Cisco 200-301 Cisco Certified Network Associate (CCNA) Exam Dumps and Practice Test Questions Set 9 Q121-135
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Question 121
Which command is used to view the contents of the startup configuration?
A) show startup-config
B) show running-config
C) copy running-config startup-config
D) write memory
Answer: A) show startup-config
Explanation
The Domain Name System, commonly referred to as DNS, is an essential component of modern networking that provides the ability to translate human-readable hostnames into IP addresses. Computers and network devices use IP addresses to identify and communicate with one another across networks, but remembering numerical addresses for each website, server, or device would be impractical for humans. DNS solves this problem by acting as a distributed database that maps descriptive hostnames, such as www.example.com, to their corresponding IP addresses, whether IPv4 or IPv6. This translation allows users to access resources easily without needing to memorize complex numerical strings, enabling intuitive navigation of the internet and local networks.
When a user enters a hostname in a web browser or application, the device sends a DNS query to a DNS resolver. The resolver then searches through a hierarchy of DNS servers, starting from the root servers and moving through top-level domain servers, authoritative servers, and cached entries, to find the IP address that matches the requested hostname. Once the resolver retrieves the correct IP address, it returns it to the device, which can then establish a connection using standard IP communication. This process happens quickly and transparently, allowing seamless access to websites, email servers, and other network services. The efficiency and reliability of DNS are critical for the overall functionality of networked systems, as the vast majority of internet and enterprise applications depend on accurate hostname resolution.
In contrast, the Dynamic Host Configuration Protocol, or DHCP, serves a different purpose in networking. DHCP is responsible for dynamically assigning IP addresses and other network configuration parameters, such as subnet masks, default gateways, and DNS server addresses, to devices on a network. While DHCP ensures that devices can communicate on the network without requiring manual configuration, it does not provide the translation of hostnames into IP addresses. DHCP primarily manages IP allocation and network configuration rather than resolving names for human convenience.
Address Resolution Protocol, or ARP, is another protocol that operates at the local network level. ARP is used to map IP addresses to MAC addresses, which are the hardware identifiers used to deliver packets on a local Ethernet network. ARP is essential for local packet delivery and proper communication between devices on the same subnet, but it does not provide a mechanism for translating hostnames into IP addresses. Its function is entirely different from that of DNS.
ICMP, the Internet Control Message Protocol, is also unrelated to hostname resolution. ICMP is used for network diagnostics and error reporting, allowing devices to send messages about connectivity issues, unreachable hosts, or network congestion. Tools such as ping and traceroute rely on ICMP to measure connectivity and network paths, but ICMP does not convert hostnames to IP addresses.
Because the question specifically asks about translating hostnames into IP addresses, DNS is the correct choice. It uniquely provides the function of mapping human-readable names to numerical addresses, enabling users to access network resources conveniently and reliably. Neither DHCP, ARP, nor ICMP offers this capability, making DNS the essential protocol for hostname resolution in networking.
Question 122
Which type of IPv6 address is automatically assigned for communication within a subnet?
A) Link-local
B) Global unicast
C) Multicast
D) Anycast
Answer: A) Link-local
Explanation
Link-local addresses are a fundamental component of IPv6 networking and are automatically assigned to every IPv6-enabled interface. These addresses fall within the FE80::/10 range and serve a specific purpose: enabling communication between devices on the same local subnet, also known as the local link. Link-local addresses are essential for basic IPv6 operations because they provide a guaranteed way for devices to interact with each other on a subnet without requiring manual configuration or assignment from external servers. This automatic assignment ensures that every IPv6 interface is immediately capable of participating in essential network functions, even before global addresses are configured.
One of the key roles of link-local addresses is supporting neighbor discovery, which is the IPv6 equivalent of the Address Resolution Protocol (ARP) in IPv4. Neighbor discovery allows devices to identify other nodes on the same link, determine their link-layer addresses, and maintain reachability information. Since link-local addresses are automatically present, neighbor discovery can operate immediately upon interface activation, facilitating essential local communication. These addresses also play a crucial role in the operation of certain routing protocols, such as OSPFv3 and EIGRP for IPv6, which use link-local addresses to exchange routing information between directly connected routers. By relying on link-local addresses, these protocols ensure that routing updates and control messages are contained within the local link, enhancing security and stability.
