valuable feedback about network conditions but does not resolve address mappings between IP and MAC.
The significance of ARP extends beyond simple address resolution. Efficient network communication relies on ARP’s ability to quickly provide the correct MAC address for packet delivery. Without ARP, devices would be unable to send frames to the correct destination within a local network, leading to failed communication and network disruption. ARP also interacts closely with network devices like switches and routers to ensure proper forwarding of traffic and maintain the integrity of local network communication.
Because the question specifically emphasizes the need to resolve an IP address into its corresponding MAC address, ARP is unequivocally the correct protocol. It directly addresses the problem of translating logical IP addresses to physical hardware identifiers, enabling devices to communicate effectively within the same local network segment. None of the other protocols—DNS, DHCP, or ICMP—fulfill this role, making ARP uniquely suited for the task and an essential component of everyday networking operations.
Question 169
Which command displays the running configuration of a Cisco device?
A) show running-config
B) show startup-config
C) copy running-config startup-config
D) show version
Answer: A) show running-config
Explanation
In networking, it is often critical for administrators to verify the current configuration of a device to ensure it is operating as intended and to troubleshoot any potential issues. On Cisco devices, the command show running-config provides a comprehensive view of the active configuration that is currently stored in the device’s RAM. This configuration reflects all changes made since the last reload or restart of the device, including interface settings, routing protocols, access control lists, VLAN configurations, and other critical parameters. By using show running-config, network administrators can quickly confirm the current operational state of the device and validate that all intended configurations are applied correctly.
The running configuration displayed by this command is dynamic, meaning it includes any changes that have been made but not yet saved to non-volatile memory. This allows administrators to immediately see the effects of recent changes, whether they were implemented manually through the command-line interface or applied automatically by configuration scripts. The visibility into the current configuration is essential for troubleshooting, auditing, and planning future modifications. For example, if an interface is not operating correctly or a routing protocol is not functioning as expected, show running-config can reveal misconfigurations or missing commands that are causing the issue. It provides a clear and detailed representation of how the device is currently set up and how it interacts with the rest of the network.
Other commands, while related to configuration management, do not serve the same purpose. Show startup-config displays the configuration stored in NVRAM, which is the version that will be loaded when the device next restarts. This configuration may differ from the running configuration if recent changes have not been saved. While useful for confirming what will persist after a reboot, show startup-config does not reflect the current operational state of the device. Copy running-config startup-config is a command used to save the active configuration from RAM to NVRAM, ensuring that all modifications are preserved across device reloads. Show version, on the other hand, provides system-level information such as the device model, software version, memory, and uptime, but it does not display any configuration details, making it irrelevant for verifying current settings.
The importance of show running-config is further highlighted in network management tasks such as troubleshooting connectivity issues, verifying security policies, and auditing configuration changes. By giving a complete view of the active settings, it enables administrators to detect inconsistencies, confirm that intended changes have been applied, and ensure that interfaces, VLANs, routing protocols, and other features are correctly configured. Because the question specifically asks for the current, active configuration of the device, show running-config is the most appropriate and accurate command. It provides real-time insight into the device’s configuration, which is indispensable for effective network management and operational reliability.
Question 170
Which type of IPv4 address sends data to all hosts in a subnet?
A) Broadcast
B) Unicast
C) Multicast
D) Anycast
Answer: A) Broadcast
Explanation
In computer networking, addressing plays a crucial role in determining how data is delivered across a network. One specific type of address, the broadcast address, is used to send data to all devices within a particular subnet. This means that any packet sent to a broadcast address is received by every host on that subnet, allowing for one-to-all communication. Broadcast communication is essential in many network operations because it enables devices to efficiently distribute information without having to send individual messages to each host, which would be less efficient and more resource-intensive.
