200-301 Cisco Certified Network Associate (CCNA) Exam Dumps and Practice Test Questions Set 6 Q101-120

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Question 101: 

Which protocol is used to prevent unauthorized ARP replies on a switch?

A) DHCP Snooping
B) Dynamic ARP Inspection (DAI)
C) Port Security
D) STP

Answer: B

Explanation: 

Dynamic ARP Inspection (DAI) validates ARP packets on untrusted ports, preventing ARP spoofing attacks by allowing only valid ARP responses.

Dynamic ARP Inspection (DAI) is a security feature implemented on network switches to prevent unauthorized or malicious ARP replies. ARP, or Address Resolution Protocol, is essential for mapping IP addresses to MAC addresses within a local network. However, ARP is inherently vulnerable because it does not include a mechanism for authentication, making it susceptible to attacks such as ARP spoofing or ARP poisoning. In such attacks, a malicious device can send forged ARP messages to associate its MAC address with the IP address of another host, allowing it to intercept, modify, or disrupt network traffiC)

Dynamic ARP Inspection mitigates this risk by inspecting all ARP packets received on untrusted ports of a switch. The switch checks the ARP packet against a trusted database, often built using DHCP Snooping, to verify that the source MAC address and IP address match a legitimate entry. Only ARP packets that are validated are allowed to pass through the switch, while any packets that do not match the trusted database are droppeD) This ensures that only valid ARP responses are propagated on the network, effectively preventing ARP spoofing attacks and protecting the integrity of communications within the local network.

Looking at the other options, DHCP Snooping is a complementary security feature that filters untrusted DHCP messages and builds a trusted binding table of IP-to-MAC addresses. While DHCP Snooping provides the database DAI uses for validation, it does not directly inspect ARP packets. Port Security restricts access to a switch port by limiting the number of MAC addresses allowed, preventing unauthorized devices from connecting but not validating ARP messages. Spanning Tree Protocol (STP) is used to prevent network loops in Ethernet networks and does not provide any mechanism to secure ARP traffiC)

Therefore, while DHCP Snooping, Port Security, and STP address different aspects of network security and stability, Dynamic ARP Inspection is specifically designed to validate ARP packets and prevent unauthorized or malicious ARP replies, making it the correct choice for defending against ARP-based attacks.

Question 102: 

A switch is configured with multiple VLANs. Which command shows which ports are assigned to which VLAN?

A) show interfaces status
B) show mac-address-table
C) show vlan brief
D) show ip interface brief

Answer: C

Explanation: 

show vlan brief displays all VLANs, their status, and the ports assigned to each VLAN, helping verify VLAN configurations.

In a network where a switch is configured with multiple VLANs, it is important to know which ports are assigned to which VLANs for proper management and troubleshooting. VLANs, or Virtual Local Area Networks, allow network administrators to segment a physical network into multiple logical networks, improving performance, security, and organization. To verify VLAN configurations, Cisco switches provide several commands, each with a distinct purpose.

The command show vlan brief is specifically designed to display a concise summary of all VLANs configured on a switch. It shows the VLAN identification number (VLAN ID), the VLAN name, its operational status, and, importantly, the ports assigned to each VLAN. This makes it an essential tool for administrators to quickly verify how VLANs are mapped to physical interfaces and ensure devices are correctly segmented according to the network design. By running this command, you can identify active VLANs, detect unused ports, and troubleshoot connectivity issues related to VLAN misconfigurations.

Other commands provide different types of information. show interfaces status lists all interfaces on the switch along with their operational status, speed, and duplex settings, but it does not provide detailed information about VLAN assignments. show mac-address-table displays the MAC addresses learned by the switch and the corresponding ports and VLANs. While this can give some insight into which devices are communicating on a particular VLAN, it does not provide a complete overview of VLAN assignments to all ports. show ip interface brief is used to quickly check IP address configuration and the status of Layer 3 interfaces on a switch or router. It is useful for verifying IP connectivity but does not show VLAN membership.

Therefore, among these options, show vlan brief is the most appropriate command to determine which switch ports belong to which VLANs. It provides a clear and organized summary of VLAN assignments, helping administrators manage network segmentation, verify configurations, and troubleshoot VLAN-related issues efficiently. This command is central to VLAN management in multi-VLAN switch environments.

Question 103: 

Which routing protocol uses a link-state algorithm and supports hierarchical network design with areas?