In comparison, global unicast addresses are designed for communication beyond the local link. These addresses are either manually assigned or allocated dynamically through mechanisms such as DHCPv6 and are globally routable on the internet. Global unicast addresses are necessary for accessing external networks, remote hosts, and internet services. However, they are not automatically configured for immediate local communication on the link, nor are they intended for the fundamental neighbor discovery and local routing functions that link-local addresses provide.
Multicast addresses in IPv6 serve a different purpose. They enable one-to-many communication by allowing a single packet to be delivered to multiple devices that have joined a specific multicast group. Multicast addresses are valuable for applications such as streaming media, group messaging, and network service announcements. However, multicast is not used for automatic one-to-one or one-to-all communication within a local link unless devices specifically subscribe to the group, making it unsuitable for default local link communication.
Anycast addresses are assigned to multiple interfaces with the same address, allowing packets to be delivered to the nearest or most optimal device in terms of routing distance. Anycast is commonly used for load balancing and efficient routing, especially in distributed networks. Like multicast, anycast does not provide automatic communication to all devices on the local link and is not assigned by default to every interface.
Because the question specifies automatically assigned addresses for communication within the subnet, link-local addresses are the correct choice. They are inherently configured on every IPv6 interface, enable immediate local link communication, support neighbor discovery, and facilitate routing protocol exchanges. Unlike global unicast, multicast, or anycast addresses, link-local addresses are designed specifically for local subnet communication, making them essential for IPv6 network operations.
Question 123
Which command displays the IP route to a destination network?
A) show ip route <destination>
B) show ip interface brief
C) show mac address-table
D) show arp
Answer: A) show ip route <destination>
Explanation
The command show ip route followed by a specific destination is a fundamental tool in network administration for understanding how a device will forward packets to a particular network. This command provides detailed information about the routing path to the specified destination, including the next-hop IP address, the administrative distance of the route, and the route type, such as whether it is directly connected, static, or learned dynamically through a routing protocol. By examining the output of this command, network administrators can determine the exact path that packets will take to reach a given network, which is crucial for troubleshooting routing issues, verifying configurations, and optimizing network performance. Knowing the next-hop information allows administrators to understand which intermediate devices are involved in forwarding traffic, while administrative distance indicates the trustworthiness of a route relative to other available routes. Route type information helps identify whether the path was learned from a protocol such as OSPF, EIGRP, or RIP, or if it is a manually configured static route. This combination of information is essential for diagnosing misconfigurations or unexpected routing behavior, as it provides a comprehensive view of how traffic flows through the network.
In contrast, show ip interface brief is another widely used command, but it serves a different purpose. This command provides a concise of all interfaces on a network device, displaying key information such as IP addresses assigned to interfaces, their operational status, and whether they are administratively up or down. While this information is valuable for confirming interface connectivity and monitoring the status of physical and logical interfaces, show ip interface brief does not provide any information about the actual routing path to a destination network. It does not indicate which next-hop addresses will be used, nor does it show administrative distances or route types. Therefore, while helpful for interface troubleshooting, it is not suitable for examining network routing decisions.
Show mac address-table is another diagnostic tool, primarily used on switches. It displays the MAC addresses learned on various switch ports, which helps administrators determine where devices are physically connected and monitor Layer 2 network behavior. This command is critical for managing switching environments and for tasks such as port security and VLAN mapping. However, the MAC address table does not contain any Layer 3 routing information and therefore cannot indicate the path packets will take to reach a specific network.
Similarly, show arp displays the mapping of IP addresses to MAC addresses on the local network. ARP is essential for ensuring devices can communicate at Layer 2 and for troubleshooting local connectivity issues. While useful for understanding which physical addresses correspond to IP addresses within the same subnet, show arp does not provide routing information beyond the local link and cannot show the path to a remote network.