A common use case for broadcast addresses is the Address Resolution Protocol, or ARP. When a device needs to determine the MAC address corresponding to a particular IP address on the local network, it sends an ARP request to the broadcast address. All devices on the subnet receive this request, but only the device with the matching IP address responds. This process ensures that data can be correctly delivered at the data link layer and highlights the importance of broadcast addresses for enabling basic network communication. Beyond ARP, broadcast addresses are also used for sending network-wide announcements, such as informing all devices about certain services or network changes, further emphasizing their role in efficient communication within a local network.
In contrast, other types of addressing serve different purposes. Unicast addresses are used for one-to-one communication, meaning that a packet is sent from one device directly to another specific device. While unicast is the most common form of communication on networks, it does not facilitate communication with multiple devices simultaneously, unlike broadcast. Multicast addresses, on the other hand, are designed for one-to-many communication but only target a specific group of devices that have subscribed to receive those packets. Multicast is particularly useful for applications like video streaming or conferencing, where only certain devices need the data. Anycast addresses are another unique form of addressing, where packets are delivered to the nearest device among a group of devices sharing the same address. Anycast is commonly used in distributed services like DNS or content delivery networks to reduce latency and optimize network efficiency.
Because the question focuses specifically on sending data to all hosts within a subnet, broadcast addressing is the correct choice. It is uniquely capable of reaching every device on the subnet simultaneously, something that unicast, multicast, or anycast cannot achieve in the same way. Understanding broadcast addresses is fundamental for network administrators, as it allows them to design and troubleshoot networks effectively, ensuring that important messages, service requests, and network management communications reach all intended devices. The ability of broadcast addresses to facilitate one-to-all communication makes them an indispensable part of local network operations and a key tool in the proper functioning of subnet-level communications.
Question 171
Which command displays all VLANs configured on a switch?
A) show vlan brief
B) show running-config
C) show interfaces
D) show mac address-table
Answer: A) show vlan brief
Explanation
In network management, particularly when dealing with switches, it is important to have a clear and efficient way to verify the configuration and status of VLANs, or Virtual Local Area Networks. VLANs allow a single physical network to be segmented into multiple logical networks, enhancing security, improving traffic management, and enabling better use of network resources. To effectively manage VLANs, network administrators need tools that provide accurate and concise information about their configuration, including VLAN identifiers, names, and operational status. One of the most useful commands for this purpose on a Cisco switch is show vlan brief. This command provides a summarized overview of all VLANs that are currently configured on the device. When executed, it displays a list of VLAN IDs, their corresponding names, and their operational status, allowing administrators to quickly assess the overall VLAN setup on the switch. This concise output makes it easy to verify that VLANs are correctly configured and active without having to sift through extensive configuration details. It is particularly useful when troubleshooting connectivity issues or when performing audits to ensure VLAN assignments align with the intended network design.
While show vlan brief is ideal for obtaining a high-level overview of VLANs, other commands provide different types of information that are less suited for quick VLAN verification. For example, show running-config displays the full active configuration stored in the device’s memory. Although this command does include VLAN configurations, it outputs all aspects of the switch configuration, including interface settings, routing protocols, access control lists, and more. As a result, using show running-config to verify VLANs can be cumbersome, since the VLAN information is embedded within a large amount of other data. Administrators may have to scroll through many lines of configuration to locate the VLAN details, which is time-consuming and less efficient compared to the straightforward provided by show vlan brief.
Similarly, the show interfaces command provides detailed statistics and operational status for individual interfaces, including speed, duplex, errors, and traffic statistics. However, it does not offer a of VLANs across the switch, and therefore is not the most efficient tool for quickly verifying which VLANs are configured or active.
The show mac address-table command, while important for mapping MAC addresses to switch ports, also does not provide VLAN summaries. It is mainly used for understanding how traffic is flowing through the switch and which devices are connected to which ports.
Because the specific task is to verify all VLANs configured on a switch, show vlan brief is the most appropriate and efficient choice. It delivers a clear, concise of VLAN IDs, names, and operational status in a single view, enabling administrators to quickly confirm the VLAN configuration, ensure proper segmentation, and identify any inactive or misconfigured VLANs without having to parse through more detailed configuration or statistics commands. This makes show vlan brief an essential tool in day-to-day VLAN management and troubleshooting.