A) RIP
B) OSPF
C) EIGRP
D) BGP

Answer: B

Explanation: 

OSPF is a link-state protocol that supports areas to reduce routing table size and improve scalability, while RIP and EIGRP are distance-vector protocols.

Routing protocols are essential for enabling routers to exchange information about network topology and determine the best paths for forwarding traffiC) Among the available routing protocols, each has different characteristics, algorithms, and scalability features suited to various network designs.

OSPF, or Open Shortest Path First, is a widely used link-state routing protocol. Unlike distance-vector protocols, which rely on periodic updates and knowledge of their neighbors’ routing tables, link-state protocols like OSPF maintain a complete map of the network topology. Each OSPF router independently calculates the shortest path to all networks using Dijkstra’s algorithm. This approach allows for faster convergence and more efficient routing decisions, especially in large and complex networks. A key feature of OSPF is its support for hierarchical network design through the use of areas. By dividing the network into areas, OSPF reduces the size of routing tables and limits the scope of route recalculations, improving scalability and performance. Area 0, or the backbone area, connects all other areas and ensures proper inter-area communication.

RIP, or Routing Information Protocol, is a distance-vector protocol that uses hop count as its metric and periodically shares its routing table with neighbors. While simple to configure, RIP does not scale well in large networks and lacks support for hierarchical designs or areas. EIGRP, or Enhanced Interior Gateway Routing Protocol, is a Cisco proprietary distance-vector protocol that incorporates features of link-state protocols for faster convergence, but it does not inherently use a hierarchical area structure. BGP, or Border Gateway Protocol, is an exterior gateway protocol designed for routing between autonomous systems on the internet. BGP is path-vector based and operates at a much higher level, focusing on policy-based routing rather than internal network optimization.

In summary, OSPF is the protocol that uses a link-state algorithm and supports hierarchical network design through areas. It offers faster convergence, scalability, and efficient management of large networks, making it a preferred choice for enterprise and large-scale network deployments, whereas RIP, EIGRP, and BGP serve different purposes and do not provide the same area-based hierarchical structure.

Question 104: 

Which IPv4 address is considered private and cannot be routed on the internet?

A) 192.168.1.1
B) 8.8.8.8
C) 172.16.5.5
D) Both A and C

Answer: D

Explanation: 

IPv4 private addresses include 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16. They are not routable on the public internet.

IPv4 addresses are divided into public and private ranges to organize and manage IP space efficiently. Private addresses are reserved for use within local networks and cannot be routed on the public internet. This ensures that internal network devices can communicate securely without conflicting with globally unique public IP addresses.

The address 192.168.1.1 falls within the 192.168.0.0/16 range, which is designated as a private IPv4 address block. This range is commonly used in home and small office networks, and routers often assign addresses in this range via DHCP to internal devices. Because 192.168.1.1 is private, it cannot be accessed directly from the internet; instead, network address translation (NAT) is used to allow devices with private IP addresses to communicate externally.

Similarly, the address 172.16.5.5 belongs to the 172.16.0.0/12 private range, which includes addresses from 172.16.0.0 to 172.31.255.255. This block is often used in larger corporate or enterprise networks, providing more address space for internal hosts compared to the 192.168.0.0/16 block. Like 192.168.1.1, 172.16.5.5 is not routable on the public internet and requires NAT to interact with external networks.

In contrast, the address 8.8.8.8 is a public IP address, specifically one of Google’s public DNS servers. It is routable on the internet and can be accessed globally. Public IP addresses like this are unique and must be assigned by an Internet Service Provider (ISP) to avoid conflicts.

Considering these facts, both 192.168.1.1 and 172.16.5.5 are private IPv4 addresses that cannot be routed on the internet. They are intended solely for internal network use and rely on NAT or other mechanisms to connect to public networks. The private address ranges, including 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16, are fundamental for network design, allowing organizations to implement scalable and secure local networks without consuming scarce public IPv4 space.

The correct answer is both A and C)

Question 105: 

Which command displays all active VLAN trunks on a Cisco switch?

A) show vlan brief
B) show interfaces trunk
C) show spanning-tree
D) show running-config

Answer: B

Explanation: 

show interfaces trunk provides trunk status, allowed VLANs, native VLAN, and encapsulation for all trunk interfaces.

