200-301 Cisco Certified Network Associate (CCNA) Exam Dumps and Practice Test Questions Set 5 Q81-100

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Question 81: 

A network engineer wants to block all HTTP traffic but allow all other protocols. Which type of ACL should be used?

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

Answer: B

Explanation: 

Extended ACLs can filter traffic based on source, destination, protocol, and port numbers. Blocking HTTP requires filtering TCP traffic on port 80, which cannot be done with a standard ACL.

Access Control Lists (ACLs) are used in networking to control traffic entering or leaving a network interface. When a network engineer wants to block specific types of traffic, the type of ACL chosen determines the level of control available. In the scenario of blocking all HTTP traffic while allowing all other protocols, an extended ACL is the appropriate choice. Extended ACLs allow filtering based on multiple criteria, including source and destination IP addresses, Layer 3 protocols, and Layer 4 port numbers. Since HTTP traffic uses TCP port 80, an extended ACL can be configured to specifically deny TCP traffic on this port while permitting all other traffic, providing precise control over network access.

Option A, a standard ACL, only filters traffic based on the source IP address. Standard ACLs do not consider the destination address, protocol type, or port number. Therefore, they cannot selectively block HTTP traffic, as HTTP is defined by a combination of protocol (TCP) and port number (80). Standard ACLs are suitable for very basic filtering, such as restricting access to a network segment based on source addresses.

Option C, reflexive ACLs, are dynamic ACLs that track outbound sessions and permit the corresponding inbound return traffiC) They provide temporary, stateful filtering and are often used for security purposes, such as controlling sessions initiated from inside the network. Reflexive ACLs are not necessary for simply blocking a well-known protocol like HTTP.

Option D, named ACLs, are simply ACLs assigned a descriptive name instead of a numeric identifier. Named ACLs can be standard or extended, so while naming makes them easier to manage, it does not define the filtering capability on its own. To block HTTP traffic, the ACL must be an extended type, whether it is named or numbereD)

Question 82: 

Which command displays the status of EtherChannel interfaces on a Cisco switch?

A) show interfaces
B) show etherchannel summary
C) show running-config
D) show mac-address-table

Answer: B

Explanation: 

show etherchannel summary displays all EtherChannel groups, their operational status, protocol, and member interfaces, useful for troubleshooting bundled links.

EtherChannel is a Cisco technology that allows multiple physical links to be bundled into a single logical link to provide higher bandwidth and redundancy between switches or routers. To effectively manage and troubleshoot EtherChannel configurations, it is important to verify the operational status of the aggregated interfaces. The Cisco IOS command show etherchannel summary is specifically designed for this purpose. This command provides a concise overview of all EtherChannel groups configured on the switch, displaying information such as the group number, protocol used for negotiation (PAgP or LACP), operational status, and the member interfaces that make up each channel. By examining this output, network administrators can quickly identify whether an EtherChannel is up, which links are active, and whether the protocol is correctly configureD) This is crucial for ensuring optimal link utilization and redundancy.

Option A, show interfaces, displays detailed information about individual physical and logical interfaces, including status, IP addresses, bandwidth, and errors. While this command is useful for troubleshooting single interfaces, it does not provide a summarized view of EtherChannel groups or show the relationship between the member interfaces and the logical channel.

Option C, show running-config, shows the current configuration of the switch, including interface settings and EtherChannel configuration commands. Although it provides information on how the EtherChannel is configured, it does not display the real-time operational status or whether the individual links are successfully bundled and active.

Option D, show mac-address-table, displays the MAC addresses learned on the switch and the corresponding ports. This command is helpful for verifying device connectivity but does not provide any information about EtherChannel groups or their operational status.

Question 83: 

A host cannot reach the default gateway. Which of the following is the most likely cause?

A) Incorrect IP address on the host
B) Host is in a different VLAN than the gateway
C) Gateway interface is down
D) Any of the above

Answer: D

Explanation: 

Communication with the default gateway requires correct IP addressing, the host and gateway must be in the same VLAN or routed properly, and the gateway interface must be operational.

