Cisco 200-301 Cisco Certified Network Associate (CCNA) Exam Dumps and Practice Test Questions Set 15 Q211-225
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Question 211
Which type of VLAN carries untagged traffic on a trunk port?
A) Native VLAN
B) Data VLAN
C) Voice VLAN
D) Management VLAN
Answer: A) Native VLAN
Explanation
In Ethernet networking, VLANs, or Virtual Local Area Networks, are used to segment network traffic logically, even if devices are physically connected to the same switch. VLANs help improve security, reduce broadcast domains, and organize networks according to function or department. When it comes to VLANs on switches, trunk ports play a crucial role in carrying traffic for multiple VLANs across a single physical link. Trunk ports are commonly used between switches or between a switch and a router to allow multiple VLANs to communicate over the same connection. Since trunk links carry traffic from more than one VLAN, there must be a method to distinguish which VLAN each frame belongs to, and this is achieved using VLAN tagging.
VLAN tagging works by adding a small header to Ethernet frames, indicating the VLAN ID. Most traffic traversing a trunk port is tagged to ensure it is associated with the correct VLAN on the receiving switch. However, there are situations where frames do not carry VLAN tags. Untagged traffic can come from legacy devices or from ports where VLAN tagging is not configured. To handle these untagged frames on a trunk port, the concept of a native VLAN is introduced. The native VLAN is a specific VLAN assigned to a trunk port so that any untagged traffic arriving at the trunk port is automatically associated with that VLAN. This ensures that devices that do not support VLAN tagging can still communicate over the network without issues, maintaining compatibility with a wide range of equipment.
Other types of VLANs serve different purposes. A data VLAN is typically assigned to access ports, which are ports connected to standard end-user devices such as computers, printers, or workstations. Data VLANs carry normal user traffic, ensuring it is isolated from other types of traffic and improving network organization. Voice VLANs are dedicated to IP phone traffic. These VLANs often include Quality of Service (QoS) configurations to prioritize voice traffic, ensuring clear and uninterrupted communication even when the network is congested. The separation of voice traffic from standard data traffic helps maintain call quality and network efficiency.
Management VLANs are reserved for administrative traffic used by network administrators to manage network devices. This includes traffic generated by protocols such as SSH, SNMP, or Telnet, which provide remote access and monitoring capabilities. By isolating management traffic from user and voice traffic, organizations enhance security, reduce congestion, and maintain better control over network devices.
Because the question specifically asks about handling untagged traffic on a trunk port, the native VLAN is the correct answer. It is uniquely designed for this purpose, ensuring that any frame arriving at the trunk without a VLAN tag is placed in the correct VLAN automatically. This prevents communication failures between devices that do not tag their traffic and maintains consistent network operation. The assignment of a native VLAN to a trunk port is therefore essential in networks that include both tagged and untagged devices, providing seamless integration and compatibility.
Overall, the native VLAN plays a critical role in trunk port configurations by bridging the gap between tagged and untagged traffic. While data, voice, and management VLANs serve specialized functions for user traffic, voice communication, and administrative operations, only the native VLAN addresses the challenge of untagged frames on trunk links, making it an indispensable part of VLAN design and switch configuration.
Question 212
Which command displays all DHCP leases on a Cisco device?
A) show ip dhcp binding
B) show ip interface brief
C) show running-config
D) show arp
Answer: A) show ip dhcp binding
Explanation
Show ip dhcp binding lists all IP addresses leased to clients, including their MAC addresses, lease durations, and associated interfaces.
Show ip interface brief displays interface IP addresses and status but not DHCP leases.
Show running-config shows the active configuration but does not display current DHCP leases.
Show arp displays IP-to-MAC mappings but not DHCP lease information.
Because the question asks for active DHCP leases, show ip dhcp binding is correct.
Question 213
Which type of IPv4 address is used for one-to-one communication?