In a Cisco switch environment, VLAN trunks are critical for carrying traffic from multiple VLANs across a single physical link between switches or between a switch and a router. Trunk links allow VLAN segregation to extend beyond a single switch, enabling devices in different VLANs across the network to communicate through routing or layer 3 devices. To manage and troubleshoot VLAN trunks effectively, Cisco provides several commands, each offering different types of information about the switch and its interfaces.

The command show interfaces trunk is specifically designed to display detailed information about all active trunk links on a switch. It shows which interfaces are operating as trunks, the trunking encapsulation type in use (such as IEEE 802.1Q or ISL), the native VLAN for each trunk, and the list of VLANs allowed on the trunk. This command is essential for network administrators to verify that trunking is configured correctly, to troubleshoot VLAN connectivity issues, and to ensure that only the desired VLANs are passing through a trunk. By using show interfaces trunk, administrators can quickly identify misconfigurations or mismatches that could cause communication problems between switches.

Other commands serve different purposes. show vlan brief provides a summary of all VLANs configured on a switch, their status, and the ports assigned to each VLAN. While useful for verifying VLAN assignments, it does not indicate which interfaces are functioning as trunks. show spanning-tree displays the spanning-tree protocol status and topology information, helping prevent network loops, but it does not provide a summary of trunk interfaces or allowed VLANs. show running-config shows the current configuration of the switch, including trunk configuration, VLAN assignments, and interface settings, but this requires parsing through the configuration manually to identify trunk links, which is less efficient than the dedicated trunk display commanD)

Therefore, show interfaces trunk is the correct command to use when the goal is to view all active VLAN trunks on a Cisco switch. It provides a clear and organized summary of trunk status, encapsulation, native VLANs, and permitted VLANs, making it indispensable for trunk verification and network troubleshooting.

Question 106: 

Which type of ACL can filter traffic based on source IP, destination IP, protocol type, and port number?

A) Standard ACL
B) Extended ACL
C) Named ACL
D) Reflexive ACL

Answer: B

Explanation:

Extended ACLs provide granular filtering, including source/destination IP, protocol (TCP/UDP/ICMP), and port numbers, unlike standard ACLs that filter only by source IP.

Access Control Lists (ACLs) are essential tools in network security, used to control and filter traffic passing through routers or switches. They allow network administrators to define rules that permit or deny specific types of traffic based on criteria such as IP addresses, protocols, or ports. Understanding the differences between ACL types is crucial for implementing effective network security policies.

Extended ACLs are the most granular type of ACL and can filter traffic based on multiple parameters. They allow administrators to specify not only the source IP address but also the destination IP address, the protocol type (such as TCP, UDP, or ICMP), and specific port numbers. This level of control enables precise traffic filtering, such as allowing HTTP traffic to a specific server while blocking all other types of traffic from the same source. Because of their flexibility, extended ACLs are commonly used in scenarios where security policies require fine-grained control over network communications.

Standard ACLs, on the other hand, are simpler and filter traffic only by source IP address. While they are easier to configure, they lack the ability to differentiate between different types of traffic or specify destination addresses and ports. This makes standard ACLs suitable for basic traffic filtering but insufficient when more precise control is needeD)

Named ACLs are a variation of both standard and extended ACLs that allow administrators to assign descriptive names to ACLs rather than relying on numerical identifiers. This improves readability and management, especially in large networks, but the filtering capabilities depend on whether the named ACL is configured as standard or extendeD)

Reflexive ACLs are used for more advanced scenarios, providing temporary, dynamic filtering of traffiC) They allow return traffic for sessions initiated from within the network, making them useful for controlling outbound sessions while still permitting the corresponding inbound responses.

In summary, extended ACLs are the type of ACL that can filter traffic based on source and destination IP addresses, protocol type, and port number, providing the highest level of granularity and control among the options. Standard, named, and reflexive ACLs either offer simpler filtering or specialized functionalities.

The correct answer is extended ACL.

Question 107: 

Which command verifies the OSPF process ID and router ID on a Cisco router?

A) show ip route ospf
B) show ip ospf
C) show ip interface brief
D) show running-config

Answer: B

Explanation: 

show ip ospf displays OSPF process IDs, router IDs, area information, and general OSPF statistics.

Open Shortest Path First (OSPF) is a widely used link-state routing protocol that allows routers to exchange topology information within an autonomous system. For network administrators, verifying the OSPF configuration and understanding the state of OSPF processes on a router is critical for ensuring proper routing and troubleshooting network issues. Cisco routers provide several commands for checking OSPF, each serving different purposes.