Because the question specifically asks for the route to a particular network, the correct command is show ip route followed by the destination network. This command uniquely provides next-hop information, administrative distances, and route types, giving administrators a complete picture of how traffic will be forwarded. Unlike show ip interface brief, show mac address-table, or show arp, show ip route allows for precise analysis of Layer 3 routing behavior, making it the correct choice for understanding how packets will travel across a network to reach a specific destination.
Question 124
Which protocol is used to secure remote administrative access to network devices?
A) SSH
B) Telnet
C) FTP
D) HTTP
Answer: A) SSH
Explanation
Secure Shell, commonly known as SSH, is a network protocol that provides encrypted and secure remote access to network devices, making it an essential tool for network administrators. SSH enables administrators to connect to routers, switches, firewalls, and other devices over an unsecured network while ensuring that all transmitted data, including login credentials and configuration commands, is encrypted. This encryption prevents attackers from intercepting sensitive information such as usernames, passwords, or configuration details, which is critical for maintaining the integrity and security of network infrastructure. By using SSH, administrators can perform configuration changes, monitor device performance, troubleshoot issues, and manage network devices remotely without exposing the network to security risks associated with unencrypted communications. The widespread adoption of SSH in enterprise networks is due to its strong encryption, authentication mechanisms, and support for secure tunneling of administrative sessions, making it a reliable and secure method for device management.
In contrast, Telnet is an older protocol that also allows remote access to network devices, but it transmits all data in plaintext. This lack of encryption means that any information sent over a Telnet session, including administrative credentials and device configuration commands, can be intercepted by attackers using simple packet-sniffing tools. Because of this significant security vulnerability, Telnet is generally considered unsuitable for modern network management, especially in environments where sensitive data must be protected or where compliance standards require secure access methods. While Telnet can still be used in isolated, controlled environments for legacy devices, it is not recommended for production networks due to the high risk of credential compromise.
FTP, or File Transfer Protocol, serves a completely different purpose. FTP is designed to transfer files between devices over a network. While it can be used to upload IOS images, configuration backups, or other files to network devices, FTP does not provide an interactive command-line interface for configuring or managing devices remotely. Furthermore, traditional FTP transmits data in plaintext, which exposes credentials and file contents to potential interception. Therefore, FTP cannot fulfill the requirement of providing secure administrative access.
HTTP, or Hypertext Transfer Protocol, can offer web-based access to some network devices through a browser interface. However, standard HTTP is unencrypted, and any information transmitted—including login credentials and configuration data—can be intercepted. While HTTPS, the encrypted version of HTTP, provides secure web access, many network devices rely on SSH for command-line administration due to its efficiency, encryption strength, and ubiquity in network management practices. Standard HTTP without encryption is not sufficient for secure device administration.
Because the question specifically asks for secure remote administrative access, SSH is the correct protocol. Its encrypted communication, strong authentication mechanisms, and ability to provide a full command-line interface make it uniquely suited for safely managing network devices over potentially unsecured networks. Unlike Telnet, FTP, or standard HTTP, SSH ensures that both credentials and configuration data remain protected, providing administrators with a secure and reliable means of maintaining and controlling network infrastructure.
Question 125
Which type of address is used in IPv4 to reach all hosts on a subnet?
A) Broadcast
B) Unicast
C) Multicast
D) Anycast
Answer: A) Broadcast
Explanation
Broadcast addresses are a fundamental concept in networking that allow a single packet to be delivered to all devices within a specific subnet. Unlike unicast, which is one-to-one communication, broadcast is one-to-all, meaning that every host on the subnet receives the transmitted data. This type of addressing is essential for certain network operations that require all devices to be informed simultaneously. A common example of broadcast communication is the Address Resolution Protocol (ARP). When a device needs to determine the MAC address corresponding to a particular IP address within the same subnet, it sends an ARP request to the broadcast address. Every host on the subnet receives the request, but only the device with the matching IP address responds with its MAC address. This process enables proper communication at the data link layer and ensures that devices can correctly deliver frames within the subnet.