A) Unicast
B) Broadcast
C) Multicast
D) Anycast
Answer: A) Unicast
Explanation
In networking, addressing methods are fundamental for determining how data is delivered across a network. The type of address used directly affects how packets travel from a sender to a receiver, and understanding these methods is essential for efficient network design and troubleshooting. Among the various types of network addresses, unicast, broadcast, multicast, and anycast are commonly used, each serving a specific purpose based on the intended scope of communication.
Unicast addressing is the most straightforward and widely used method in networking. It involves one-to-one communication, where a single sender transmits data directly to a specific recipient device identified by its unique address. When a device sends a unicast packet, it includes the recipient’s MAC address at the data link layer or IP address at the network layer, ensuring that only the intended recipient receives the data. This method is efficient when the communication is targeted and private, such as sending a file to a colleague’s computer, accessing a web server, or performing remote management tasks. Because unicast communication is point-to-point, it minimizes unnecessary network traffic and reduces the chances of congestion that can occur when data is sent to multiple devices unnecessarily.
In contrast, broadcast addressing is used when communication must reach all devices within a particular subnet. A broadcast packet is transmitted to every device in the network segment, regardless of whether it needs the information. This approach is useful for scenarios such as ARP requests, where a device needs to discover the MAC address of another device on the same subnet, or sending network announcements. However, because broadcast traffic is received by every device, excessive broadcasts can lead to network congestion, and administrators typically limit broadcast usage to essential functions.
Multicast addressing is designed for one-to-many communication, targeting only a group of devices that have expressed interest in receiving specific traffic. Devices join multicast groups to subscribe to the data they require. Multicast is commonly used for applications like video streaming, live broadcasts, and software distribution, where sending separate unicast streams to each recipient would be inefficient. By sending a single stream to a multicast group, network bandwidth is conserved while still reaching multiple recipients effectively.
Anycast addressing, on the other hand, is used for one-to-nearest communication in which packets are delivered to the closest device among a set of devices sharing the same IP address. This method is often implemented in content delivery networks (CDNs) or distributed services to ensure clients receive responses from the nearest server, reducing latency and improving performance. Anycast is more specialized and typically employed in large-scale networks to optimize access to services.
Because the question specifically asks about communication with a single device, unicast addressing is the correct choice. Unlike broadcast, multicast, or anycast, unicast ensures that data is sent directly and exclusively to the intended recipient, making it ideal for private, targeted communications. Unicast addresses are foundational in everyday network operations, supporting essential services such as web access, email, file transfers, and secure remote connections.
Uunicast provides direct, one-to-one communication between devices, ensuring efficient and reliable delivery of data. While broadcast, multicast, and anycast serve important purposes for broader or optimized delivery, unicast remains the primary method for individual device communication, highlighting its significance in network design and operation.
Question 214
Which command shows all VLANs configured on a Cisco switch?
A) show vlan brief
B) show running-config
C) show interfaces
D) show mac address-table
Answer: A) show vlan brief
Explanation
Show vlan brief provides a concise list of VLANs on a switch, including VLAN IDs, names, and status. It is useful for quickly verifying VLAN configuration.
Show running-config displays the full configuration but is less concise for checking VLANs.
Show interfaces displays interface status and IP assignments but not VLAN summaries.
Show mac address-table displays learned MAC addresses and ports, not VLANs.
Because the question asks about all VLANs configured, show vlan brief is correct.
Question 215
Which command displays all routes learned via OSPF?
A) show ip route ospf
B) show ip route eigrp
C) show ip protocols
D) show running-config
Answer: A) show ip route ospf
Explanation
Show ip route ospf lists all routes learned through OSPF, including destination networks, next-hop addresses, and administrative distance.
Show ip route eigrp displays routes learned via EIGRP, not OSPF.
Show ip protocols displays routing protocol configurations and timers but not specific learned routes.
Show running-config shows the active configuration but does not list dynamically learned routes.
