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Question 31:
Which command is used to test end-to-end connectivity between two IP hosts?
A) ping
B) traceroute
C) show ip route
D) show interfaces
Answer:
A)
Explanation:
The ping command is one of the most fundamental tools for network troubleshooting and verification. It uses ICMP Echo Request and Echo Reply messages to test the reachability of a host across an IP network. By sending packets to the destination IP address, ping allows administrators to determine whether the target host is responding and measure round-trip latency.
Ping is often the first command used when diagnosing connectivity issues because it provides immediate feedback on network status. If a host does not respond, the administrator can investigate physical connectivity, interface configurations, routing tables, or firewall rules.
While traceroute identifies the path packets take through the network by reporting each hop along the route, ping focuses solely on verifying end-to-end reachability. Show ip route displays routing information, which is useful for understanding path selection but does not actively test connectivity. Show interfaces shows the operational status of interfaces but does not test network reachability.
In CCNA scenarios, mastering ping is critical for troubleshooting network connectivity issues, confirming IP configuration accuracy, and diagnosing problems with routing or firewall policies. Additionally, ping is often combined with extended options for testing specific interfaces or using different ICMP packet sizes.
Question 32:
Which IPv4 address class is intended for very large networks with millions of hosts?
A) Class A
B) Class B
C) Class C
D) Class D
Answer:
A)
Explanation:
Class A IPv4 addresses are designed to accommodate very large networks with millions of hosts. IPv4 addressing is divided into classes, each with a specific range and purpose. Class A addresses occupy the range from 0.0.0.0 to 127.255.255.255, but the usable range for hosts is 1.0.0.0 to 126.255.255.255, because 0.0.0.0 is reserved for default routing and 127.0.0.0/8 is reserved for loopback testing. Class A addresses are characterized by a default subnet mask of 255.0.0.0, which means that the first 8 bits represent the network portion and the remaining 24 bits represent the host portion. This allows for 2^24 minus 2 usable host addresses per network, which amounts to over 16 million hosts per Class A network, making it ideal for extremely large organizations or global enterprises.
The allocation of Class A addresses is controlled and limited due to their vast capacity, and they were historically assigned to large companies, telecommunications providers, or government agencies requiring massive address space. The first bit of a Class A address is always set to 0, which distinguishes it from other address classes. The remaining 7 bits in the first octet define 128 possible Class A networks, though some addresses are reserved for special purposes.
Class B addresses, in comparison, are intended for medium-sized networks, supporting up to 65,534 hosts per network with a default subnet mask of 255.255.0.0. Class C addresses are for smaller networks, supporting up to 254 hosts per network with a default subnet mask of 255.255.255.0. Class D addresses are reserved for multicast communication rather than traditional host addressing and cannot be used to assign IP addresses to individual hosts. Therefore, when an organization requires millions of host addresses within a single network, Class A is the appropriate choice.
Using Class A addresses requires careful planning and management due to the potential for waste of address space if the network does not actually require millions of hosts. Subnetting within Class A networks allows network administrators to divide the large address space into smaller, more manageable subnets, thereby improving network efficiency, reducing broadcast domains, and enhancing security. Subnetting also ensures that unused address space is not wasted and that network segments can be logically separated according to organizational requirements.
In modern networking, with the depletion of IPv4 addresses, Class A addresses are scarce and mostly already assigned. Organizations often rely on private IP addressing, network address translation (NAT), or IPv6 for scalability. However, understanding Class A addressing is fundamental for network engineers, particularly in CCNA-level studies, because it forms the basis for understanding subnetting, routing, and IP address allocation.
In , Class A IPv4 addresses are specifically designed for very large networks with millions of hosts, providing a substantial host capacity per network. They are distinguished by the first bit being 0, a default subnet mask of 255.0.0.0, and the ability to support over 16 million hosts per network. Correct understanding of Class A addressing is critical for planning, subnetting, and managing extremely large-scale networks efficiently. Therefore, the correct option for networks requiring millions of hosts is Class A.
Question 33:
Which technology allows multiple physical links between switches to operate as a single logical link?