Broadcast addresses are also used for network-wide announcements and certain discovery protocols. For instance, some services use broadcast messages to notify all devices on a subnet of the presence of a server or resource, facilitating automatic detection and configuration. Because the broadcast packet reaches every host, it eliminates the need for sending multiple individual messages, which would be inefficient and increase network traffic. This one-to-all characteristic makes broadcast addressing indispensable for scenarios where information must be disseminated to all connected devices in a subnet simultaneously.
In comparison, unicast addresses are intended for one-to-one communication between a sender and a single recipient. Each packet is directed to a specific device, identified by its unique IP address. While unicast is ideal for routine communication such as web browsing, email delivery, or file transfers, it does not provide a mechanism for reaching multiple devices at once. Using unicast to achieve the same goal as a broadcast would require sending individual packets to every device, resulting in increased bandwidth usage and network overhead. Therefore, unicast cannot replace broadcast when the requirement is to inform all hosts on a subnet simultaneously.
Multicast addresses, on the other hand, are used for one-to-many communication, but only to a predefined group of subscribers. Devices must explicitly join a multicast group to receive the messages. Multicast is highly efficient for applications such as streaming video, audio, or other services where the same data must reach multiple but not necessarily all devices. Unlike broadcast, multicast does not send packets to every host indiscriminately, which is advantageous in large networks but does not fulfill the requirement of delivering data to all hosts in a subnet.
Anycast addresses serve a different purpose entirely. They are assigned to multiple devices, and packets sent to an anycast address are delivered to the nearest device, according to routing metrics. Anycast is commonly used for load balancing and redundancy, ensuring that traffic reaches the closest or most optimal node. While useful in distributed services, anycast does not provide a one-to-all delivery mechanism and is therefore not suitable when the goal is to reach every host on a subnet.
Because the question specifically asks about reaching all hosts on a subnet, the correct addressing method is broadcast. It is uniquely designed to ensure that every device within the subnet receives the transmitted packet, making it essential for ARP, network announcements, and any scenario requiring one-to-all communication. Unlike unicast, multicast, or anycast, broadcast guarantees delivery to every host on the local network, providing a simple and efficient way to disseminate information across a subnet.
Question 126
Which command shows all VLANs configured on a switch?
A) show vlan brief
B) show running-config
C) show interfaces
D) show ip route
Answer: A) show vlan brief
Explanation
The command show vlan brief is widely recognized as one of the most practical and efficient tools for quickly reviewing VLAN configurations on a network switch. When working with switches—especially in environments where many VLANs are configured—it is essential to have a clear, concise way to verify that each VLAN exists, is assigned the correct ID, carries the proper name, and is currently active. The show vlan brief command meets all of these needs by presenting a summarized view that is easy to interpret, even when dealing with large and complex configurations. It allows network administrators to immediately confirm whether VLANs are properly set up, correctly numbered, and functioning as intended. This is particularly helpful when troubleshooting connectivity issues or validating newly applied configurations.
In addition to VLAN IDs and names, show vlan brief also displays the status of each VLAN. This means an administrator can quickly see whether a VLAN is active or inactive, helping to pinpoint potential issues caused by misconfigurations or disabled VLANs. By providing an organized and readable, this command eliminates the need to sift through long and detailed configuration files. Its simplicity and clarity make it the preferred command when the main goal is to confirm the presence and health of all VLANs on a switch.
On the other hand, the show running-config command contains a much more comprehensive view of the device’s active configuration. While it does include VLAN information, it is not optimized for quickly reviewing VLANs in a structured or summarized format. Instead, it presents VLAN data embedded among many other configuration details, such as interface settings, security parameters, spanning-tree options, routing configurations, and other switch features. Searching through this lengthy output to locate VLAN specifics can be time-consuming and inefficient, especially when you only need to verify VLAN IDs, names, and operational status. For this reason, while show running-config is extremely valuable for deeper configuration review, it is not the most effective command when the objective is simply to check all VLANs at a glance.