The command show ip ospf is used specifically to verify OSPF information on a router. When executed, it displays key details such as the OSPF process ID, which identifies a particular OSPF instance on the router, and the router ID, which uniquely identifies the router within the OSPF network. It also provides information about OSPF areas, including area IDs, interface participation in OSPF areas, and general OSPF statistics like the number of neighbors, route calculations, and SPF (Shortest Path First) algorithm operations. This command is essential for administrators to confirm that OSPF is running correctly and that the router is properly participating in its configured areas.

Other commands provide different types of information. show ip route ospf displays the OSPF-learned routes in the router’s IP routing table but does not provide details about the OSPF process ID or router ID) It is useful for checking which networks OSPF has learned and for verifying route propagation, but it does not provide a complete view of the OSPF process itself. show ip interface brief lists all interfaces on the router along with their IP addresses and status, which helps verify connectivity but does not show OSPF-specific information. show running-config displays the router’s current configuration, including OSPF statements, but it requires manual inspection to determine the process ID and router ID, making it less convenient for quick verification.

Therefore, show ip ospf is the appropriate command to verify the OSPF process ID and router ID, as it provides comprehensive information about OSPF operation, areas, and statistics. It is the preferred tool for monitoring and troubleshooting OSPF on Cisco routers.

Question 108: 

A host cannot communicate with devices on a different VLAN. Which configuration is missing?

A) IP address
B) Inter-VLAN routing
C) Trunk configuration on the switch
D) Both B and C

Answer: D

Explanation: 

Communication between VLANs requires a Layer 3 device to perform inter-VLAN routing and a properly configured trunk between the router and switch.

When a host in one VLAN cannot communicate with devices in a different VLAN, the issue is usually related to the lack of Layer 3 routing between VLANs or improper trunk configuration on the switch. VLANs, or Virtual Local Area Networks, segment a physical network into multiple logical networks to improve performance and security. While VLANs isolate broadcast domains, devices in separate VLANs cannot communicate with each other directly without routing.

Inter-VLAN routing is the process that allows traffic to flow between VLANs. It is typically performed by a Layer 3 device such as a router or a Layer 3 switch. Without inter-VLAN routing, hosts in different VLANs remain isolated, even if their individual IP addresses and subnet masks are correctly configureD) Configuring inter-VLAN routing involves creating sub-interfaces on a router or using SVIs (Switched Virtual Interfaces) on a Layer 3 switch, assigning the appropriate IP addresses for each VLAN, and enabling routing between them. This ensures that packets destined for another VLAN are properly forwardeD)

Trunk configuration on the switch is also critical for inter-VLAN communication. A trunk link carries traffic for multiple VLANs over a single physical connection between a switch and a router or between switches. Without a trunk, the VLAN traffic cannot traverse the link, preventing hosts from different VLANs from communicating. Trunking uses protocols such as IEEE 802.1Q to tag frames with their VLAN IDs, allowing the receiving device to identify which VLAN the traffic belongs to.

While assigning an IP address is essential for host communication within a VLAN, it alone does not solve the problem of inter-VLAN communication. The IP address enables hosts to communicate within the same VLAN but does not provide a path to other VLANs.

Therefore, the correct configuration missing is both inter-VLAN routing and trunk configuration on the switch. Both components are required for enabling communication between devices on different VLANs, ensuring that traffic is routed appropriately and VLAN information is preserved across the network.

The correct answer is both B and C)

Question 109: 

Which protocol allows automatic assignment of IP addresses to hosts?

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

Answer: B

Explanation: 

DHCP assigns IP addresses, subnet masks, default gateways, and DNS information automatically, reducing manual configuration errors.

In modern networks, assigning IP addresses to hosts is a fundamental requirement for communication. While IP addresses can be manually configured, this approach is time-consuming and prone to errors, especially in large networks. To simplify this process, the Dynamic Host Configuration Protocol (DHCP) is useD) DHCP automates the assignment of IP addresses, subnet masks, default gateways, and DNS server information to hosts, allowing devices to connect to the network without requiring manual configuration.