Because the question asks for OSPF-learned routes, show ip route ospf is correct.
Question 216
Which command displays the currently active configuration on 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
Show running-config displays the configuration currently stored in RAM, reflecting all changes since the last reload.
Show startup-config displays the saved configuration in NVRAM.
Copy running-config startup-config saves the running configuration to NVRAM but does not display it.
Show version shows device hardware, software version, and uptime but not configuration details.
Because the question asks for the current active configuration, show running-config is correct.
Question 217
Which type of IPv6 address is used for one-to-one communication?
A) Unicast
B) Multicast
C) Anycast
D) Link-local
Answer: A) Unicast
Explanation
n networking, the method by which data is addressed and delivered across a network is crucial for ensuring efficient and accurate communication between devices. Network addresses are designed to specify the intended recipients of data packets, and understanding the different types of addresses is fundamental for network design, troubleshooting, and optimization. Among the most commonly used addressing methods are unicast, multicast, anycast, and link-local addresses. Each of these types serves a specific purpose depending on the scope and target of communication.
Unicast addressing is the most basic and widely used form of network communication. It is a one-to-one communication method, where a single sender transmits data directly to a specific recipient identified by a unique address. This ensures that only the intended device receives the information, making it ideal for private and targeted communication. Unicast addresses are typically assigned to individual network interfaces, allowing each device on a network to be uniquely identified. Common use cases for unicast addressing include sending emails, accessing web pages, transferring files, or performing remote device management. Because unicast delivers data to a single destination, it minimizes unnecessary traffic on the network and reduces congestion compared to other communication methods that target multiple devices.
Multicast addressing, in contrast, is used for one-to-many communication. This type of addressing allows a single sender to transmit data to multiple devices that have expressed interest in receiving the data, usually by joining a specific multicast group. Multicast is commonly used in applications such as video conferencing, streaming media, and real-time data distribution, where multiple recipients need to receive the same information simultaneously. By sending a single stream of data to all members of a multicast group, network efficiency is improved, as it avoids sending multiple copies of the same data to each recipient individually.
Anycast addressing is a method in which data is delivered to the nearest or most optimal device among multiple devices sharing the same address. Anycast is often used in distributed services, such as content delivery networks or global DNS servers, where requests are routed to the closest available server to reduce latency and improve performance. While anycast provides one-to-one communication in practice, the selection of the recipient is determined by the network rather than a specific device chosen by the sender.
Link-local addresses are automatically assigned to devices for communication within a single network segment or link. These addresses are useful for local network operations, such as neighbor discovery and automatic address configuration. Link-local communication does not require routing and is restricted to a single link, which makes it unsuitable for broader one-to-one communication across multiple network segments.
Because the question specifically asks about one-to-one communication, unicast addressing is the correct choice. Unlike multicast, which targets multiple devices, anycast, which delivers to the nearest device among several, or link-local addresses, which are limited to a local link, unicast ensures that data is transmitted directly to a single, specific device. This direct delivery method is foundational for most everyday network interactions, supporting private, reliable, and efficient communication between devices.
Uunicast provides precise, one-to-one communication in a network, ensuring that data reaches the intended recipient without unnecessary distribution to other devices. While other addressing methods such as multicast, anycast, and link-local addresses serve specialized purposes for group communication, proximity-based delivery, or local link operations, unicast remains the primary method for direct device-to-device communication, highlighting its essential role in network operations.
Question 218
Which type of VLAN is used for administrative traffic such as SSH or SNMP?
A) Management VLAN
B) Voice VLAN
C) Data VLAN
D) Native VLAN
Answer: A) Management VLAN
Explanation
In network design, VLANs, or Virtual Local Area Networks, are essential for logically segmenting network traffic, improving security, and enhancing performance. VLANs allow administrators to group devices based on function, department, or traffic type, even if the devices are physically connected to the same switch. This segmentation ensures that different types of traffic can coexist on the same network infrastructure without interfering with one another, providing better control and organization of network resources. Among the various types of VLANs, the management VLAN plays a critical role in maintaining the security and accessibility of network devices for administrative purposes.