Question 172
Which type of IPv6 address allows communication with all nodes on a local network segment?
A) Link-local
B) Global unicast
C) Multicast
D) Anycast
Answer: A) Link-local
Explanation
In IPv6 networking, understanding address types and their purposes is critical for designing and maintaining efficient and functional networks. One important type of address that is automatically assigned to every IPv6-enabled interface is the link-local address. Link-local addresses fall within the FE80::/10 address block and are designed to enable communication between devices on the same physical or logical link. These addresses are fundamental to the operation of IPv6, as they are required for essential network functions, including neighbor discovery, address autoconfiguration, and routing protocol operations such as OSPFv3 and EIGRP for IPv6. Because they are automatically assigned, administrators do not need to manually configure link-local addresses for basic local communication, making them a critical component of IPv6 networks. They are always present on every IPv6-enabled interface and are used even when no global or unique local addresses are configured.
Unlike link-local addresses, global unicast addresses are routable on the public internet. These addresses are unique and are assigned either manually by an administrator or automatically via mechanisms such as DHCPv6 or SLAAC. Global unicast addresses enable devices to communicate across networks and are necessary for internet connectivity. While global unicast addresses are essential for long-range communication, they are not used for local link communications, which is the specific role of link-local addresses.
Multicast addresses in IPv6 serve a different function. They are used for one-to-many communication, allowing a single packet to be delivered to multiple subscribed devices. Multicast addresses are important for efficient group communication, such as sending routing updates or streaming services, but they are not automatically assigned for basic device-to-device link communication and therefore are not suitable for tasks that require automatic local link connectivity.
Anycast addresses are another type of IPv6 address. They are assigned to multiple interfaces, typically on different devices, and packets sent to an anycast address are delivered to the nearest interface based on routing metrics. Anycast is widely used for distributed services like DNS or content delivery networks, where the goal is to reach the closest server. However, anycast addresses are not automatically configured for local link use and are not intended for basic link-local communication.
Because the question specifies automatic assignment for communication within the same local link, link-local addresses are the correct choice. They are inherently present on all IPv6 interfaces, ensure immediate local connectivity, and support critical protocols like neighbor discovery, making them indispensable for the initial operation of IPv6 networks. Their automatic nature allows devices to communicate with one another on the same link without requiring manual configuration, which simplifies deployment and ensures fundamental network functions operate correctly. Link-local addresses provide the essential functionality for local link communication, differentiating them clearly from global unicast, multicast, and anycast addresses.
Question 173
Which command displays all IP addresses leased by a DHCP server?
A) show ip dhcp binding
B) show ip interface brief
C) show running-config
D) show arp
Answer: A) show ip dhcp binding
Explanation
In network administration, especially in environments using dynamic addressing, it is crucial to track which IP addresses have been assigned to clients and to which devices or interfaces these addresses correspond. In Cisco networking, the command show ip dhcp binding serves this exact purpose. When executed, this command displays a list of all IP addresses currently leased by the DHCP server to clients within the network. Alongside each IP address, the command output provides essential information such as the MAC address of the client device, the duration of the lease, and the interface through which the lease was granted. This information is invaluable for administrators because it allows them to verify which devices have been assigned which addresses, monitor the utilization of the DHCP pool, troubleshoot IP conflicts, and ensure proper network allocation.
The ability to view leased IP addresses directly via show ip dhcp binding makes it a central tool in DHCP management. Without such a command, administrators would need to manually cross-reference the running configuration or other records, which is time-consuming and prone to error. It provides a clear and immediate view of the dynamic IP environment, making it straightforward to determine which clients are active, which addresses are still available, and whether any devices have incorrect or outdated leases. The command is particularly useful in larger networks where hundreds or thousands of devices may rely on DHCP for addressing, as manually tracking this information would be nearly impossible.