A) EtherChannel
B) StackWise
C) VLAN
D) STP
Answer:
A)
Explanation:
EtherChannel aggregates multiple physical Ethernet links into a single logical link to provide increased bandwidth and redundancy between switches or between switches and servers. It allows traffic to be distributed across the member links using hashing algorithms, which take source/destination MAC or IP addresses into account.
If one physical link in an EtherChannel bundle fails, traffic is automatically redistributed across remaining links without disruption, providing resilience. EtherChannel can operate in two modes: PAgP (Cisco proprietary) and LACP (IEEE standard), which negotiate link bundling automatically.
StackWise unifies multiple switches into a single logical device for management purposes but does not aggregate links for bandwidth. VLANs segment traffic logically, and STP prevents Layer 2 loops. EtherChannel is a core CCNA topic, especially for understanding redundancy, load balancing, and configuration best practices in enterprise LANs.
Question 34:
Which command verifies which ports are assigned to which VLAN?
A) show vlan brief
B) show interfaces
C) show ip route
D) show mac address-table
Answer:
A)
Explanation:
The command show vlan brief on a Cisco switch is used to verify VLAN configuration and determine which switch ports are assigned to each VLAN. This command provides a concise overview of all VLANs that are configured on the switch, their VLAN IDs, names, status, and the interfaces associated with them. It is an essential tool for network administrators to validate VLAN assignments, troubleshoot connectivity issues, and ensure proper segmentation of network traffic.
When a switch is configured with multiple VLANs, each VLAN represents a distinct broadcast domain. Properly assigning ports to VLANs is critical to maintain network segmentation, isolate traffic, and enforce security policies. By running show vlan brief, administrators can quickly identify whether each physical port on the switch is assigned to the correct VLAN, whether a VLAN is active or inactive, and whether any ports are unassigned or in an unexpected VLAN. This verification helps prevent misconfigurations that could lead to communication issues, security breaches, or unintended broadcast traffic across VLANs.
The output of show vlan brief typically includes the VLAN ID, VLAN name, status (active or suspended), and a list of ports assigned to each VLAN. For example, an administrator might see VLAN 10 named “Sales” with ports FastEthernet0/1 through 0/5 assigned, and VLAN 20 named “Marketing” with ports FastEthernet0/6 through 0/10 assigned. This clear mapping allows network engineers to validate that devices connected to specific ports are in the correct broadcast domain and can communicate with other devices in the same VLAN while being isolated from other VLANs.
Using this command is also valuable during troubleshooting. For instance, if a device is unable to communicate with other devices in its VLAN, running show vlan brief allows administrators to confirm whether the port is assigned to the intended VLAN or if it has been misconfigured. It also helps detect VLANs that may be administratively shut down or not active, which can be the root cause of connectivity problems. Additionally, the command assists during network expansion or reconfiguration, as administrators can plan port assignments and verify that newly added devices are correctly integrated into the appropriate VLANs.
Other commands listed in the options serve different purposes. show interfaces provides detailed information about interface status, errors, and operational statistics, but does not summarize VLAN assignments. show ip route displays routing table information for Layer 3 IP routing, which is unrelated to Layer 2 VLAN port assignments. show mac address-table shows which MAC addresses are associated with which ports and VLANs but does not provide a concise summary of all configured VLANs and their associated interfaces, making it less practical for a quick VLAN overview.
Question 35:
Which protocol provides automatic IP address assignment to hosts?
A) DHCP
B) ARP
C) ICMP
D) DNS
Answer:
A)
Explanation:
The correct answer is DHCP, which stands for Dynamic Host Configuration Protocol. DHCP is a network management protocol used to automate the process of assigning IP addresses, subnet masks, default gateways, and other network configuration parameters to devices on a TCP/IP network. Without DHCP, network administrators would need to manually assign IP addresses to each device, which can be time-consuming, prone to human error, and difficult to manage in large networks. By automating IP assignment, DHCP ensures that devices can join a network seamlessly and communicate effectively.