A management VLAN is specifically dedicated to administrative traffic, which includes communication between network devices and administrators. This traffic often consists of protocols and tools used for device management, such as SSH, Telnet, SNMP, and web-based management interfaces. By isolating administrative traffic in its own VLAN, organizations can prevent regular user traffic or voice traffic from mixing with management communications. This separation is crucial for security, as it limits the exposure of sensitive management interfaces to only those devices and users that are authorized. It also allows network administrators to monitor and control administrative traffic more effectively, ensuring that configuration changes, monitoring, and troubleshooting activities are performed securely and efficiently.
In contrast, other VLAN types serve different purposes. A voice VLAN is dedicated to IP phone traffic, which is often prioritized using Quality of Service (QoS) settings to ensure clear and uninterrupted voice communication. By isolating voice traffic from regular data traffic, networks can reduce latency and packet loss for voice calls, enhancing call quality. Data VLANs carry regular user traffic, such as computers, printers, and other end-user devices, ensuring that general network communication is segmented from voice and management traffic. This segmentation improves performance and security by keeping different traffic types separate.
The native VLAN is another concept often associated with trunk ports. It handles untagged traffic that passes through a trunk link connecting switches or other network devices. While the native VLAN ensures compatibility with devices that do not support VLAN tagging, it is not intended for specialized traffic types such as administrative or voice traffic. Its primary function is to provide a default VLAN for frames that do not carry a VLAN tag, maintaining proper communication across trunk links.
Because the question specifically asks about administrative traffic, the management VLAN is the correct choice. It is uniquely designed to carry sensitive management communications, keeping them isolated from other types of network traffic. This isolation not only enhances security by restricting access to management interfaces but also simplifies monitoring and troubleshooting by centralizing administrative traffic within a dedicated VLAN. Network administrators can use this VLAN to perform configuration changes, monitor device performance, and implement security policies without interference from user or voice traffic.
The management VLAN is a critical component of network design that ensures administrative traffic is secure, accessible, and efficiently managed. While voice VLANs, data VLANs, and native VLANs serve specific functions for voice communication, user traffic, and untagged frames, only the management VLAN addresses the need for dedicated administrative traffic. By creating this separation, organizations enhance both security and operational efficiency, making the management VLAN an essential element in professional network environments.
Question 219
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
Show ip dhcp binding lists all IP addresses leased to clients, along with their MAC addresses, lease times, and associated interfaces.
Show ip interface brief shows interface IPs and status but not DHCP leases.
Show running-config displays active configuration but not DHCP leases.
Show arp displays IP-to-MAC mappings but not DHCP lease information.
Because the question asks for leased IP addresses, show ip dhcp binding is correct.
Question 220
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 method in which the same IP address is assigned to multiple devices across a network, and traffic destined for that address is routed to the nearest or most optimal device based on routing metrics. This approach allows multiple servers or nodes to share the same address while providing services efficiently and reliably to clients. Anycast is particularly valuable in distributed networks and large-scale services such as Domain Name System (DNS) servers, content delivery networks (CDNs), and distributed web services, where it is crucial to reduce latency and ensure fast responses for users in different geographic locations.
The fundamental concept of anycast is that multiple devices advertise the same IP address in the routing system, but routing protocols determine which device is “closest” in terms of network topology. When a client sends a packet to an anycast address, the network infrastructure forwards the packet to the nearest device according to metrics such as hop count, link cost, or delay. This mechanism ensures that clients automatically receive responses from the most accessible node, improving performance and reducing the load on individual servers. Anycast also enhances redundancy; if one device fails, the routing protocols automatically direct traffic to another device advertising the same anycast address, providing resilience and high availability without requiring manual intervention.