When a host cannot reach its default gateway, several potential causes must be considered, as multiple factors affect connectivity to the gateway. The default gateway is the router interface that connects the host’s local network to other networks, and proper communication with it is essential for accessing devices outside the host’s subnet.

Option A, an incorrect IP address on the host, is a common cause of connectivity issues. If the host’s IP address is misconfigured, it may not be in the same subnet as the default gateway, preventing proper Layer 3 communication. For example, if the host’s IP address or subnet mask is incorrect, packets may not be routed correctly to the gateway, resulting in failed pings or unreachable destinations.

Option B, the host being in a different VLAN than the gateway, can also prevent connectivity. VLANs create separate broadcast domains, and communication between devices in different VLANs requires routing. If a host is assigned to a VLAN that does not match the VLAN of the gateway interface, it cannot reach the gateway unless inter-VLAN routing is properly configured on a Layer 3 device such as a router or Layer 3 switch.

Option C, the gateway interface being down, is another possible reason. If the router or switch interface serving as the default gateway is administratively shut down or experiencing a physical failure, the host will be unable to reach it. The interface must be operational, with an IP address assigned and the link active, for successful communication.

Considering all these possibilities, the correct answer is option D, any of the above. Connectivity issues to the default gateway can result from IP misconfiguration, VLAN mismatches, or a non-functional gateway interface. Network administrators must verify that the host has a correct IP address and subnet mask, ensure that it is in the same VLAN as the gateway or that proper routing exists, and confirm that the gateway interface is active to restore communication.

Question 84: 

Which type of NAT maps multiple private addresses to a single public address using different port numbers?

A) Static NAT
B) Dynamic NAT
C) PAT (Port Address Translation)
D) Dual NAT

Answer: C

Explanation: 

PAT, also called NAT overload, allows multiple private IP addresses to share a single public IP address using unique TCP/UDP port numbers.

Network Address Translation (NAT) is a technique used to translate private IP addresses used within a local network to public IP addresses that can be routed on the internet. One common scenario is when multiple devices in a private network need to access the internet using a single public IP address. Port Address Translation (PAT), also known as NAT overload, is the type of NAT designed specifically for this purpose. PAT allows multiple private IP addresses to be mapped to a single public IP address by assigning a unique TCP or UDP port number to each session. This ensures that return traffic can be correctly routed back to the originating host, even though all devices are sharing the same public IP address. PAT is widely used in home and enterprise networks because it conserves public IP addresses while allowing multiple users to access external resources simultaneously.

Option A, Static NAT, provides a one-to-one mapping between a private IP address and a public IP address. Each internal host is permanently assigned a specific public IP address. While this is useful for hosting servers that must be consistently reachable from the internet, it does not allow multiple hosts to share a single public IP.

Option B, Dynamic NAT, maps private addresses to a pool of available public addresses on a first-come, first-served basis. Each private address is translated to a public address from the pool when needeD) Unlike PAT, dynamic NAT still requires multiple public addresses to accommodate multiple internal hosts.

Option D, Dual NAT, is not a standard term in networking. NAT typically refers to either static, dynamic, or PAT/NAT overload, so dual NAT is not applicable in this context.

In summary, PAT is the correct solution when multiple private IP addresses need to share a single public IP address. By using unique port numbers, PAT enables many internal devices to communicate with external networks efficiently, making it an essential technology for IP address conservation and internet connectivity in modern networks.

Question 85: 

Which protocol is used to synchronize time on network devices?

A) DNS
B) NTP
C) DHCP
D) SNMP

Answer: B

Explanation: 

NTP (Network Time Protocol) synchronizes the clocks of network devices to ensure consistent timestamps for logs, authentication, and scheduled tasks.