When a host connects to a network, it sends a DHCP discovery broadcast to locate available DHCP servers. The DHCP server responds with an offer, including an available IP address and configuration details. The client then requests the offered IP, and the server acknowledges the assignment, completing the lease process. This dynamic allocation allows IP addresses to be reused efficiently, preventing address conflicts and ensuring that limited IP space is utilized optimally. Leases are time-bound, and when they expire, IP addresses can be reassigned to other devices, maintaining a flexible and scalable addressing system.
DHCP also supports additional options such as DNS server addresses, domain names, and NTP servers, allowing hosts to receive complete configuration information automatically. This reduces the administrative overhead and simplifies network management, especially in environments where devices frequently join and leave the network, such as offices, schools, or public Wi-Fi networks. In enterprise networks, DHCP can be integrated with authentication systems like 802.1X to ensure that only authorized devices receive network configuration.
Other protocols listed serve different purposes. ARP (Address Resolution Protocol) maps IP addresses to MAC addresses to enable local delivery of packets but does not assign IP addresses. ICMP (Internet Control Message Protocol) is used for error reporting, diagnostics, and network testing, such as the ping command, but it does not configure host addressing. DNS (Domain Name System) translates human-readable domain names to IP addresses, facilitating hostname resolution rather than providing automatic network configuration.
DHCP is essential for maintaining consistency and avoiding manual misconfigurations in networks of all sizes. It provides central control over IP address allocation, supports both static and dynamic leases, and can be configured with failover and redundancy to ensure high availability. Network administrators can reserve specific IP addresses for critical devices, ensuring predictable addressing, while still allowing dynamic assignment for general hosts.
Question 36:
Which command displays the active routes on a router?
A) show ip route
B) show running-config
C) show interfaces
D) show mac address-table
Answer:
A)
Explanation:
The show ip route command provides a detailed view of a router’s active routing table, including connected networks, static routes, and dynamically learned routes via routing protocols. The output includes route sources, next-hop addresses, administrative distance, and metrics, which are vital for troubleshooting path selection.
Show running-config displays the router’s configuration but does not provide routing status. Show interfaces provides interface operational data, while show mac address-table is used on switches to verify Layer 2 forwarding information.
CCNA candidates must interpret routing tables, understand route selection, and identify missing or incorrect routes to troubleshoot connectivity issues. Mastery of this command is essential for real-world network administration.
Question 37:
Which VLAN type is used to forward traffic between multiple switches?
A) Trunk VLAN
B) Access VLAN
C) Management VLAN
D) Voice VLAN
Answer:
A)
Explanation:
The correct answer is Trunk VLAN because it is specifically used to carry traffic from multiple VLANs across a single physical link between switches. In a network, VLANs (Virtual Local Area Networks) are used to segment broadcast domains, improve security, and organize devices logically, regardless of physical location. Access VLANs, on the other hand, are assigned to individual switch ports and carry traffic for a single VLAN only. Management VLAN is reserved for network management traffic such as SNMP or remote administrative access, while Voice VLAN is used to prioritize VoIP traffic.
A trunk link allows multiple VLANs to traverse a single connection between two switches, routers, or other network devices. This is achieved using tagging protocols such as IEEE 802.1Q, which inserts VLAN identification into Ethernet frames. Each frame transmitted over the trunk link carries a VLAN tag, allowing the receiving switch to determine which VLAN the traffic belongs to. This tagging mechanism ensures that multiple VLANs can coexist on the same physical link without interference and maintain logical separation. Trunking is essential in larger networks where multiple VLANs need to span across several switches, enabling centralized management and consistent VLAN membership throughout the network.
When configuring trunk ports, network administrators designate which VLANs are allowed on the trunk. By default, all VLANs may be permitted, but administrators often restrict the allowed VLANs to improve security and reduce unnecessary traffic. Trunk links also support features like VLAN pruning, which prevents broadcast and multicast traffic from unused VLANs from traversing the link, optimizing bandwidth usage. Protocols like Dynamic Trunking Protocol (DTP) can automatically negotiate trunking between switches, simplifying configuration in certain environments, though static trunk configuration is often preferred for stability.