Anycast addresses differ significantly from other common types of network addressing. Unicast addresses are designed for one-to-one communication, where a single source sends packets directly to a single destination device. This ensures precise delivery, but it does not provide the load-balancing or geographic optimization benefits that anycast offers. Multicast addresses are used to deliver packets to multiple devices that have explicitly subscribed to a multicast group. This one-to-many approach is suitable for streaming media or group notifications but does not prioritize delivery to the nearest recipient. Link-local addresses are automatically assigned to interfaces for communication within the same local link or subnet. They are essential for functions such as neighbor discovery in IPv6, but their scope is limited to a single link and cannot be used for geographically distributed services.
Anycast is widely applied in large-scale network services due to its efficiency, scalability, and reliability. For example, in the DNS system, root servers and authoritative name servers are often deployed with anycast addresses. Users querying the DNS system are automatically routed to the nearest available server, minimizing latency and improving response times globally. Similarly, content delivery networks use anycast to direct user requests to the closest caching server, ensuring faster content delivery while balancing network traffic and reducing the risk of overloading individual servers.
Because the question specifically asks about delivering traffic to the nearest device among multiple devices sharing the same address, anycast is the correct choice. Its ability to provide automatic, topology-aware routing to the closest device makes it an essential tool for distributed services that require low latency, high availability, and efficient load distribution. By leveraging anycast addressing, network administrators can optimize service delivery, improve user experience, and maintain reliable network operations across wide and complex infrastructures. Its combination of scalability, redundancy, and performance optimization distinguishes it from unicast, multicast, and link-local addressing, making anycast uniquely suited for applications that span multiple locations or devices.
Question 221
Which command displays interface statistics such as errors, collisions, and bandwidth utilization?
A) show interfaces
B) show ip interface brief
C) show mac address-table
D) show running-config
Answer: A) show interfaces
Explanation
The show interfaces command is a fundamental tool for network administrators, providing detailed information about each interface on a network device. Unlike commands that give only a high-level overview or focus on configuration, show interfaces delivers a comprehensive view of the operational state and performance of each interface, making it invaluable for troubleshooting and monitoring network health. The command displays a wide array of metrics, including physical status, protocol status, bandwidth usage, input and output errors, collisions, and other critical performance indicators. By analyzing this information, administrators can identify connectivity issues, performance bottlenecks, hardware failures, and misconfigurations, ensuring reliable and efficient network operation.
When executed, show interfaces provides details for each interface, starting with the operational status, which indicates whether the interface is physically up and whether the line protocol is functioning correctly. This distinction is crucial because an interface might be physically connected but administratively down or experiencing protocol-level issues. In addition to operational status, the command displays traffic statistics, including the number of packets transmitted and received, the amount of bandwidth utilized, and the presence of errors such as CRC errors, input drops, or collisions. Monitoring these statistics allows administrators to pinpoint congestion points, faulty cables, misbehaving devices, or network segments with high error rates that could affect performance.
Other commands provide related information but do not offer the same depth of interface performance data. For example, show ip interface brief offers a concise of interfaces, displaying IP addresses and the operational status of each interface. While useful for a quick overview or verifying that interfaces are up, it does not provide detailed statistics such as error counts, collisions, or bandwidth usage. Similarly, show mac address-table lists all MAC addresses learned by the switch along with the ports they are associated with, which is helpful for verifying device connectivity or troubleshooting Layer 2 issues, but it does not provide performance statistics or detailed interface metrics. The show running-config command shows the current device configuration stored in RAM, including interface configurations, VLAN assignments, and protocol settings. While this command is critical for understanding how the device is configured, it does not provide real-time statistics or operational data about interface performance.