In a network, maintaining accurate time across all devices is critical for troubleshooting, log correlation, authentication, and scheduled tasks. Network Time Protocol (NTP) is the protocol specifically designed to synchronize the clocks of network devices. NTP operates over the network to provide consistent and accurate time to routers, switches, servers, and other devices. By synchronizing to a reliable reference clock, such as an atomic clock or a GPS-based time source, NTP ensures that timestamps across devices are consistent, which is essential for network management, security auditing, and event correlation. Without accurate time synchronization, logs from different devices can show conflicting timestamps, making it difficult to trace network events or identify security incidents.

Option A, DNS (Domain Name System), translates human-readable domain names into IP addresses to enable communication across networks. While DNS is essential for locating devices and services by name, it does not provide time synchronization and cannot be used to align clocks on network devices.

Option C, DHCP (Dynamic Host Configuration Protocol), is used to automatically assign IP addresses and other network configuration parameters to hosts. DHCP ensures devices can join a network with proper settings, but it does not synchronize clocks or maintain consistent time across devices.

Option D, SNMP (Simple Network Management Protocol), is used for monitoring and managing network devices. SNMP allows administrators to collect performance metrics, configure devices, and receive alerts. While SNMP provides management capabilities, it is not intended for time synchronization.

In summary, NTP is the protocol used to synchronize time on network devices. By providing accurate and consistent time, NTP supports log consistency, security auditing, authentication processes, and scheduled network tasks. Accurate time synchronization is a fundamental requirement for effective network operations and troubleshooting, making NTP an essential protocol in enterprise and service provider networks.

Question 86: 

Which Cisco IOS command enables logging of events related to network security or failures?

A) logging buffered
B) show logging
C) debug all
D) log event

Answer: A

Explanation: 

logging buffered stores log messages in memory for later review. Combined with show logging, it helps network engineers monitor network events and troubleshoot issues.

In network management, monitoring and logging events is critical for troubleshooting, security auditing, and maintaining the health of network devices. Cisco IOS provides a set of commands to manage logging on routers and switches. The command logging buffered is used to enable the storage of log messages in the device’s RAM. When this command is configured, the router or switch records messages related to system events, security issues, interface changes, routing updates, and failures in a local buffer. These messages are stored temporarily in memory, allowing network engineers to review them at a later time. This is especially useful for identifying the root causes of network outages, configuration errors, or unauthorized access attempts.

Option B, show logging, does not enable logging but is used to display the contents of the logging buffer. After logging buffered is configured, the show logging command allows administrators to review the stored messages, providing insight into recent events and facilitating troubleshooting. While it is essential for monitoring, it cannot independently capture or store logs without logging being enableD)

Option C, debug all, enables real-time debugging for almost all processes on a device. While powerful for detailed troubleshooting, this command is highly resource-intensive and can impact device performance. It also produces a large volume of messages, which can be overwhelming and is generally not recommended for continuous logging in production environments.

Option D, log event, is not a valid Cisco IOS command for enabling logging. While it may sound intuitive, Cisco devices use specific commands such as logging buffered, logging console, or logging monitor to configure event logging.

In summary, logging buffered is the correct command to enable logging of events related to network security or failures. By storing messages in memory, it allows administrators to monitor network behavior, review historical events, and troubleshoot problems efficiently, especially when combined with the show logging command for viewing recorded messages.

Question 87: 

Which type of IPv6 address is automatically configured on every interface for local communications?

A) Global unicast
B) Link-local
C) Multicast
D) Anycast

Answer: B

Explanation: 

Link-local addresses (FE80::/10) are automatically assigned to all IPv6 interfaces and are used for local link communications, such as routing protocols or neighbor discovery.

In IPv6 networking, each interface is automatically assigned a link-local address, which is essential for communication on the local link. Link-local addresses fall within the FE80::/10 prefix and are automatically configured on every IPv6-enabled interface without the need for manual assignment or DHCPv6. These addresses are used for local communications between devices on the same physical or logical link, such as neighbor discovery, routing protocol exchanges, and other link-specific operations. Because link-local addresses are only valid on the local segment, they cannot be routed across different networks, making them ideal for internal link communications.