Access VLANs, in contrast, are intended for end devices such as computers or printers. Each access port belongs to a single VLAN and does not tag outgoing traffic. Frames received on an access port are assumed to belong to the port’s VLAN. Management VLANs provide a dedicated channel for administrative communication to manage devices, often segregated from user traffic to enhance security. Voice VLANs are configured to prioritize IP phone traffic and ensure quality of service (QoS) for voice communications.
Trunk VLANs are critical for enterprise networks that require multiple VLANs to extend across different switches and maintain the same network segmentation throughout the organization. Without trunking, VLANs would be confined to a single switch, limiting scalability and requiring complex configurations with multiple physical connections to carry multiple VLANs. Trunking simplifies network design, reduces cabling complexity, and allows VLANs to span multiple switches efficiently.
Question 38:
Which protocol ensures loop-free topology in Layer 2 networks?
A) STP
B) OSPF
C) EIGRP
D) RIP
Answer:
A)
Explanation:
The correct answer is STP, which stands for Spanning Tree Protocol. STP is a Layer 2 network protocol that ensures a loop-free topology in Ethernet networks by preventing switching loops caused by redundant links. Redundant links are often implemented intentionally to provide fault tolerance and improve network reliability, but without STP, multiple active paths can create loops, leading to broadcast storms, multiple frame copies, MAC table instability, and degraded network performance. STP automatically detects loops and blocks redundant paths while keeping one active path to ensure seamless connectivity.
STP operates by electing a root bridge, which acts as the reference point for the network topology. Each switch calculates the shortest path to the root bridge based on path cost, which is determined by the bandwidth of links. Non-optimal paths are placed into a blocking state to prevent loops. Ports are assigned roles such as root port, designated port, or alternate port, and their states include blocking, listening, learning, and forwarding. The algorithm continuously monitors the network, recalculating paths if topology changes occur due to link failures, addition of new switches, or configuration updates. This dynamic process allows STP to maintain a stable and loop-free Layer 2 network while accommodating changes without manual intervention.
Other protocols listed operate at different layers or serve different purposes. OSPF is a Layer 3 link-state routing protocol that calculates shortest paths for IP routing using the Dijkstra algorithm. While OSPF ensures efficient Layer 3 routing, it does not prevent Layer 2 loops. EIGRP is a distance-vector routing protocol used for Layer 3 path selection and convergence within an autonomous system. RIP is also a Layer 3 distance-vector protocol that uses hop count to determine routing paths but does not address Layer 2 topology issues. Neither OSPF, EIGRP, nor RIP manage redundant Layer 2 links or prevent broadcast loops.
STP also provides features for enhanced network design and stability. Rapid Spanning Tree Protocol (RSTP) is an evolution of STP that offers faster convergence times, reducing network downtime when topology changes occur. Multiple STP instances can run simultaneously in environments with VLANs using Multiple Spanning Tree Protocol (MSTP), providing loop prevention across segmented Layer 2 networks. Administrators can also configure port priorities and path costs to influence the selection of root and designated ports, optimizing traffic flow and redundancy.
In practice, implementing STP is essential in enterprise networks where multiple switches and redundant links exist. Without STP, loops can cause network-wide outages, packet loss, and severe performance degradation. By deploying STP, administrators can achieve redundancy, prevent network loops, and ensure a reliable, stable Layer 2 network infrastructure.
Question 39:
Which addressing type allows one-to-many communication?
A) Multicast
B) Unicast
C) Broadcast
D) Loopback
Answer:
A)
Explanation:
The correct answer is multicast because it is the addressing type specifically designed for one-to-many communication in IP networks. Unlike unicast, where data is sent from one source to a single destination, multicast allows a sender to deliver a single stream of data to multiple interested receivers efficiently without sending separate copies to each recipient. This approach significantly reduces bandwidth usage and optimizes network performance, especially in scenarios such as video conferencing, live streaming, IPTV, and real-time stock updates.