When a device joins a network, it broadcasts a DHCP discovery message. A DHCP server responds with an offer that includes an available IP address and other configuration parameters. The host then requests the offered address, and the server acknowledges it, completing the lease process. This dynamic allocation ensures that IP addresses are efficiently managed and reduces the risk of conflicts caused by duplicate addresses. DHCP also allows administrators to manage address allocation centrally, which is especially useful in environments with frequently changing devices such as offices, schools, or public networks.

Other protocols serve different purposes in networking. DNS, or Domain Name System, translates human-readable domain names into IP addresses, allowing users to access websites without remembering numeric IPs. While DNS is essential for name resolution, it does not assign IP addresses to devices. ARP, or Address Resolution Protocol, is used to map IP addresses to MAC addresses within a local network, facilitating communication at the data link layer, but it does not provide IP configuration. ICMP, or Internet Control Message Protocol, is primarily used for diagnostic and error-reporting purposes, such as the ping command, and does not handle IP address assignment either.

By using DHCP, network administrators can ensure that hosts are assigned valid IP configurations automatically, minimizing configuration errors, improving network efficiency, and allowing devices to join and leave the network seamlessly. It is the preferred method for IP management in most modern networks, compared to manual static assignments.

The correct answer is DHCP.

Question 110: 

Which command displays the current spanning-tree root bridge and port roles on a switch?

A) show vlan brief
B) show spanning-tree
C) show running-config
D) show interfaces status

Answer: B

Explanation: 

show spanning-tree displays the root bridge, port roles (root, designated, blocked), and STP status, helping troubleshoot Layer 2 loops.

In a switched network, the Spanning Tree Protocol (STP) is crucial for preventing Layer 2 loops that can cause broadcast storms and network instability. STP ensures there is a single active path between switches while blocking redundant paths until they are needeD) To manage and troubleshoot STP effectively, network administrators need to know which switch is the root bridge and the roles assigned to each port.

The command show spanning-tree is used to display detailed STP information on a switch. When executed, it shows which switch is currently acting as the root bridge, which is the central point of reference for all spanning tree calculations. The command also provides the roles of individual ports, such as root port, designated port, or blocked port. Root ports are those with the best path to the root bridge, designated ports forward traffic for a particular segment, and blocked ports prevent loops by not forwarding frames. Additionally, the command displays STP status, timers, and priority information, helping administrators verify that the spanning tree topology is functioning as intended and troubleshoot potential issues.

Other commands provide different types of information. show vlan brief displays all VLANs configured on the switch, their status, and the ports assigned to each VLAN. While useful for VLAN management, it does not provide STP or root bridge information. show running-config shows the active configuration on the switch, including STP settings if manually configured, but it requires reviewing the configuration manually and does not show real-time STP status or port roles. show interfaces status lists all interfaces along with their operational status, speed, and duplex settings. It is helpful for interface troubleshooting but does not provide information about spanning tree roles or the root bridge.

Therefore, show spanning-tree is the appropriate command for monitoring and verifying the current STP topology. It allows network administrators to identify the root bridge, understand port roles, detect blocked ports, and ensure the network is protected from loops while maintaining connectivity.

The correct answer is show spanning-tree.

Question 111: 

Which feature allows multiple physical links to be combined as a single logical link for redundancy and increased bandwidth?

A) STP
B) EtherChannel
C) VLAN trunking
D) HSRP

Answer: B

Explanation: 

EtherChannel aggregates multiple links, providing higher bandwidth and redundancy while appearing as a single logical interface to the switch.

In network design, increasing bandwidth and providing redundancy between switches or between a switch and a router is often essential to ensure high performance and reliability. One effective way to achieve this is by combining multiple physical links into a single logical connection. This capability is provided by EtherChannel, a feature available on Cisco switches and some other network devices.

EtherChannel allows multiple physical Ethernet links to be bundled together to form one logical interface. From the perspective of the switch or router, the aggregated links appear as a single interface. This provides two main benefits: increased bandwidth and redundancy. Traffic is distributed across the physical links using load-balancing algorithms based on parameters such as source and destination IP addresses, MAC addresses, or Layer 4 port numbers. This increases the overall throughput between devices compared to a single physical link. In addition, if one of the physical links in the EtherChannel bundle fails, traffic is automatically redirected to the remaining active links, providing fault tolerance without disrupting network communication.