Option A, global unicast addresses, are similar to IPv4 public addresses. They are globally unique and routable across the internet. Global unicast addresses are not automatically configured on every interface, and their assignment typically requires either manual configuration or the use of stateless or stateful address configuration protocols, such as SLAAC or DHCPv6. These addresses are intended for communication beyond the local link.

Option C, multicast addresses, allow a single packet to be delivered to multiple interfaces that have joined a multicast group. Multicast addresses are used for group communication, such as OSPFv3 routing updates or sending data to multiple receivers simultaneously. Multicast addresses are not automatically assigned to every interface for general local communication.

Option D, anycast addresses, are assigned to multiple interfaces, usually on different devices, but traffic sent to an anycast address is delivered to the nearest interface based on routing distance. Anycast addresses are manually configured for specific use cases, such as providing redundancy for services, and are not automatically assigned to all interfaces.

In summary, link-local addresses are the IPv6 address type that is automatically assigned to every interface and is essential for local link operations. They enable devices to communicate on the same segment without requiring a globally routable address, providing the foundation for neighbor discovery, routing protocol exchanges, and other local IPv6 operations.

Question 88: 

A network engineer wants to ensure a router will prefer a static route over a dynamically learned route. Which parameter can be modified?

A) Administrative distance
B) Metric
C) Hop count
D) Subnet mask

Answer: A

Explanation: 

Administrative distance determines the trustworthiness of a route. Lower administrative distance is preferreD) Static routes default to 1, which is usually preferred over dynamic protocols.

In routing, when a router learns about the same destination network from multiple sources, it must decide which route to use for forwarding traffiC) This decision is influenced by the administrative distance (AD), a parameter that represents the trustworthiness or reliability of a route source. Each routing protocol and type of route is assigned a default administrative distance. Static routes, by default, have an AD of 1, making them more trustworthy than most dynamic routing protocols, which have higher AD values. For example, OSPF has a default AD of 110, EIGRP has 90, and RIP has 120. By comparing the administrative distance, a router will prefer the route with the lowest AD, ensuring that static routes are selected over dynamically learned routes when both exist. Network engineers can also manually adjust the administrative distance to influence route preference further, allowing precise control over routing decisions.

Option B, metric, is used within a routing protocol to determine the best path to a destination among multiple possible paths learned by the same protocol. Metrics vary depending on the protocol—for instance, OSPF uses cost based on bandwidth, EIGRP uses a composite metric including bandwidth and delay, and RIP uses hop count. While metrics influence path selection within a single protocol, they do not override the administrative distance between different types of routes. Therefore, adjusting the metric cannot ensure a static route is preferred over a dynamic route from a different protocol.

Option C, hop count, is a simple measure of the number of routers a packet must pass through to reach a destination. Hop count is primarily used by protocols like RIP to determine the best path. Modifying hop count does not change the trustworthiness of a route compared to other routing sources and cannot guarantee that a static route will be preferred over a dynamic one.

Option D, subnet mask, defines the network and host portions of an IP address and affects address summarization and reachability. Changing the subnet mask does not influence route preference between static and dynamic routes.

In summary, administrative distance is the key parameter that determines which route a router prefers when multiple sources provide paths to the same destination. Lower administrative distance values are considered more reliable, allowing static routes to take precedence over dynamic routes.

Question 89: 

Which of the following is a benefit of using VLANs in a network?

A) Reduces broadcast domains
B) Provides redundancy
C) Increases bandwidth of physical links
D) Encrypts traffic

Answer: A

Explanation: 

VLANs segment a network into multiple broadcast domains, reducing unnecessary broadcast traffic and improving network efficiency.