The show interfaces command is also useful in network troubleshooting, but it serves a different purpose. This command focuses on the status, speed, duplex, and operational details of individual interfaces rather than VLAN-wide information. While it may display which VLAN a specific interface belongs to, it does not provide an overall of every VLAN configured on the switch. Instead, it is intended to help diagnose problems related to physical links, interface errors, or traffic-related issues. Because of this, it is not suitable when the requirement is to see all VLANs on the device.
Similarly, the show ip route command is not designed to provide VLAN data. Its function is to display the routing table, showing how packets will be forwarded through the network. It includes information about connected networks, static routes, and dynamic routing protocol entries. Since VLANs are a Layer 2 construct, they do not appear in the routing table unless they are associated with Layer 3 interfaces. Therefore, this command offers no meaningful insight into VLAN configuration.
Question 127
Which type of IPv6 address identifies a single interface for one-to-one communication?
A) Unicast
B) Multicast
C) Anycast
D) Link-local
Answer: A) Unicast
Explanation
Unicast addresses play a fundamental role in network communication because they are designed specifically for one-to-one interactions between devices. When a device sends a packet to a unicast address, that packet is intended for one unique destination. Only the interface assigned to that address will receive and process the data. This makes unicast communication the most direct and individualized method of data transmission across a network. It ensures that information is delivered precisely where it is intended without broadcasting to unnecessary devices or consuming excess network resources. Unicast addressing is commonly used in everyday activities such as browsing websites, accessing servers, or communicating with specific hosts, where the communication is focused on a single, unique endpoint.
In contrast to unicast, multicast addresses serve a different purpose. Multicast communication is designed to deliver packets to multiple devices that have explicitly joined a multicast group. Instead of sending individual copies of the same data to every device, multicast transmits a single stream that is replicated only where necessary. This approach is particularly efficient for applications like video streaming, online conferences, or real-time data distribution, where the same content needs to reach many receivers simultaneously. Even though multicast is more efficient for group communication, it does not provide the one-to-one specificity required when the question is about direct communication between two devices.
Another related concept is anycast addressing, which also involves multiple devices but behaves differently from multicast. With anycast, the same address is assigned to multiple interfaces, often located in different geographical regions or network locations. When a packet is sent to an anycast address, the network delivers it to the nearest or most optimal device based on routing metrics. This approach is useful for improving performance, reducing latency, and enhancing redundancy. Services like DNS or global content distribution often rely on anycast because it allows clients to connect to the closest available server. However, anycast still does not represent true one-to-one communication, since the address corresponds to a set of devices rather than a single unique destination.
Link-local addresses also differ significantly from unicast addresses intended for general network communication. Link-local addressing is used strictly within a local network segment and cannot be routed beyond that local link. These addresses are automatically generated by devices for purposes such as neighbor discovery or local communication without requiring manual configuration or a DHCP server. While link-local addresses may still support one-to-one communication within a local segment, they are limited in scope and do not represent the broader, routable one-to-one communication typically referenced when discussing unicast addressing.
Considering the distinctions among unicast, multicast, anycast, and link-local addressing, the only type of address that reliably provides pure one-to-one communication across networks is the unicast address. It uniquely identifies a single interface and ensures that packets reach only the intended device, making it the correct choice when the requirement is specifically one device communicating directly with another without involving groups, nearest-node delivery, or limited-scope addressing.
Question 128
Which command tests connectivity to a remote host?
A) ping
B) traceroute
C) show ip route
D) show interfaces
Answer: A) ping
Explanation
The ping command is one of the simplest yet most valuable tools available to network administrators and anyone troubleshooting network connectivity issues. Its primary function is to send ICMP echo request messages to a target device and wait for ICMP echo replies. By doing this, ping verifies whether communication between the source and the destination is possible. If replies are received consistently, it confirms that the remote host is reachable and that the path between the two devices is functioning. Additionally, ping measures round-trip time, allowing users to evaluate how long it takes for packets to travel to the destination and back. This helps identify latency issues and can offer early hints about potential congestion, routing problems, or degraded network performance. Because of its simplicity and immediate feedback, ping remains one of the first tools used when diagnosing connectivity problems.