Other network features serve different purposes. STP, or Spanning Tree Protocol, is used to prevent loops in Layer 2 networks by blocking redundant paths, but it does not combine links for increased bandwidth. VLAN trunking allows multiple VLANs to share a single physical link by tagging frames with VLAN IDs, facilitating VLAN communication across switches, but it does not provide redundancy or bandwidth aggregation. HSRP, or Hot Standby Router Protocol, provides router redundancy by allowing multiple routers to appear as a single default gateway to hosts, but it does not aggregate links or increase bandwidth.

EtherChannel can be configured using protocols such as PAgP (Port Aggregation Protocol) or LACP (Link Aggregation Control Protocol) to dynamically manage the aggregation, or it can be configured manually as a static bundle. By combining multiple physical interfaces into a single logical link, EtherChannel efficiently increases network capacity, improves redundancy, and simplifies network management.

The correct answer is EtherChannel.

Question 112: 

A router receives a packet for an unknown network. What happens if no default route is configured?

A) Packet is dropped
B) Packet is forwarded to all interfaces
C) ICMP unreachable is sent back
D) Both A and C

Answer: D

Explanation: 

Without a default route, the router cannot forward unknown packets and drops them, sending an ICMP unreachable message to the source.

When a router receives a packet destined for a network that is not listed in its routing table, it must determine how to forward the packet to reach the destination. Routers rely on routing tables to make forwarding decisions, using specific routes for known networks or a default route for unknown destinations. The default route acts as a “catch-all” path, allowing the router to forward packets even when the destination network is not explicitly listed in the routing table.

If no default route is configured and the router does not have a specific route for the destination network, it cannot forward the packet. In this case, the router drops the packet to prevent it from circulating endlessly in the network. Dropping the packet ensures that network resources are not wasted on traffic that cannot reach its destination.

Additionally, when a router drops a packet due to an unknown destination, it usually generates an ICMP (Internet Control Message Protocol) destination unreachable message back to the source host. This informs the sender that the packet could not be delivered, allowing the source device to take appropriate action, such as notifying the user or attempting an alternative route if available. The ICMP unreachable message is essential for network troubleshooting and maintaining proper communication between hosts.

Other options in this scenario are not accurate. Forwarding the packet to all interfaces, also known as flooding, occurs in some Layer 2 protocols like ARP, but it is not done at Layer 3 for IP routing. Simply dropping the packet without notifying the source would prevent the sender from knowing that delivery failed, which is why routers send the ICMP unreachable message as part of standard IP behavior.

In summary, when a router receives a packet for an unknown network and no default route is configured, it cannot forward the packet. The router drops the packet and sends an ICMP destination unreachable message to the source, providing both protection for the network and feedback to the sender.

The correct answer is both A and C)

Question 113: 

Which IPv6 address type is used to identify multiple devices, with packets delivered to the nearest device only?

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

Answer: C

Explanation: 

Anycast addresses allow multiple devices to share the same address, with traffic routed to the nearest device based on routing metrics.

IPv6 introduces several types of addresses to support different communication scenarios, including unicast, multicast, anycast, and link-local addresses. Each address type serves a specific purpose in delivering packets efficiently across networks.

Anycast addresses are designed to identify multiple devices using the same IPv6 address. When a packet is sent to an anycast address, the network delivers it to the “nearest” device in terms of routing distance or metrics, rather than to all devices sharing that address. This provides an efficient way to direct traffic to a service that is replicated across multiple locations, such as DNS servers or content delivery nodes, ensuring low latency and improved performance. Anycast is widely used in scenarios where redundancy and load distribution are important, as it allows multiple devices to respond to requests without the sender needing to know their individual addresses.

Unicast addresses, by contrast, are assigned to a single interface, and packets sent to a unicast address are delivered directly to that specific interface. This is the most common type of IPv6 address used for standard one-to-one communication between hosts. Multicast addresses are used for one-to-many communication, delivering packets to all devices that have joined a particular multicast group. This is useful for applications like streaming or network discovery, where multiple recipients need to receive the same data simultaneously. Link-local addresses are automatically assigned to interfaces and are used for communication between devices on the same link or subnet. They are not routable beyond the local link and are essential for functions such as neighbor discovery and routing protocol operations.

Unlike unicast or multicast, anycast addresses uniquely combine the benefits of redundancy and efficient routing. They allow multiple devices to share a single address while ensuring that packets are routed to the optimal device based on network topology and routing metrics. This makes anycast ideal for distributed services where minimizing latency and improving reliability are critical.

The correct answer is anycast.