Other commands often used for network verification provide complementary but different types of information. For instance, show ip interface brief displays the status and IP addresses of interfaces on the device, including whether the interface is administratively up or down and its protocol state. While this is useful for confirming connectivity and IP assignments on the local interfaces, it does not provide any information about which IP addresses have been leased to clients through DHCP or their lease durations. Similarly, show running-config displays the active configuration of the device stored in RAM, including any DHCP pool configurations, interface settings, and routing information, but it does not list current active leases. Show arp displays IP-to-MAC mappings, which can be useful for identifying which MAC addresses correspond to which IPs on the local network, but it does not show which addresses were dynamically assigned by DHCP or the lease status.
Because the question specifically asks about the IP addresses that have been leased to clients, show ip dhcp binding is the correct command to use. It directly addresses the need to see active DHCP leases, along with relevant details such as the client MAC addresses, lease durations, and associated interfaces. This makes it the most appropriate and efficient tool for verifying dynamic IP assignments, tracking address utilization, and troubleshooting any issues related to DHCP in the network. By providing a real-time snapshot of the DHCP bindings, the command ensures administrators have precise control and visibility over their network’s dynamic addressing environment.
Question 174
Which type of VLAN is used for administrative tasks such as device management?
A) Management VLAN
B) Voice VLAN
C) Data VLAN
D) Native VLAN
Answer: A) Management VLAN
Explanation
In networking, VLANs, or Virtual Local Area Networks, are used to logically segment a network into separate broadcast domains. One of the most important types of VLANs is the Management VLAN. The Management VLAN is specifically designed to handle administrative traffic for network devices, which includes protocols and services such as Secure Shell (SSH), Telnet, and Simple Network Management Protocol (SNMP). This VLAN is distinct from regular data or voice traffic, which is critical for both performance and security. By isolating administrative traffic from user and voice communications, the Management VLAN reduces the risk of unauthorized access to network devices and ensures that administrative functions can operate reliably without interference from heavy user traffic.
The primary purpose of the Management VLAN is to provide a secure channel for network administrators to access and configure devices such as switches, routers, and firewalls. When a device is configured to use a Management VLAN, all administrative operations, including configuration changes, monitoring, and troubleshooting, are carried over a dedicated path. This separation is crucial because it minimizes the likelihood that sensitive administrative traffic could be intercepted or disrupted by ordinary network traffic. For example, if management traffic were to share the same VLAN as user data, there would be a higher risk of exposure to potential attacks or accidental disruptions, which could compromise the entire network infrastructure.
Other VLAN types serve different purposes within a network. Voice VLANs, for instance, are used exclusively for IP phone traffic. By placing voice traffic in a separate VLAN, administrators can prioritize it using Quality of Service (QoS) mechanisms to ensure clear and uninterrupted communication. Data VLANs carry standard user traffic such as file transfers, web browsing, and application usage. These VLANs handle the bulk of day-to-day network activity but are not suitable for administrative tasks, as combining them with management traffic could lead to congestion and security risks. Native VLANs are used on trunk ports to handle untagged traffic. While they facilitate communication between devices that do not support VLAN tagging, they are not intended for carrying administrative traffic.
The distinction between these VLAN types highlights why the Management VLAN is essential for network administration. By isolating sensitive administrative traffic, it provides an extra layer of security, helps prevent accidental misconfigurations, and allows administrators to monitor and manage devices more effectively. This separation also simplifies troubleshooting and auditing, as administrators can easily identify and control the flow of management traffic without interference from other types of network communication.
Because the question specifically asks about administrative traffic and functions, the Management VLAN is the appropriate choice. It is designed to ensure that tasks like SSH access, Telnet sessions, and SNMP monitoring are conducted securely and efficiently, making it a foundational element in network design and management. By dedicating a VLAN exclusively for management purposes, networks achieve a higher level of security, operational efficiency, and overall stability, ensuring that critical administrative operations remain uninterrupted and protected.
Question 175
Which type of IPv6 address delivers packets to the nearest device among multiple devices sharing the same address?
