200-301 Cisco Certified Network Associate (CCNA) Exam Dumps and Practice Test Questions Set 9 Q161-180

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Question 161: 

Which command verifies which VLANs a trunk interface is carrying?

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

Answer: B

Explanation: 

show interfaces trunk displays trunk interfaces, allowed VLANs, native VLAN, and encapsulation, useful for troubleshooting VLAN trunking issues.

The command used to verify which VLANs a trunk interface is carrying is show interfaces trunk. This command is particularly useful in network environments where multiple VLANs are configured and trunk links are deployed between switches or other network devices. By executing show interfaces trunk, a network administrator can see a detailed overview of all trunk ports on a switch, including the VLANs that are allowed on each trunk, the native VLAN for untagged traffic, and the encapsulation type used, such as 802.1Q or ISL. This information is essential for troubleshooting issues related to VLAN communication and ensuring that the correct VLANs are propagated across trunk links.

Option A, show vlan brief, provides a summary of all VLANs configured on a switch, including VLAN IDs, names, and the ports assigned to each VLAN. While it is helpful for understanding VLAN assignments on individual interfaces, it does not specifically indicate which VLANs are being carried over a trunk link. Therefore, it is not the most effective command for verifying trunk VLAN membership.

Option C, show running-config, displays the current active configuration of the switch, including interface configurations, VLAN assignments, and trunk settings. Although a trunk configuration can be found here, it requires manually inspecting each interface for trunk-related commands such as switchport mode trunk and switchport trunk allowed vlan. This makes it more time-consuming and prone to oversight compared to the direct and concise output of show interfaces trunk.

Option D, show spanning-tree, provides information about the spanning-tree protocol (STP) status on switch interfaces. It is useful for detecting loop prevention issues and the roles of interfaces in STP, but it does not provide information about VLANs being carried on trunk ports.

In summary, show interfaces trunk is the most appropriate command for quickly and accurately verifying which VLANs are being transmitted over a trunk interface, making it invaluable for VLAN troubleshooting and network maintenance.

Question 162: 

Which type of ACL can filter traffic based on source and 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 control over traffic by filtering source/destination IP, protocol, and port numbers, whereas standard ACLs filter only by source IP.

The type of ACL that can filter traffic based on source and destination IP addresses, protocol type, and port number is an extended ACL. Extended ACLs provide a high level of control over network traffic because they allow administrators to define very specific criteria for permitting or denying packets. This includes the ability to match on source and destination IP addresses, the transport layer protocol such as TCP, UDP, or ICMP, and even specific port numbers like HTTP (port 80) or FTP (port 21). This granular filtering makes extended ACLs essential for securing network segments, controlling traffic flow, and implementing access policies that go beyond simple source-based restrictions.

Option A, standard ACLs, are more limited in functionality. They only filter traffic based on the source IP address of packets. While standard ACLs are simpler to configure and useful for basic traffic control, they do not provide the capability to specify destination addresses, protocols, or port numbers. This limitation makes them less suitable for complex traffic management or security requirements where precise control is needeD)

Option C, named ACLs, are not a separate type of ACL in terms of functionality but rather a way to organize and identify ACLs with a name instead of a number. Named ACLs can be standard or extended, meaning the filtering capabilities depend on the type of ACL configured, not on the fact that it has a name. Therefore, while they offer easier management and readability, they do not inherently provide filtering based on multiple criteria unless they are defined as extendeD)

Option D, reflexive ACLs, are used to provide temporary, dynamic filtering by monitoring outbound traffic and creating temporary rules for corresponding inbound responses. Reflexive ACLs focus on session-based filtering rather than comprehensive control over source, destination, protocol, and port numbers. They are typically used to allow return traffic dynamically while maintaining a secure environment, but they do not offer the same level of static, detailed filtering as extended ACLs.

In conclusion, extended ACLs are the most suitable choice for filtering traffic with precise criteria, including source and destination IPs, protocols, and port numbers, providing network administrators with detailed traffic control and enhanced security.

Question 163: 

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

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

Answer: C

Explanation: 

Anycast addresses allow multiple devices to share the same IPv6 address, with routers delivering packets to the nearest device based on routing metrics.

The IPv6 address type used to identify multiple devices that share the same address, with packets delivered to the nearest device, is anycast. Anycast addressing is designed to allow several devices, often servers or network nodes, to share the same IPv6 address. When a packet is sent to an anycast address, routers determine the nearest device using routing metrics such as hop count or path cost and deliver the packet to that specific node. This makes anycast especially useful for services like DNS or content delivery networks, where multiple servers provide the same service and traffic should be routed to the most efficient or closest one. Anycast helps improve network performance, reduce latency, and provide redundancy.

Option A, unicast, is the most common type of IPv6 address. Unicast addresses are assigned to a single interface on a device, and packets sent to a unicast address are delivered specifically to that individual interface. While unicast ensures precise delivery to a single device, it does not allow multiple devices to share the same address, so it does not provide the routing flexibility or redundancy benefits of anycast.