Because the question specifically asks for interface statistics, the show interfaces command is the correct choice. It provides a detailed, real-time view of each interface’s status and performance, enabling administrators to identify and resolve issues that may impact network connectivity, throughput, or reliability. By reviewing the metrics provided by this command, network professionals can detect interface errors, monitor traffic patterns, ensure proper bandwidth utilization, and maintain overall network health. The comprehensive information offered by show interfaces makes it an indispensable tool for troubleshooting, performance monitoring, and proactive network management, allowing administrators to maintain efficient, reliable, and high-performing network operations across all devices and interfaces.
Question 222
Which protocol allows devices to automatically learn IP-to-MAC address mappings?
A) ARP
B) DNS
C) DHCP
D) ICMP
Answer: A) ARP
Explanation
Address Resolution Protocol, commonly known as ARP, is a critical protocol in networking that enables devices to communicate within a local area network by mapping IP addresses to their corresponding MAC addresses. In Ethernet networks, devices use MAC addresses at the data link layer to deliver frames, while IP addresses operate at the network layer to identify devices logically. ARP serves as the bridge between these two layers, allowing devices to translate logical IP addresses into physical hardware addresses, which is essential for successful communication on the same subnet. Without ARP, devices would have no way of determining the MAC address of a device associated with a given IP address, and local network communication would fail.
When a device needs to send data to another device on the same local network, it first checks its ARP table, a temporary database that stores IP-to-MAC address mappings learned over time. If the IP address of the destination device is not present in the table, the device broadcasts an ARP request on the network, asking “Who has this IP address?” The device that owns the IP address responds with an ARP reply containing its MAC address. The sender then stores this mapping in its ARP table for future communication. This process allows devices to dynamically discover the necessary hardware address, ensuring that data is delivered to the correct destination. ARP operates transparently and automatically, which significantly simplifies network management and reduces the potential for configuration errors in dynamic network environments.
ARP is particularly important because it supports efficient communication at the local network level. By learning the MAC addresses associated with IP addresses automatically, devices can maintain accurate mapping tables, enabling seamless frame delivery without manual intervention. ARP also supports functions such as duplicate address detection, helping to prevent IP conflicts within a subnet, and ensures that devices can reliably communicate as the network topology changes or as devices join and leave the network. This dynamic learning capability is a cornerstone of modern Ethernet networking and underpins the operation of most IPv4-based networks.
Other protocols in networking serve different purposes and do not provide the same IP-to-MAC mapping functionality as ARP. DNS, or Domain Name System, translates human-readable hostnames into IP addresses, allowing users to access websites and resources using names instead of numeric addresses. While DNS is essential for name resolution, it does not provide the MAC address required for data link layer communication. DHCP, or Dynamic Host Configuration Protocol, dynamically assigns IP addresses and other configuration parameters to devices, but it does not resolve IP addresses to MAC addresses. ICMP, the Internet Control Message Protocol, is used primarily for network diagnostics, error reporting, and connectivity testing, such as with the ping command, but it does not provide address resolution between IP and MAC addresses.
Because the question specifically asks about learning IP-to-MAC mappings automatically, ARP is the correct solution. It allows devices to dynamically discover the hardware addresses associated with IP addresses, enabling accurate and efficient communication on a local network. By maintaining up-to-date ARP tables and automatically resolving IP addresses to MAC addresses, ARP ensures that devices can reliably transmit data, supports network scalability, and reduces administrative overhead, making it an indispensable protocol for local network operations.
Question 223
Which type of IPv4 address allows one-to-many communication to a specific group of devices?
A) Multicast
B) Unicast
C) Broadcast
D) Anycast
Answer: A) Multicast
Explanation
Multicast addressing is a specialized network communication method that allows a single source to send data to multiple devices that have explicitly joined a specific multicast group. Unlike unicast, which involves one-to-one communication between a sender and a single recipient, multicast enables one-to-many communication without requiring the sender to transmit multiple copies of the same data individually to each recipient. This approach is highly efficient, particularly in scenarios where the same data needs to be delivered simultaneously to a group of interested devices, such as video streaming, live broadcasts, online conferencing, or software updates distributed across multiple hosts in a network. By using multicast, network traffic is minimized, conserving bandwidth and reducing the load on both the source and intermediate network devices.