A) Anycast
B) Unicast
C) Multicast
D) Link-local
Answer: A) Anycast
Explanation
Anycast addressing is a specialized network addressing technique used primarily in IPv6, although it can also be implemented in IPv4 in limited scenarios. The core idea of Anycast is to assign the same IP address to multiple devices that provide a particular service or function within a network. Unlike unicast, which targets a single device, or multicast, which delivers data to a predefined group, Anycast allows multiple devices to share one address while ensuring that network traffic is delivered to the nearest device based on routing metrics. The “nearest” device is determined by the network’s routing protocol, which calculates the shortest path in terms of distance, hop count, or other defined metrics. This approach enhances efficiency, reduces latency, and improves redundancy, making Anycast ideal for distributed services.
One of the most common applications of Anycast is in content delivery networks (CDNs) and Domain Name System (DNS) infrastructure. In CDNs, Anycast allows multiple geographically dispersed servers to share the same IP address. When a client sends a request, the network routes the packet to the server that is topologically closest, ensuring faster response times and reduced load on individual servers. Similarly, Anycast is extensively used in DNS services. Public DNS servers, such as those operated by large providers, often utilize Anycast to ensure that user queries are answered by the closest available server, reducing latency and providing higher availability. In both cases, Anycast inherently provides load distribution and fault tolerance. If one server becomes unavailable, routing protocols automatically redirect traffic to the next closest server, maintaining continuous service without manual intervention.
It is important to distinguish Anycast from other addressing types to understand its unique benefits. Unicast addressing is the simplest form, delivering packets to a single specific device, which makes it unsuitable for scenarios requiring redundancy or load balancing. Multicast addresses are designed for one-to-many communication, sending packets to all devices that have subscribed to a particular group, which differs from Anycast’s one-to-nearest model. Link-local addresses, on the other hand, are automatically assigned to interfaces for communication confined to a single local link, and they cannot be routed across multiple networks. Each of these addressing methods has its use cases, but none provide the specific advantages of Anycast in terms of geographic redundancy and proximity-based routing.
Anycast is particularly valuable in scenarios where low latency, reliability, and distributed service availability are critical. By routing traffic to the nearest device, it minimizes delays caused by long-distance network traversal and reduces congestion on individual servers. Network operators benefit from enhanced scalability, as additional devices can be added to the Anycast group without changing the IP address advertised to clients. Security and resilience are also improved, since traffic can automatically bypass failed nodes or overloaded devices without affecting end users.
In conclusion, Anycast addressing is an advanced networking technique that assigns a single IP address to multiple devices, delivering packets to the nearest device based on routing protocols. Its applications in DNS, CDNs, and other distributed services demonstrate its efficiency, scalability, and resilience. Unlike unicast, multicast, or link-local addresses, Anycast provides a unique combination of proximity-based routing and redundancy. Because the question specifically emphasizes delivery to the nearest device among multiple devices sharing the same address, Anycast is the correct choice, offering a strategic solution for high-performance and reliable network services.
Question 176
Which command tests connectivity and measures round-trip time to a remote host?
A) ping
B) traceroute
C) show ip route
D) show interfaces
Answer: A) ping
Explanation
Ping is one of the most fundamental and widely used network diagnostic tools, providing a simple yet highly effective method for verifying connectivity between devices in an IP network. At its core, ping operates by sending Internet Control Message Protocol (ICMP) echo request packets to a specified target host and then waiting for ICMP echo reply packets. This process allows network administrators and users to determine whether a host is reachable and how long it takes for packets to travel from the source to the destination and back, which is commonly referred to as the round-trip time. The ability to measure latency and detect packet loss makes ping an essential tool for troubleshooting network issues, assessing network performance, and confirming that devices are operational.
When a ping command is issued, the source device generates a small packet containing the ICMP echo request and transmits it toward the target host. If the target device is online and reachable, it responds with an ICMP echo reply. By calculating the time elapsed between sending the request and receiving the reply, ping provides precise latency measurements. These results are particularly useful for diagnosing delays, identifying slow links, and pinpointing connectivity problems within local area networks (LANs) or across wide area networks (WANs). Additionally, repeated ping tests can reveal intermittent connectivity issues or packet loss, which can indicate network congestion, hardware problems, or misconfigurations.