Traceroute, while also a diagnostic tool, serves a different purpose. Instead of simply verifying whether a destination is reachable, traceroute maps the path that packets take across a network. It reveals each hop along the route, showing where delays occur or where packets may be dropped. This makes traceroute extremely helpful for identifying routing loops, pinpointing problematic routers, or understanding how traffic flows through a complex network. However, it does not serve as a basic connectivity test in the same way ping does. Traceroute focuses on path discovery rather than simple reachability, and for this reason, it is not the best answer when a question specifically asks how to test whether a device can communicate with a remote host.
The show ip route command offers yet another type of information. Instead of testing communication actively, it displays the device’s routing table, showing networks the router knows about, how to reach them, and which next-hop devices are used. This is essential for troubleshooting routing issues, verifying routing protocols, and understanding how network paths are determined. However, simply having an entry in the routing table does not guarantee that the path is functional. A route may exist, but a link could be down, a neighboring router could be unreachable, or there could be issues with forwarding traffic. Because show ip route provides routing information rather than testing connectivity, it cannot confirm whether a device can successfully reach a remote host.
Similarly, the show interfaces command provides detailed information about local interface status, throughput, errors, and other operational statistics. It is invaluable when diagnosing physical-layer or data-link-layer problems, such as interface drops, speed mismatches, or excessive errors. However, it does not test communication beyond the local device. It tells nothing about the reachability of remote hosts. Even if all interfaces appear to be functioning correctly, connectivity to another network or device might still fail due to issues elsewhere in the path.
Since the question focuses specifically on verifying connectivity to another device, the ping command is the most appropriate tool. It directly tests reachability, provides immediate feedback, and measures response times, making it the most effective way to confirm whether communication with a remote host is possible.
Question 129
Which protocol provides one-to-nearest communication among multiple devices sharing the same address?
A) Anycast
B) Unicast
C) Multicast
D) Broadcast
Answer: A) Anycast
Explanation
Anycast addressing is a unique method in networking that allows a single IP address to be assigned to multiple devices, typically distributed across different physical locations or network segments. When a device sends a packet to an anycast address, the network determines which instance of the address is closest or most optimal based on routing metrics, and the packet is delivered to that specific device. This approach effectively allows one-to-nearest communication, where the “nearest” device is defined in terms of network distance, cost, or other routing criteria rather than physical proximity alone. Anycast is particularly useful for improving performance, reducing latency, and enhancing reliability for services that are globally distributed or need to handle high volumes of requests efficiently.
A common and well-known application of anycast addressing is in Domain Name System (DNS) services. Large-scale DNS providers often deploy multiple servers worldwide and assign the same IP address to all of them. When a client queries the DNS service, the network routes the request to the closest server, ensuring a fast response and balancing the load across all servers. This mechanism not only improves user experience by minimizing latency but also adds resilience. If one server becomes unreachable due to failure or maintenance, the routing protocols automatically direct traffic to the next closest server using the same anycast address. This capability makes anycast indispensable for distributed network services that prioritize speed, reliability, and redundancy.
To understand the distinct role of anycast, it is helpful to compare it with other addressing methods. Unicast addresses are assigned to a single interface and support one-to-one communication, where packets are delivered to a specific device. This is ideal for direct communication but does not provide the benefits of routing to the nearest available resource among multiple devices. Multicast addresses, in contrast, allow one-to-many communication where a packet is sent to a group of subscribed devices. Multicast is efficient for distributing the same data, such as video streams or software updates, to multiple recipients simultaneously, but it does not provide the concept of nearest-node delivery. Broadcast addresses operate differently by sending packets to all devices within a local subnet. Broadcast is effective for scenarios like network discovery or address resolution, but it is limited in scope and indiscriminate in delivery, reaching every device regardless of distance or relevance.
Anycast addresses stand out because they combine the idea of a single logical destination with the intelligence of routing to the nearest instance. This makes them particularly suited for services that are replicated across multiple locations, where performance, redundancy, and resource optimization are priorities. Unlike unicast, which targets a single device, anycast ensures that the packet reaches the best possible location. Unlike multicast or broadcast, anycast does not flood multiple devices or rely on subscription; instead, it uses standard routing protocols to determine the optimal endpoint.