When a device sends data to a multicast group, only the devices that have joined that group receive the traffic. Devices indicate their interest in a particular multicast group using protocols such as Internet Group Management Protocol (IGMP) for IPv4 or Multicast Listener Discovery (MLD) for IPv6. Network devices, such as routers and switches, use this information to determine which interfaces should forward the multicast traffic, ensuring that only the subscribed devices receive it. This selective forwarding prevents unnecessary data transmission to devices that do not need the information, enhancing overall network efficiency and reducing congestion compared to broadcasting to all devices in a subnet.
Multicast addresses are different from other types of network addresses, each of which serves a distinct purpose. Unicast addresses are used for one-to-one communication, where a single sender transmits data directly to a single recipient. While unicast ensures precise delivery, it is not efficient for delivering the same data to multiple recipients, as it requires multiple transmissions, increasing bandwidth consumption. Broadcast addresses, in contrast, send data to all devices within a subnet. Although broadcast can reach every device, it is not selective, which can lead to unnecessary network traffic and potential congestion, especially in large networks. Anycast addresses are another distinct type, where the same address is assigned to multiple devices, and traffic is routed to the nearest device based on network topology. Anycast is useful for load balancing and improving response times for distributed services, but it does not target a specific group of devices.
The advantage of multicast lies in its ability to target a specific group of devices efficiently. Applications such as live video streaming or online webinars benefit from multicast because the same media stream is delivered simultaneously to all participants without sending multiple copies over the network. Similarly, software updates or configuration messages can be transmitted to a specific set of devices without affecting devices outside the group. This not only optimizes bandwidth usage but also improves overall network performance and scalability.
Because the question specifically asks about sending traffic to a particular group of devices, multicast is the correct addressing method. It enables one-to-many communication while ensuring that only the intended recipients receive the traffic. By providing efficient, selective distribution of data, multicast addressing supports modern network applications that require simultaneous delivery to multiple devices, reduces unnecessary network load, and enhances the performance and scalability of networks, making it a critical tool for group communication in both local and wide-area network environments.
Question 224
Which command displays all routes learned via EIGRP on a router?
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
The show ip route eigrp command is an essential tool for network administrators working with networks that utilize the Enhanced Interior Gateway Routing Protocol (EIGRP). EIGRP is an advanced distance-vector routing protocol that provides rapid convergence, efficient routing, and support for multiple network layer protocols. One of the key capabilities of EIGRP is its ability to dynamically learn routes from neighboring routers and maintain an updated routing table, which allows devices to make intelligent forwarding decisions. The show ip route eigrp command specifically displays all routes that have been learned through EIGRP, providing critical information about destination networks, next-hop IP addresses, and administrative distances. This information is vital for network troubleshooting, verification, and ensuring proper route propagation across the network.
When a router participates in EIGRP, it exchanges routing updates with its EIGRP neighbors. These updates include information about the networks each router can reach, along with metrics such as bandwidth, delay, load, and reliability, which EIGRP uses to calculate the most efficient path to each destination. The routes learned from these updates are stored in the router’s routing table, but only those that are considered the best paths are installed into the main routing table. By using the show ip route eigrp command, administrators can filter the routing table to display only the routes learned via EIGRP, providing a clear view of how EIGRP is influencing the device’s routing decisions. This filtered view is particularly useful in networks where multiple routing protocols, such as OSPF or RIP, might be running simultaneously.
Other commands provide related network information but do not offer the same focus on EIGRP-learned routes. For instance, the show ip route ospf command displays routes learned via OSPF, another dynamic routing protocol, but it does not include any EIGRP-specific routes. Similarly, show ip protocols provides configuration details and timers for routing protocols running on the device, including EIGRP, OSPF, or RIP, but it does not show the actual learned routes or their metrics. While show running-config displays the active configuration of the device, including EIGRP network statements and settings, it does not provide real-time information about dynamically learned routes or the current state of the routing table. Therefore, while these commands are useful for configuration verification and protocol monitoring, they cannot replace show ip route eigrp when the goal is to examine EIGRP-learned routes.