Multicast uses reserved IP address ranges to identify groups of devices that want to receive the traffic. In IPv4, these addresses fall within the 224.0.0.0 to 239.255.255.255 range, known as the Class D address space. Hosts that want to receive a multicast transmission join the multicast group by signaling their interest using the Internet Group Management Protocol (IGMP). Routers on the network use multicast routing protocols, such as Protocol Independent Multicast (PIM), to forward multicast traffic only to segments of the network where group members exist. This selective delivery prevents unnecessary flooding of traffic to devices that do not need it, maintaining overall network efficiency.
Unicast, on the other hand, is a one-to-one communication method where data travels from a single source to a single destination. While it is suitable for typical point-to-point communication, using unicast to send the same data to multiple recipients would require multiple copies of the same data, consuming excessive bandwidth and increasing network load. Broadcast is a one-to-all addressing type where data is sent to all hosts on a subnet. Although it can deliver information to multiple devices, broadcast is limited to the local subnet and generates unnecessary traffic to hosts that do not need the information, which is inefficient for large-scale or multi-subnet networks. Loopback is not a communication method for external devices; it is an internal testing address used by a device to verify its own TCP/IP stack.
Multicast addressing is critical in modern network environments, especially where bandwidth optimization and scalability are important. Examples include delivering software updates to multiple servers simultaneously, streaming live video to numerous subscribers, or sending real-time alerts to a group of monitoring systems. Multicast ensures that only devices that have explicitly joined the multicast group receive the data, which reduces network congestion and improves the performance of critical applications.
Question 40:
Which routing protocol uses the Dijkstra algorithm for path calculation?
A) OSPF
B) RIP
C) EIGRP
D) BGP
Answer:
A)
Explanation:
The correct answer is OSPF, which stands for Open Shortest Path First. OSPF is a link-state routing protocol that uses the Dijkstra algorithm, also known as the Shortest Path First (SPF) algorithm, to calculate the most efficient path between routers within an autonomous system. Unlike distance-vector protocols such as RIP, which rely on hop count and periodic updates, OSPF maintains a complete map of the network topology through the exchange of link-state advertisements (LSAs) between routers. This detailed knowledge allows OSPF to compute optimal routes based on cost metrics assigned to each link, resulting in faster convergence and more efficient routing decisions.
When OSPF routers start or detect a topology change, they flood LSAs to all OSPF neighbors. Each router then builds a Link-State Database (LSDB) representing the entire network topology. The Dijkstra algorithm is applied to the LSDB to calculate the shortest path tree for each router, with itself as the root. The resulting SPF tree determines the best path to every destination in the network. This approach ensures loop-free and efficient routing by considering all available paths and their associated costs rather than simply counting hops.
RIP, by contrast, is a distance-vector protocol that uses hop count as its metric and does not maintain a complete map of the network. It periodically sends its routing table to neighbors and converges more slowly, making it less suitable for large or complex networks. EIGRP is a hybrid protocol that uses the Diffusing Update Algorithm (DUAL) for path calculation and is considered faster than RIP, but it does not use the Dijkstra algorithm. BGP is an exterior gateway protocol used between autonomous systems and uses path vector mechanisms and policy-based metrics rather than link-state calculations.
OSPF supports hierarchical network design through areas, which reduces routing overhead and improves scalability. The backbone area (Area 0) connects all other areas, ensuring optimal routing and loop prevention. By using the Dijkstra algorithm, OSPF can efficiently handle multiple paths and changes in topology, recalculating routes quickly when a link fails or when a new router is added. This makes OSPF highly reliable and suitable for large enterprise networks where fast convergence and predictable routing are critical.
The Dijkstra algorithm itself is a mathematical method that computes the shortest path between nodes in a weighted graph, making it ideal for OSPF’s link-state routing approach. By assigning costs to links based on bandwidth, administrators can influence routing decisions and prioritize high-speed connections. This flexibility and accuracy in route calculation is one of OSPF’s primary advantages over simpler protocols like RIP.
Question 41:
Which protocol resolves IP addresses to MAC addresses in IPv4 networks?