Virtual Local Area Networks (VLANs) are a key technology used in modern network design to segment a physical network into multiple logical networks. One of the primary benefits of VLANs is that they reduce the size of broadcast domains. In a traditional flat network, all devices connected to a switch share the same broadcast domain, meaning that broadcast traffic from any device is received by all other devices in the network. This can lead to network congestion and decreased efficiency as the number of devices increases. By creating VLANs, a network can be divided into smaller, logical segments where each VLAN functions as its own separate broadcast domain. This segmentation limits the scope of broadcast traffic, reducing unnecessary network load and improving overall performance.

Option B, providing redundancy, is not a direct benefit of VLANs. Redundancy is typically achieved through protocols such as Spanning Tree Protocol (STP) or by deploying multiple links and devices for failover. While VLANs can be part of a design that includes redundancy, VLANs themselves do not inherently provide redundant paths.

Option C, increasing the bandwidth of physical links, is also not a direct benefit of VLANs. VLANs logically segment traffic without changing the physical bandwidth of links. Techniques such as link aggregation or EtherChannel are used to increase physical link bandwidth.

Option D, encrypting traffic, is another feature that VLANs do not provide. While VLANs isolate traffic at Layer 2, they do not encrypt it. Encryption must be implemented through protocols such as IPsec, SSL, or MACsec to ensure data confidentiality.

In summary, the main benefit of using VLANs is the reduction of broadcast domains. By dividing a network into smaller logical segments, VLANs improve efficiency, reduce broadcast traffic, enhance security through segmentation, and allow for better network management and organization. This makes VLANs an essential tool for optimizing performance in medium to large-scale networks.

Question 90: 

Which command displays all OSPF LSAs on a router?

A) show ip route ospf
B) show ip ospf database
C) show ip ospf neighbor
D) show running-config

Answer: B

Explanation: 

show ip ospf database displays the link-state advertisements (LSAs) that OSPF routers exchange to build a complete topology database.

Open Shortest Path First (OSPF) is a link-state routing protocol in which routers share detailed information about network topology to calculate the shortest paths to all destinations. This information is shared using Link-State Advertisements (LSAs). LSAs describe the state of each router’s links, including connected networks, costs, and other routing information. To verify and examine these advertisements, Cisco routers provide the command show ip ospf database. This command displays all LSAs that the router has received from other OSPF routers, allowing network administrators to view the complete topology database. By analyzing this information, engineers can troubleshoot routing issues, verify network connectivity, and confirm that the OSPF network has converged properly.

Option A, show ip route ospf, displays all routes in the routing table that were learned via OSPF. While this command is useful for confirming which networks are reachable through OSPF, it does not provide details about the individual LSAs or the topology database itself. It only shows the final paths chosen for routing.

Option C, show ip ospf neighbor, displays information about OSPF neighbors, including their IP addresses, interface, and the state of adjacency. This command is important for verifying that OSPF routers have successfully formed neighbor relationships, but it does not show the LSAs or the network topology details.

Option D, show running-config, displays the current configuration of the router, including OSPF process settings, network statements, and interface configurations. While it helps review OSPF settings, it does not display the dynamically exchanged LSAs or the router’s link-state database.

In summary, the show ip ospf database command is the correct choice for displaying all OSPF LSAs on a router. It provides a detailed view of the OSPF topology, including all routers and networks, enabling network administrators to understand how routing information is distributed and to troubleshoot or optimize OSPF operations effectively.

Question 91: 

Which Cisco IOS command verifies which devices are connected to each switch port based on MAC addresses?

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

Answer: B

Explanation: 

show mac-address-table lists all MAC addresses learned by the switch and the ports on which they were learned, helping troubleshoot connectivity.In a switched network, knowing which devices are connected to which ports is essential for troubleshooting, security, and network management. Cisco switches maintain a MAC address table, which maps each learned MAC address to the specific switch port through which the device is connecteD) The Cisco IOS command show mac-address-table is used to verify this information. When executed, this command displays all MAC addresses that the switch has learned, along with the corresponding interface or port and VLAN. This information allows network engineers to determine which devices are physically connected to specific ports, identify unauthorized devices, detect network loops, and troubleshoot connectivity issues.