Given the specific requirement of one-to-nearest communication, anycast addressing is the correct solution. It ensures that packets are efficiently delivered to the closest instance of multiple devices sharing the same address, providing both speed and reliability while optimizing network resources. Its use in distributed services, global content delivery, and critical network infrastructure highlights its significance and practicality in modern networking.
Question 130
Which protocol maps IP addresses to MAC addresses on a local network?
A) ARP
B) DNS
C) DHCP
D) ICMP
Answer: A) ARP
Explanation
The Address Resolution Protocol, commonly known as ARP, plays a critical role in IPv4 networking by enabling devices to map IP addresses to their corresponding MAC addresses. In local area networks, devices communicate using MAC addresses at the data link layer, but applications and higher-layer protocols typically operate using IP addresses. ARP acts as the bridge between these layers, allowing devices to determine the physical hardware address that corresponds to a given IP address. When a device needs to send a packet to another device within the same subnet, it uses ARP to query the network and retrieve the MAC address associated with the destination IP. Once the MAC address is known, the device can properly encapsulate the packet in a frame and deliver it across the local network. This functionality is essential for successful data delivery within Ethernet and other similar local networks, making ARP a foundational protocol for IPv4 communications.
Other protocols, while crucial to networking, serve entirely different purposes. The Domain Name System, or DNS, is used for translating human-readable hostnames into IP addresses. DNS enables users to enter a website name such as www.example.com and have it resolved into an IP address that routers and devices can use for communication. DNS does not, however, provide any information about MAC addresses or assist with local delivery of packets within a subnet. Its role is limited to the logical mapping between names and IP addresses, rather than bridging the gap between IP and hardware addresses.
The Dynamic Host Configuration Protocol, or DHCP, also serves a distinct function. DHCP automates the process of assigning IP addresses to devices on a network, allowing them to join and communicate without requiring manual configuration. While DHCP is instrumental in managing address allocation and ensuring devices have valid IP addresses, it does not perform any mapping between IP addresses and MAC addresses. Its purpose is strictly to facilitate dynamic addressing and configuration rather than resolving addresses for local packet delivery.
The Internet Control Message Protocol, ICMP, is primarily used for diagnostic and error-reporting purposes. Tools such as ping and traceroute rely on ICMP to test connectivity and measure network performance. ICMP messages can indicate when a destination is unreachable or when packets are dropped along a route. While ICMP is invaluable for network troubleshooting, it does not provide address resolution capabilities, nor does it map IP addresses to MAC addresses for local delivery.
Given the functions of these protocols, it is clear that when the goal is to determine the MAC address corresponding to a specific IPv4 address, ARP is the correct choice. Its purpose is explicitly designed to translate IP addresses into the hardware addresses required for proper packet delivery within a local network. This makes ARP indispensable for local communication and ensures that devices can successfully identify and reach their intended destinations using the underlying network hardware. By contrast, DNS, DHCP, and ICMP, while essential in their own domains, do not provide this IP-to-MAC resolution functionality.
Question 131
Which command displays all the routes learned via OSPF?
A) show ip route ospf
B) show ip route eigrp
C) show running-config
D) show interfaces
Answer: A) show ip route ospf
Explanation
The command show ip route ospf is an essential tool for network administrators working with OSPF, the Open Shortest Path First routing protocol. This command displays all routes that a router has learned through OSPF, providing crucial information about the destination networks, the next-hop addresses, and the administrative distances associated with each route. By using this command, administrators can quickly verify that OSPF is functioning correctly and that the network is routing traffic as expected. The output allows a concise view of the OSPF-learned routes, showing which networks are reachable via OSPF, the path that packets will take, and whether the routes are active and usable. This level of visibility is critical for troubleshooting, validating network topology, and ensuring proper route propagation throughout an OSPF-enabled network.