The show ip route eigrp command provides more than just a list of networks; it also shows the next-hop IP addresses, which indicate how traffic is forwarded toward each destination, and the administrative distance, which helps determine route preference when multiple protocols advertise the same network. This information is invaluable for troubleshooting connectivity issues, verifying route propagation, and ensuring that the most efficient paths are being used. By examining the output, administrators can detect problems such as missing routes, misconfigurations, or suboptimal routing decisions, allowing them to correct issues before they affect network performance.
Because the question specifically asks for routes learned through EIGRP, the show ip route eigrp command is the correct choice. It provides a focused, real-time view of all EIGRP-learned routes, including destination networks, next-hop addresses, and administrative distance. This makes it an indispensable tool for maintaining efficient and reliable routing, diagnosing network issues, and ensuring that EIGRP is functioning as intended across the network. By leveraging this command, administrators can achieve better network visibility, optimize routing performance, and maintain a stable and responsive network infrastructure.
Question 225
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
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Link-local addresses are a fundamental aspect of IPv6 networking, providing automatically assigned addresses that allow devices to communicate on the same local link without requiring any manual configuration. Every IPv6-enabled interface is automatically assigned a link-local address, which falls within the FE80::/10 address range. These addresses are essential for local network operations because they enable basic communication between devices on the same subnet, support neighbor discovery, and facilitate certain routing protocol operations. Link-local addresses are not routable beyond the local link, which makes them inherently suited for local communication tasks and ensures that their use does not interfere with global or external network traffic.
One of the most important uses of link-local addresses is in the Neighbor Discovery Protocol (NDP), which is the IPv6 equivalent of ARP in IPv4. NDP relies on link-local addresses to discover other devices on the same link, determine their link-layer addresses, and detect duplicate IP addresses. This process ensures that devices can communicate effectively with their immediate neighbors and prevents address conflicts on the network. Additionally, link-local addresses are used by many routing protocols, such as OSPFv3 and EIGRP for IPv6, to exchange routing information between adjacent routers. By using link-local addresses for these communications, routing updates remain confined to the local link, improving security and simplifying the protocol’s operation.
Link-local addresses differ significantly from other IPv6 address types, each of which serves a specific purpose. Global unicast addresses are routable across the internet and are intended for long-distance communication between devices on different networks. While global addresses allow connectivity across wide areas, they are not automatically assigned to interfaces and cannot be relied upon for immediate local-link operations. Multicast addresses are used to deliver packets to a group of subscribed devices, enabling efficient one-to-many communication for services like video streaming or group notifications. Anycast addresses, on the other hand, are assigned to multiple devices, and packets sent to an anycast address are delivered to the nearest device based on routing metrics. While multicast and anycast have their own advantages, neither provides the automatically assigned, local-link-specific functionality that link-local addresses offer.
The automatic nature of link-local addressing ensures that every IPv6 interface can participate in essential local communication as soon as it is enabled. This eliminates the need for manual configuration of addresses for basic operations, reducing administrative overhead and minimizing configuration errors. Because link-local addresses are always available, devices can reliably perform neighbor discovery, local routing, and network troubleshooting immediately upon activation.
Because the question specifically asks about automatic link-local communication, link-local addresses are the correct choice. They provide a reliable, automatically assigned mechanism for communication confined to the local link, supporting critical network functions such as neighbor discovery and local routing protocol exchanges. By ensuring that every interface has a guaranteed, local-link-specific address, link-local addressing forms the foundation for IPv6 networking, enabling devices to communicate efficiently and securely within a single subnet while maintaining simplicity, reliability, and operational consistency.