A) ARP
B) DHCP
C) ICMP
D) DNS
Answer:
A)
Explanation:
The correct answer is ARP, which stands for Address Resolution Protocol. ARP is a fundamental protocol used in IPv4 networks to map a device’s IP address to its corresponding MAC address, enabling proper delivery of packets on a local area network. Every device on an Ethernet network has a unique MAC address assigned to its network interface card. While IP addresses are used for logical addressing and routing across networks, MAC addresses are used for actual frame delivery at the data link layer. ARP bridges the gap between these two layers, ensuring that packets sent to a specific IP address reach the correct physical device.
When a host wants to communicate with another device on the same subnet, it first checks its ARP cache to see if the MAC address corresponding to the target IP address is already stored. If it is not present, the host broadcasts an ARP request on the local network, asking, “Who has this IP address?” The device with the matching IP responds with an ARP reply, providing its MAC address. The sender then caches this mapping for future communication to reduce network broadcast traffic. This process is essential for efficient Ethernet communication and ensures that IP-layer packets can be encapsulated into Ethernet frames and delivered correctly.
Other protocols listed serve different purposes. DHCP (Dynamic Host Configuration Protocol) assigns IP addresses to devices automatically but does not resolve IP addresses to MAC addresses. ICMP (Internet Control Message Protocol) is used for error reporting and diagnostics, such as the ping command, but it does not perform address resolution. DNS (Domain Name System) translates human-readable domain names to IP addresses for routing across networks, but it does not handle MAC addresses or local delivery within a subnet.
ARP operates only within a local broadcast domain, meaning it cannot resolve IP addresses across different networks without routing. Routers maintain ARP tables for each interface, allowing communication between different subnets using IP routing. Efficient ARP management is crucial in large networks because excessive ARP broadcasts can lead to broadcast storms, reducing network performance. Modern networks implement techniques like ARP caching, static ARP entries, and proxy ARP to optimize performance and security.
In , ARP is the protocol responsible for resolving IPv4 addresses to MAC addresses on local networks. It allows devices to communicate at the data link layer by mapping logical IP addresses to physical hardware addresses. Without ARP, devices would not be able to deliver packets to the correct Ethernet interface, making it a fundamental component of IPv4 networking. This makes ARP the correct and necessary choice for IP-to-MAC address resolution.
Question 42:
Which IPv4 address range is private for internal networks?
A)168.0.0 – 192.168.255.255
B) 8.8.8.0 – 8.8.8.255
C) 172.16.0.0 – 172.31.255.255
D) 224.0.0.0 – 239.255.255.255
Answer:
A) and C)
Explanation:
The correct answers are 192.168.0.0 – 192.168.255.255 and 172.16.0.0 – 172.31.255.255 because these address ranges are designated as private IPv4 addresses for internal use according to RFC 1918. Private addresses are not routable on the public internet, which makes them ideal for internal networks such as LANs, branch offices, and corporate environments. These addresses allow organizations to assign IPs internally without consuming globally unique addresses, conserving public IP resources.
The 192.168.0.0 – 192.168.255.255 range is commonly used in small office and home networks. This range is a Class C private network and provides 256 contiguous subnets, each with 254 usable host addresses. The popularity of this range stems from the simplicity of configuring home routers and small-scale networks, as devices such as PCs, printers, and IoT devices can be easily assigned addresses within this subnet. Network Address Translation (NAT) is typically used to allow devices in this private range to access the internet by translating private addresses to a single public IP.
The 172.16.0.0 – 172.31.255.255 range is part of the Class B private address space. It provides a larger address range suitable for medium to large organizations. This range includes 16 contiguous Class B networks, each supporting 65,534 hosts. Enterprises often use this space for internal VLANs, departmental segmentation, and hierarchical IP addressing schemes. By utilizing the 172.16.0.0 – 172.31.255.255 range, administrators can implement subnetting strategies to efficiently manage large numbers of devices while maintaining internal network isolation from the public internet.
These private ranges are protected from direct exposure to the internet, which enhances network security. Using NAT or PAT, multiple internal hosts can share a single public IP for external communications while maintaining unique private addresses internally. This setup helps prevent unauthorized access to internal resources while allowing controlled internet connectivity.