Option A, show interfaces, provides detailed information about the physical and logical status of each interface, including operational status, bandwidth, duplex settings, and errors. While this command is useful for verifying that interfaces are up and functioning correctly, it does not show which devices are connected or their MAC addresses.

Option C, show vlan brief, displays all VLANs configured on the switch, their status, and the ports assigned to each VLAN. While it helps verify VLAN assignments, it does not provide information about the actual devices connected to each port or their MAC addresses.

Option D, show arp, displays the IP-to-MAC address mapping learned by the router or Layer 3 switch. While ARP tables can help track device IPs on a network segment, they only include IP addresses and corresponding MAC addresses and are limited to devices that have communicated with the router. ARP does not show which physical switch port a device is connected to, making it less useful for port-level troubleshooting.

In summary, the show mac-address-table command is the primary tool for verifying which devices are connected to each switch port. By displaying MAC addresses, associated ports, and VLANs, it provides a clear and actionable view of the switch’s Layer 2 connectivity, aiding in troubleshooting, security monitoring, and overall network management.

Question 92: 

Which protocol allows routers to exchange reachability information across autonomous systems?

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

Answer: C

Explanation: 

BGP (Border Gateway Protocol) is an inter-domain protocol used between autonomous systems to exchange routing information on the internet.

Border Gateway Protocol (BGP) is the standard protocol used to exchange routing information between different autonomous systems (ASes) on the internet. An autonomous system is a collection of IP networks under a single administrative domain, typically managed by an Internet Service Provider (ISP) or a large organization. BGP is classified as an exterior gateway protocol (EGP) and is essential for inter-domain routing. It allows routers in different ASes to share information about which networks are reachable, enabling the internet to function as a global, interconnected network. BGP uses path vector routing, making decisions based on policies, AS-path information, and attributes such as next-hop and route origin, rather than relying solely on metrics like hop count or bandwidth.

Option A, OSPF (Open Shortest Path First), is a link-state interior gateway protocol (IGP) used to exchange routing information within a single autonomous system. OSPF supports hierarchical network designs using areas to optimize routing and reduce the size of routing tables, but it is not designed for exchanging routes between autonomous systems.

Option B, EIGRP (Enhanced Interior Gateway Routing Protocol), is a Cisco proprietary protocol that operates as an IGP. EIGRP efficiently shares routing information within a single AS using a composite metric based on bandwidth, delay, reliability, and loaD) Like OSPF, EIGRP does not provide a mechanism for inter-domain routing between autonomous systems.

Option D, RIP (Routing Information Protocol), is a distance-vector protocol used primarily within small to medium-sized networks. RIP exchanges routing information based on hop count but is limited in scalability and cannot exchange routing information across autonomous systems.

In summary, BGP is the protocol specifically designed to allow routers to exchange reachability information across autonomous systems. It ensures that routers in different administrative domains can communicate and route traffic efficiently across the internet. While OSPF and EIGRP are effective for routing within an AS, and RIP is limited to small networks, only BGP provides the policy-based, scalable framework required for inter-domain connectivity.

Question 93: 

A switchport is configured with switchport mode access and switchport port-security maximum 2. What happens if a third device connects?

A) The port shuts down if violation mode is shutdown
B) The traffic from the third device is dropped
C) The violation is logged
D) All of the above

Answer: D

Explanation: 

Port security enforces limits on the number of allowed MAC addresses. Depending on violation mode (shutdown, restrict, or protect), the port may shut down, drop traffic, and log events.

Port security is a feature on Cisco switches that helps protect the network by controlling which devices are allowed to connect to a switch port based on their MAC addresses. In the scenario where a switchport is configured with switchport mode access and switchport port-security maximum 2, the port is limited to allowing only two unique MAC addresses. This ensures that only two devices can communicate through the port at any given time. If a third device is connected to the port, the switch detects a violation of the port security settings.