While ping focuses on connectivity and latency, other network commands serve different purposes and do not replace ping’s functionality. Traceroute, for example, maps the path that packets take from the source to the destination by displaying each intermediate hop along the route. While traceroute is useful for diagnosing routing issues and identifying network bottlenecks, it does not provide a straightforward measurement of connectivity to the target host or a simple round-trip timE. Show ip route, another commonly used command, displays the routing table on a network device, showing learned routes, next-hop addresses, and administrative distances. This information is vital for understanding how traffic is directed through the network, but it does not actively test whether a destination host is reachable. Similarly, the show interfaces command provides details about the operational status of interfaces, including errors, bandwidth utilization, and link state, but it does not generate test packets to determine connectivity to a remote host.
Because the primary goal of the question is to verify connectivity and measure round-trip time, ping is the most appropriate tool. Its simplicity, accuracy, and ability to immediately reveal both connectivity and latency make it indispensable for network troubleshooting. Unlike traceroute, show ip route, or show interfaces, ping actively tests the path to a specific host, providing real-time feedback about whether the host is reachable and how efficiently packets traverse the network. For these reasons, when the objective is to confirm connectivity and evaluate round-trip times, ping is the correct and most effective choice. It delivers immediate insight into network health, making it a fundamental tool in the toolkit of any network administrator or engineer.
Question 177
Which protocol is used to map hostnames to IP addresses?
A) DNS
B) DHCP
C) ARP
D) ICMP
Answer: A) DNS
Explanation
DNS (Domain Name System) resolves human-readable hostnames into IP addresses, allowing devices to communicate without remembering numerical addresses.
DHCP dynamically assigns IP addresses to devices but does not translate hostnames.
ARP resolves IP addresses to MAC addresses on a local network.
ICMP is used for diagnostics and error messaging, not for hostname resolution.
Because the question asks about translating hostnames to IP addresses, DNS is correct.
Question 178
Which command displays the next-hop IP address for a specific destination network?
A) show ip route <destination>
B) show interfaces
C) show mac address-table
D) ping
Answer: A) show ip route <destination>
Explanation
Show ip route <destination> provides information about the route to a specific network, including the next-hop IP, administrative distance, and route type.
Show interfaces displays interface status, IP addresses, and statistics but does not provide next-hop routing details.
Show mac address-table displays learned MAC addresses on switch ports, not routing information.
Ping tests connectivity to a host but does not show the next-hop for a route.
Because the question asks for the next-hop to a specific destination network, show ip route <destination> is correct.
Question 179
Which protocol assigns IP addresses dynamically to hosts?
A) DHCP
B) DNS
C) ARP
D) ICMP
Answer: A) DHCP
Explanation
DHCP (Dynamic Host Configuration Protocol) automatically assigns IP addresses, subnet masks, default gateways, and DNS server information to devices, simplifying network management.
DNS resolves hostnames to IP addresses but does not assign IPs.
ARP resolves IP addresses to MAC addresses within a local network.
ICMP is used for diagnostics and error messaging, not for IP address assignment.
Because the question asks about dynamic IP assignment, DHCP is correct.
Question 180
Which type of IPv6 address is automatically assigned for communication on the same link?
A) Link-local
B) Global unicast
C) Multicast
D) Anycast
Answer: A) Link-local
Explanation
Link-local addresses (FE80::/10) are automatically configured on IPv6 interfaces and allow devices to communicate within the same local network segment. They are essential for neighbor discovery and routing protocols.
Global unicast addresses are routable and used for external communication.
Multicast addresses deliver packets to multiple subscribed devices.
Anycast addresses send packets to the nearest device among a set of devices sharing the same address.
Because the question asks for automatic communication on the same link, Link-local is correct.