In contrast, the command show ip route eigrp serves a different purpose. It displays only the routes that the router has learned through the EIGRP protocol, which is another dynamic routing protocol. While EIGRP is a powerful protocol, its output does not include routes learned through OSPF. Therefore, if the goal is to examine OSPF-learned routes specifically, show ip route eigrp would not provide the information required. Using it in this context would be ineffective because it focuses exclusively on EIGRP routes and ignores any OSPF information.
The show running-config command, on the other hand, provides a complete view of the router’s current active configuration stored in RAM. This includes all routing protocol configurations, interface settings, access control lists, and other device parameters. While show running-config does contain OSPF configuration details such as network statements, area assignments, and interface participation, it does not display the actual routes that OSPF has learned from its neighbors. It only shows how the routing protocol has been configured, not the real-time routing table information. For verifying route propagation and ensuring that OSPF has correctly learned and installed routes, show running-config is insufficient.
Similarly, the show interfaces command provides detailed information about the router’s interfaces, including statistics, operational status, IP addresses assigned to interfaces, and error counters. Although this information is helpful for troubleshooting interface-related issues, it does not include any routing information. It cannot show which networks are reachable, the next-hop addresses, or the administrative distance of routes. Therefore, it is not suitable for verifying OSPF-learned routes or diagnosing routing-related problems.
Because the question specifically focuses on verifying routes learned through OSPF, the correct command is show ip route ospf. This command directly addresses the need to see the OSPF routing table, providing a clear, concise view of all networks that OSPF has advertised and learned. By displaying this information, administrators can confirm proper OSPF operations, troubleshoot routing issues, and ensure that traffic is being forwarded along the expected paths. Unlike commands that display configuration, interface statistics, or routes learned by other protocols, show ip route ospf gives precise, actionable information about OSPF-learned routes, making it the definitive choice for this task.
Question 132
Which protocol provides dynamic IP address assignment to hosts?
A) DHCP
B) DNS
C) ARP
D) ICMP
Answer: A) DHCP
Explanation
DHCP dynamically assigns IP addresses, subnet masks, default gateways, and DNS server information to hosts on a network. It reduces manual configuration errors and ensures proper IP address management.
DNS resolves hostnames to IP addresses but does not assign IP addresses.
ARP maps IP addresses to MAC addresses within a local network.
ICMP is used for diagnostics and error reporting, not for IP assignment.
Because the question asks for dynamic IP address assignment, DHCP is correct.
Question 133
Which command shows the MAC address associated with each switch port?
A) show mac address-table
B) show arp
C) show ip interface brief
D) show running-config
Answer: A) show mac address-table
Explanation
Show mac address-table displays all MAC addresses learned by a switch and the interfaces on which they were learned. This is crucial for troubleshooting connectivity issues and verifying proper switch operation.
Show arp displays IP-to-MAC mappings but not the port association.
Show ip interface brief displays interface IP addresses and status, not MAC address information.
Show running-config displays the active configuration of the device, not the learned MAC addresses.
Because the question asks specifically about MAC addresses and associated ports, show mac address-table is correct.
Question 134
Which type of IPv6 address allows one-to-one communication?
A) Unicast
B) Multicast
C) Anycast
D) Link-local
Answer: A) Unicast
Explanation
Unicast addresses in IPv6 identify a single interface and allow one-to-one communication. This is the standard method for device-to-device communication.
Multicast addresses deliver packets to all devices in a subscribed group.
Anycast addresses deliver packets to the nearest device among a set of devices sharing the same address.
Link-local addresses are automatically assigned for communication on the same link only.
Since the question asks for one-to-one communication, Unicast is correct.
Question 135
Which command displays interface statistics including errors and collisions?
A) show interfaces
B) show ip route
C) show mac address-table
D) show arp
Answer: A) show interfaces
Explanation
Show interfaces provides detailed information about each interface, including operational status, IP addresses, errors, and collisions. This is vital for troubleshooting performance issues on a network.
Show ip route displays routing information but not interface statistics.
Show mac address-table displays MAC addresses and associated ports but not interface errors.
Show arp displays IP-to-MAC mappings but does not provide interface statistics.
Because the question asks about interface statistics, show interfaces is correct.