Option A explains that if the violation mode is set to shutdown, the port will automatically shut down when the third device is detecteD) This is the default violation mode for port security. The shutdown mode ensures maximum protection by disabling the interface, preventing any unauthorized access, and requiring manual intervention or re-enabling of the port.

Option B describes that the traffic from the third device will be droppeD) This occurs when the violation mode is set to protect or restrict. In protect mode, the switch silently drops frames from unauthorized devices without affecting the operation of the port for authorized devices. In restrict mode, traffic from the unauthorized device is dropped, but the switch also generates a log entry and increments a security violation counter.

Option C highlights that the violation is loggeD) Logging is an essential part of port security because it allows network administrators to track unauthorized access attempts, monitor security events, and take corrective action if needeD) Depending on the violation mode, these events can be sent to the console, syslog server, or stored locally on the switch for later review.

Considering all these behaviors, option D is correct. When the port is configured for a maximum of two MAC addresses, connecting a third device can trigger all of the above actions: the port may shut down, the traffic may be dropped, and the violation event may be loggeD) The exact response depends on the configured violation mode, allowing network engineers to tailor security according to the network requirements.

Question 94: 

Which IPv6 address is used to send packets to all interfaces on a local network segment?

A) FF02::1
B) FF02::2
C) FE80::1
D) FF00::1

Answer: A

Explanation: 

FF02::1 is the all-nodes multicast address in IPv6, reaching all nodes on the local link.

In IPv6 networking, multicast addresses are used to efficiently deliver packets to multiple devices without sending individual copies to each node. One important multicast address is FF02::1, known as the all-nodes multicast address. This address is link-local, meaning it is used only within the local network segment and does not traverse routers. When a packet is sent to FF02::1, it is delivered to every IPv6-enabled interface on the same link. This makes it ideal for scenarios where a message needs to reach all devices on a local network segment, such as during network discovery or protocol operations like Neighbor Discovery Protocol (NDP).

Option B, FF02::2, is the all-routers multicast address. Packets sent to FF02::2 are delivered to all routers on the local link rather than all nodes. This address is used for protocols or processes that require communication specifically with routers, such as routing protocol updates or router advertisements. Unlike FF02::1, it does not reach end-host devices that are not routers.

Option C, FE80::1, is an example of a link-local unicast address. Link-local addresses, in general, are automatically assigned to each IPv6 interface and are used for direct communication between two devices on the same link. Unlike multicast addresses, FE80::1 targets a single interface rather than all interfaces on the segment, so it cannot be used to reach all devices simultaneously.

Option D, FF00::1, is not a valid standard multicast address for IPv6. Multicast addresses in IPv6 are designated within the range FF00::/8, but FF00::1 does not correspond to any defined all-nodes or all-routers multicast group. Therefore, it cannot be used to reach all devices on a local segment.

In summary, FF02::1 is the correct IPv6 address used to send packets to all interfaces on a local link. It ensures that messages are delivered efficiently to every IPv6-enabled node on the network segment, which is critical for processes such as neighbor discovery, local link announcements, and network-wide communication within a single subnet.

Question 95:

A router interface is configured with ip address 192.168.1.1 255.255.255.0. Which command verifies the interface status and IP?

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

Answer: B

Explanation: 

show ip interface brief provides a concise overview of interfaces, IP addresses, and operational status, allowing quick verification of connectivity configuration.

When configuring a router interface with an IP address, it is important to verify both the IP configuration and the operational status of the interface to ensure proper connectivity. For example, if a router interface is configured with ip address 192.168.1.1 255.255.255.0, the command show ip interface brief is the most efficient way to check the interface. This command provides a concise summary of all router interfaces, including IP addresses, interface status (administratively up or down), and protocol status (up or down). By using this command, network engineers can quickly confirm that the interface is correctly configured and operational, allowing devices on the network to communicate with the router without issues.