Other options do not represent private addresses. The 8.8.8.0 – 8.8.8.255 range belongs to Google’s public DNS servers and is globally routable. The 224.0.0.0 – 239.255.255.255 range is reserved for multicast communication, which allows sending data to multiple hosts using a single address but is not used for private internal networks.
In ,, the 192.168.0.0 – 192.168.255.255 and 172.16.0.0 – 172.31.255.255 ranges are designated for private internal use. They are non-routable on the public internet, allow organizations to deploy devices and subnets efficiently, and help conserve public IP addresses. Proper use of these ranges, along with NAT, ensures secure and manageable network design for small to large-scale internal networks.
Question 43:
Which routing protocol is classless and supports VLSM?
A) RIPv2
B) RIP v1
C) IGRP
D) BGP
Answer:
A)
Explanation:
The correct answer is RIPv2 because it is a classless routing protocol that supports Variable Length Subnet Masking (VLSM). In networking, classless protocols allow the use of subnet masks of varying lengths, which provides flexibility in IP address allocation and efficient use of IP space. RIPv2 is an enhancement of the original RIP version 1, which was classful and did not include subnet mask information in its routing updates. As a result, RIPv2 can carry subnet information with its routing updates, allowing routers to handle networks with different subnet masks on different interfaces effectively.
RIPv2 operates using distance-vector routing principles, where each router periodically shares its routing table with neighboring routers. The distance metric is based on hop count, with a maximum of 15 hops allowed. Any route beyond 15 hops is considered unreachable, which limits the scalability of RIPv2 but makes it simple and suitable for smaller networks. Unlike RIP v1, which assumes the default classful boundaries of networks, RIPv2 can work with subnets of varying sizes, making it compatible with modern network designs that use VLSM to conserve IP address space.
Support for VLSM allows network administrators to divide IP address ranges into subnets of different sizes according to actual host requirements. For example, a subnet with only a few hosts does not need a large address space, while a subnet serving many devices can be allocated more addresses. RIPv2’s ability to handle these varying subnet sizes prevents the wastage of IP addresses and improves network efficiency. Additionally, RIPv2 supports multicast updates, sending routing information to the multicast address 224.0.0.9 instead of broadcasting to all devices. This reduces unnecessary traffic and enhances network performance.
Other protocols listed do not fully meet these requirements. RIP v1 is classful, does not include subnet mask information, and cannot support VLSM. IGRP is also classful and designed primarily for large networks under older Cisco architectures; it does not support VLSM either. BGP, on the other hand, is an exterior gateway protocol used for routing between autonomous systems on the Internet. While BGP is classless and supports CIDR, it is not typically used for internal routing within a LAN or enterprise environment and operates under very different principles compared to RIP.
In practice, RIPv2 is widely used in smaller networks or in scenarios where simplicity is prioritized over scalability. Its support for VLSM allows administrators to implement hierarchical IP addressing efficiently, optimize network address allocation, and reduce waste. Despite limitations in hop count and convergence speed, RIPv2 remains relevant for teaching routing concepts, lab environments, and smaller production networks where routing complexity is low.
In , RIPv2 is the correct choice because it is a classless routing protocol that supports VLSM, allows subnet information to be transmitted in routing updates, and provides flexibility in IP address management. Its enhancements over RIP v1 make it suitable for modern network designs, enabling efficient use of IP address space while maintaining simplicity in configuration and operation.
Question 44:
Which command displays interface IP addresses and status?
A) show ip interface brief
B) show running-config
C) show vlan brief
D) show mac address-table
Answer:
A)
Explanation:
The correct answer is show ip interface brief because this command provides a concise overview of all interfaces on a Cisco device, including their IP addresses, interface status, and protocol state. It is widely used by network administrators to quickly verify configuration and operational conditions without reviewing the detailed running configuration. The output shows the interface name, IP address assigned, whether the interface is administratively up or down, and whether the protocol is operationally up or down. This information helps in determining whether interfaces are configured correctly and are actively participating in network communication.