Question 114: 

Which command verifies which routes were learned via EIGRP?

A) show ip route eigrp
B) show ip eigrp neighbors
C) show running-config
D) show interfaces

Answer: A

Explanation: 

show ip route eigrp displays all EIGRP-learned routes in the routing table, including next hops and outgoing interfaces.

Enhanced Interior Gateway Routing Protocol (EIGRP) is an advanced distance-vector routing protocol that enables routers to exchange routing information efficiently within an autonomous system. When configuring or troubleshooting EIGRP, network administrators often need to verify which routes a router has learned from its EIGRP neighbors. Cisco provides several commands for this purpose, each serving a specific role in monitoring and managing the protocol.

The command show ip route eigrp is specifically used to display all routes learned via EIGRP that are currently installed in the router’s IP routing table. When executed, it lists the networks, their associated next-hop addresses, and the outgoing interfaces through which packets for those networks should be forwardeD) This command is crucial for confirming that EIGRP is correctly exchanging routing information with neighboring routers and for verifying that the expected networks are reachable. It also helps in troubleshooting routing issues, such as missing routes or unexpected routing paths, by providing a clear view of EIGRP’s contribution to the routing table.

Other commands provide complementary information but do not show EIGRP-learned routes in the routing table. show ip eigrp neighbors displays a list of directly connected EIGRP neighbors along with their IP addresses, interface information, and EIGRP uptime. This command is useful for verifying neighbor relationships and ensuring that EIGRP adjacencies are established correctly, but it does not show which routes have been learned or installed in the routing table. show running-config displays the active configuration on the router, including EIGRP network statements, interface settings, and other configurations, but it requires manual inspection to infer learned routes. show interfaces lists all interfaces on the router with their operational status, IP addresses, and statistics, which is helpful for interface troubleshooting but does not provide any routing information.

The correct answer is show ip route eigrp.

Question 115:

Which type of NAT maps one private IP to one public IP permanently?

A) Static NAT
B) Dynamic NAT
C) PAT
D) Overloading NAT

Answer: A

Explanation: 

Static NAT creates a permanent one-to-one mapping between a private and a public IP, typically used for servers needing a fixed public IP.

Network Address Translation (NAT) is a crucial mechanism in networking that allows private IP addresses within an internal network to communicate with external networks, such as the internet. NAT provides security by hiding internal addresses and conserves public IP addresses by translating multiple private addresses into fewer public addresses. There are several types of NAT, each serving different purposes depending on the network requirements.

Static NAT is a type of NAT that creates a permanent, one-to-one mapping between a private IP address and a public IP address. This ensures that a specific internal host always uses the same public IP when communicating with external networks. Static NAT is commonly used for servers, such as web, mail, or FTP servers, that require a consistent public IP address so that external clients can reliably reach them. Because the mapping is fixed, the public IP is reserved for that internal host, providing predictable connectivity.

Dynamic NAT, on the other hand, maps private IP addresses to public IP addresses from a pool of available addresses. Unlike static NAT, the mappings are temporary and created on a first-come, first-served basis. Once a session ends or the NAT entry expires, the public IP becomes available for other devices. Dynamic NAT is suitable for general hosts that do not require a fixed public IP.

PAT, or Port Address Translation, also known as NAT overloading, allows multiple private IP addresses to share a single public IP address by differentiating sessions based on port numbers. This is the most common type of NAT used in home networks and small offices because it conserves public IP addresses efficiently while allowing multiple devices to access the internet simultaneously.

In summary, while dynamic NAT and PAT provide flexible and efficient use of public IP addresses, static NAT is specifically designed to provide a permanent one-to-one mapping between a private and a public IP. This makes it ideal for servers and devices that require a fixed, reachable public IP address.

The correct answer is static NAT.

Question 116: 

Which protocol is used to send error messages and operational information about IP processing?

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

Answer: A

Explanation: 

ICMP communicates errors such as unreachable hosts, network congestion, or time exceeded, and is also used for testing connectivity (ping).

The Internet Control Message Protocol (ICMP) is an integral part of the Internet Protocol (IP) suite that provides feedback about issues in the communication environment. Unlike protocols that transport user data, such as TCP or UDP, ICMP is primarily used for sending control messages and error notifications related to IP processing. It allows devices like routers, switches, and hosts to communicate information about network conditions, helping administrators and systems troubleshoot connectivity problems.