Option A, show running-config, displays the current configuration of the router, including IP addresses, routing protocols, access lists, and other settings. While this command can show how the interface is configured, it does not provide real-time operational status, meaning an interface could be administratively up but physically down or experiencing problems, and this would not be immediately obvious from the configuration output.

Option C, show ip route, displays the router’s routing table, including directly connected networks, static routes, and dynamically learned routes. This command is useful for verifying network reachability and troubleshooting routing issues, but it does not provide direct information about the operational state of an interface or whether the configured IP address is active.

Option D, show arp, displays the IP-to-MAC address mappings that the router has learned for devices on its local network. While it helps in troubleshooting connectivity and determining which devices are reachable, it does not verify the status of the router’s own interfaces or the IP addresses assigned to them.

In summary, show ip interface brief is the most appropriate command to verify a router interface’s status and IP configuration. It provides a quick, clear, and real-time overview of all interfaces, helping administrators ensure proper connectivity and troubleshoot issues efficiently.

Question 96:

Which protocol prevents routing loops in distance-vector protocols by limiting hop counts?

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

Answer: B

Explanation: 

RIP limits the maximum hop count to 15. Networks requiring more than 15 hops are considered unreachable, preventing indefinite loops.

Routing loops are a critical concern in network design because they can cause packets to circulate indefinitely, consuming bandwidth and potentially causing network congestion or failure. Distance-vector routing protocols, which determine the best path to a destination based on metrics such as hop count, are particularly susceptible to routing loops if preventive measures are not in place. Routing Information Protocol (RIP) is a distance-vector protocol that addresses this issue by implementing a maximum hop count limit. In RIP, the maximum number of hops allowed to reach a destination network is 15. Any network that requires more than 15 hops is considered unreachable. This limitation effectively prevents routing loops from persisting indefinitely because once the hop count reaches the maximum, the route is no longer propagateD)

Option A, OSPF (Open Shortest Path First), is a link-state protocol. OSPF prevents loops through a complete knowledge of the network topology. Each router maintains a link-state database and independently calculates the shortest path to each network using Dijkstra’s algorithm. While OSPF inherently avoids routing loops, it does not use hop count limitations as a mechanism for loop prevention.

Option C, EIGRP (Enhanced Interior Gateway Routing Protocol), is an advanced distance-vector protocol that combines distance-vector and link-state features. EIGRP prevents routing loops using a combination of the Diffusing Update Algorithm (DUAL), which ensures loop-free paths, and successor and feasible successor calculations. EIGRP does not rely on a maximum hop count to avoid loops.

Option D, BGP (Border Gateway Protocol), is an inter-domain routing protocol used between autonomous systems. BGP prevents routing loops through the AS-path attribute, which records the sequence of ASes a route has traverseD) BGP does not use hop count limits for loop prevention.

In summary, RIP is the protocol that prevents routing loops in distance-vector networks by limiting the maximum hop count to 15. This simple mechanism ensures that unreachable or excessively long paths are not propagated indefinitely, maintaining network stability while allowing small to medium-sized networks to function effectively.

Question 97: 

Which command displays which VLANs are allowed on a trunk port?

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

Answer: B

Explanation: 

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

Question 98: 

Which protocol dynamically maps IP addresses to MAC addresses for local delivery?

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

Answer: B

Explanation: 

ARP resolves IPv4 addresses to MAC addresses, enabling communication within the same Layer 2 segment.

Question 99: 

Which command on a Cisco router displays the interface IP addresses, operational status, and protocol state?

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

Answer: B

Explanation: 

show ip interface brief provides a concise summary of all interfaces, including IP addresses, interface status (up/down), and protocol status.

Question 100: 

A network engineer wants to prevent STP loops but still use redundant links. Which protocol should be implemented?

A) RIP
B) HSRP
C) STP
D) DHCP snooping

Answer: C

Explanation: 

Spanning Tree Protocol prevents Layer 2 loops by placing redundant links in a blocked state while maintaining at least one active path, allowing network redundancy without broadcast storms.