The show ip interface brief command is particularly useful for troubleshooting connectivity issues. Administrators can quickly identify interfaces that are administratively shut down or interfaces where the protocol is down due to misconfigurations, cabling problems, or physical issues. The command allows for immediate verification of interface IP addressing, which is critical for ensuring proper routing and communication across the network. In networks with multiple VLANs or subnets, this command helps confirm that each interface has been assigned the correct IP address and is functioning as expected.
Other commands listed do not provide the same level of quick operational insight. Show running-config displays the full current configuration of a device, which includes interface settings, routing protocols, and VLAN configurations. While comprehensive, it is much more detailed and requires interpretation to identify interface status and IP information. Show vlan brief provides a summary of VLANs and their associated ports but does not include IP addresses or protocol status for interfaces. Show mac address-table lists MAC addresses learned on each interface, which helps track data forwarding and connectivity at Layer 2, but it does not display IP addresses or whether an interface is operational at Layer 3.
Using show ip interface brief is also efficient for network documentation and audit purposes. Administrators can quickly generate a snapshot of all interfaces and their statuses, which is essential for maintaining accurate network records, verifying configuration changes, and monitoring network health. It provides a practical, real-time view of device connectivity without navigating through extensive configuration details, making it an indispensable tool for both routine operations and troubleshooting.
In , show ip interface brief is the preferred command for displaying interface IP addresses and operational status. It combines ease of use, clarity, and comprehensiveness in a single output, enabling network engineers to quickly verify connectivity, identify misconfigured or down interfaces, and ensure proper IP assignment. This command is essential for efficient network management, proactive troubleshooting, and maintaining operational stability across Cisco network devices.
Question 45:
Which command displays detailed STP information on a Cisco switch?
A) show spanning-tree detail
B) show ip route
C) show vlan brief
D) show mac address-table
Answer:
A)
Explanation:
The correct answer is show spanning-tree detail because this command provides comprehensive information about the Spanning Tree Protocol configuration and status on a Cisco switch. Spanning Tree Protocol operates at Layer 2 and is designed to prevent loops in Ethernet networks, especially when multiple redundant paths exist between switches. Loops can cause broadcast storms, multiple frame copies, and instability in the MAC address table, so STP is critical for maintaining a stable network topology. By using the show spanning-tree detail command, administrators can view detailed information about STP operation on a per-VLAN basis, including root bridge identification, bridge priority, path costs, and the roles and states of all ports participating in STP.
This command displays each port’s state, such as blocking, listening, learning, or forwarding, and indicates whether the port is a root port, designated port, or alternate port. It also provides timing information such as hello time, forward delay, and maximum age, which are important for understanding how quickly the network converges after a topology change. The detailed output allows administrators to verify that the correct switch is acting as the root bridge and that redundant links are properly managed. This insight is essential for troubleshooting STP issues such as unexpected port blocking, suboptimal traffic paths, or network loops.
Other commands listed do not provide STP-specific information. The show ip route command displays the Layer 3 routing table, which is useful for routing and IP connectivity troubleshooting but does not give any Layer 2 loop prevention information. The show vlan brief command lists VLANs and the ports assigned to them but does not provide port roles, states, or path costs related to STP. The show mac address-table command displays the MAC addresses learned by the switch and the corresponding ports, which can help track traffic flow but offers no information about STP topology or port states.
Using show spanning-tree detail is particularly valuable in networks with multiple switches and complex VLAN configurations. It enables administrators to verify STP convergence after adding or removing links, confirm correct root bridge election, and identify any ports that may be in a blocking state unexpectedly. This command also helps in planning network expansions by showing the path costs and priority values for each port, which influence how STP selects the best path. Proper understanding and monitoring of STP through this command prevent network downtime and performance issues caused by loops or misconfigurations.
Show spanning-tree detail is the most effective command for examining STP on Cisco switches. It provides complete visibility into VLAN-specific STP configurations, port roles and states, root bridge information, and timing parameters. Administrators can use this information to maintain a loop-free, stable Layer 2 network, troubleshoot STP-related issues efficiently, and ensure optimal network performance.