ICMP is responsible for reporting various types of errors. For example, it notifies a sender when a destination host is unreachable due to network or host issues, when a router cannot forward a packet because of congestion, or when the time-to-live (TTL) field of a packet expires. This error-reporting capability is essential for maintaining reliable network operations, as it enables devices to adjust routing decisions or notify applications of delivery failures. ICMP also supports operational testing functions. Tools like ping use ICMP echo request and echo reply messages to verify whether a host is reachable and measure round-trip times. Similarly, traceroute leverages ICMP to determine the path packets take through a network, providing visibility into intermediate hops.

Other protocols serve different purposes. ARP, or Address Resolution Protocol, is used to map IP addresses to MAC addresses within a local network, facilitating Layer 2 communication, but it does not provide error messages or operational feedback about IP routing. DHCP, or Dynamic Host Configuration Protocol, automatically assigns IP addresses and network configuration to hosts, simplifying IP management but not handling connectivity issues. DNS, or Domain Name System, resolves human-readable domain names into IP addresses, enabling users to access websites without remembering numeric addresses, but it does not report network errors.

In summary, ICMP is the protocol specifically designed to send error messages and operational information regarding IP processing. By providing feedback on unreachable hosts, network congestion, and other issues, as well as supporting connectivity tests, ICMP is vital for diagnosing and maintaining a healthy IP network.

The correct answer is ICMP.

Question 117: 

Which Layer 2 protocol prevents loops in networks with redundant links?

A) RIP
B) OSPF
C) STP
D) BGP

Answer: C

Explanation: 

Spanning Tree Protocol detects redundant paths and blocks some ports to prevent broadcast loops while keeping at least one active path.

In Ethernet networks, having redundant links between switches is a common practice to provide fault tolerance and maintain connectivity if a link fails. However, these redundant links can create broadcast loops at Layer 2, where frames circulate endlessly between switches. Such loops can cause network congestion, degraded performance, and even complete network outages. To address this issue, the Spanning Tree Protocol (STP) is useD)

STP is a Layer 2 protocol designed to prevent loops in networks with redundant links. It works by electing a root bridge and then calculating the shortest path from each switch to the root bridge. STP assigns roles to switch ports, such as root port, designated port, or blocked port, and selectively blocks certain redundant paths while keeping at least one active path for network connectivity. This ensures that traffic is forwarded efficiently without creating loops, while still allowing backup paths to become active if a primary link fails.

Other protocols in the options serve different purposes. RIP, or Routing Information Protocol, is a Layer 3 distance-vector routing protocol that determines paths between networks based on hop count. It does not operate at Layer 2 and therefore cannot prevent switching loops. OSPF, or Open Shortest Path First, is another Layer 3 routing protocol that uses a link-state algorithm to calculate the best paths between networks. Like RIP, OSPF deals with routing between subnets and has no mechanism to prevent Layer 2 loops. BGP, or Border Gateway Protocol, is an exterior gateway protocol used to exchange routing information between autonomous systems on the internet. BGP operates at Layer 3 and focuses on path selection based on policies rather than addressing Layer 2 network loops.

In summary, among the protocols listed, only STP is specifically designed to prevent loops at Layer 2 in networks with redundant links. By blocking some ports while maintaining at least one active path, STP ensures stable Layer 2 network operation, preventing broadcast storms and maintaining reliable connectivity.

The correct answer is STP.

Question 118: 

A network engineer wants to verify which VLANs are allowed on a trunk interface. Which command should be used?

A) show vlan brief
B) show interfaces trunk
C) show running-config
D) show spanning-tree

Answer: B

Explanation: 

show interfaces trunk displays trunk status, allowed VLANs, native VLAN, and encapsulation on trunk ports.

Question 119: 

Which command displays all MAC addresses learned by a switch and their associated ports?

A) show interfaces
B) show mac-address-table
C) show vlan brief
D) show ip route

Answer: B

Explanation: 

show mac-address-table lists all MAC addresses learned by the switch and the ports they were learned on, useful for troubleshooting Layer 2 connectivity.

Question 120: 

A network engineer wants to monitor network devices and receive alerts for abnormal events. Which protocol is commonly used?

A) FTP
B) SNMP
C) ICMP
D) ARP

Answer: B

Explanation: SNMP (Simple Network Management Protocol) allows monitoring and management of network devices, including alerting administrators to abnormal events and performance issues.