Option B, multicast, is an IPv6 address type that delivers packets to all devices that are part of a defined multicast group. Multicast is useful for efficiently sending the same data to multiple devices simultaneously, such as streaming video or routing updates. However, multicast does not select the nearest device; instead, it delivers packets to all group members, making it unsuitable for scenarios where only the closest device should responD)

Option D, link-local addresses, are IPv6 addresses used for communication between nodes on the same local link or subnet. Every IPv6-enabled interface automatically has a link-local address. These addresses are crucial for routing protocols and local network functions, but they are not used to route packets across networks or to select the nearest device among multiple devices sharing an address.

In summary, anycast addresses provide a unique IPv6 functionality that allows multiple devices to share the same address while ensuring that packets are delivered to the nearest device based on routing metrics. This capability distinguishes anycast from unicast, multicast, and link-local addresses and makes it valuable for optimizing performance and redundancy in large networks.

Question 164: 

Which protocol dynamically resolves IP addresses to MAC addresses on a local network?

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

Answer: C

Explanation: 

ARP resolves IPv4 addresses to MAC addresses, allowing devices to communicate on a local network segment.

The protocol that dynamically resolves IP addresses to MAC addresses on a local network is ARP, or Address Resolution Protocol. ARP plays a crucial role in IPv4 networking by allowing devices to map the logical IP address of a host to its physical MAC address, which is necessary for data transmission on a local network segment. When a device wants to communicate with another device within the same subnet, it broadcasts an ARP request asking “Who has this IP address?” The device that owns the IP responds with its MAC address, enabling the sending device to encapsulate the data in the correct Layer 2 frame. Without ARP, devices would not be able to locate each other at the data link layer, making local network communication impossible.

Option A, DHCP, or Dynamic Host Configuration Protocol, is responsible for automatically assigning IP addresses and other network configuration details such as subnet masks, default gateways, and DNS servers to devices on a network. While DHCP simplifies network administration by ensuring devices receive valid IP addresses without manual configuration, it does not handle the mapping of IP addresses to MAC addresses for communication within the local network.

Option B, DNS, or Domain Name System, translates human-readable domain names into IP addresses. For example, DNS allows a user to access a website using a domain name instead of memorizing its IP address. DNS operates at a higher layer than ARP and does not deal with MAC addresses or direct communication on a local network segment.

Option D, ICMP, or Internet Control Message Protocol, is primarily used for network diagnostics and error reporting. Tools like ping and traceroute rely on ICMP to test connectivity and report network issues, but ICMP does not provide any mechanism for resolving IP addresses to MAC addresses.

In summary, ARP is the essential protocol for linking IPv4 addresses to their corresponding MAC addresses on a local network, enabling devices to communicate efficiently at the data link layer. While DHCP, DNS, and ICMP serve important network functions, they do not perform this critical address resolution task.

Question 165: 

Which command on a Cisco router displays all connected interfaces, their IP addresses, and protocol status?

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

Answer: C

Explanation: 

show ip interface brief provides a concise overview of interfaces, IP addresses, and operational/protocol status, essential for troubleshooting connectivity issues.

The command on a Cisco router that displays all connected interfaces, their IP addresses, and protocol status is show ip interface brief. This command provides a concise summary of each interface on the router, including the interface name, assigned IP address, operational status (up or down), and protocol status (whether the interface protocol is administratively up or down). It is one of the most commonly used commands for network troubleshooting because it allows administrators to quickly verify which interfaces are active and correctly configured, identify potential connectivity issues, and confirm that IP addressing has been applied properly. By offering a clear and organized view, show ip interface brief simplifies the process of monitoring and managing router interfaces.

Option A, show ip route, displays the router’s IP routing table, showing the network destinations known to the router, their next-hop addresses, and routing metrics. While this command is critical for understanding how traffic is routed through the network, it does not provide information about the operational or protocol status of individual interfaces, making it less useful for quickly assessing interface connectivity.

Option B, show running-config, shows the router’s active configuration, including interface settings, routing protocols, access control lists, and other configurations. Although it contains detailed information about IP addresses and interface configurations, administrators must manually examine each interface section, which is more time-consuming than using show ip interface brief.

Option D, show vlan brief, provides a summary of VLANs configured on a switch, including VLAN IDs, names, and assigned ports. This command is specific to switches and is used to verify VLAN configurations rather than the status of router interfaces. It does not display IP addresses or protocol status.

In conclusion, show ip interface brief is the most effective and efficient command for quickly checking all router interfaces, their IP addresses, and operational and protocol statuses, making it an essential tool for troubleshooting and network management.

Question 166: 

Which routing protocol supports hierarchical network design using areas and a link-state database?

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

Answer: B

Explanation: 

OSPF uses areas to segment large networks, reducing routing table size and limiting the scope of link-state advertisements for scalability.

The routing protocol that supports hierarchical network design using areas and a link-state database is OSPF, or Open Shortest Path First. OSPF is a link-state routing protocol that allows large networks to be organized into multiple areas, creating a hierarchical structure that improves scalability and efficiency. Each OSPF router maintains a link-state database that contains detailed information about the network topology within its areA) Using this database, OSPF calculates the shortest path to each network using the Dijkstra algorithm, ensuring optimal routing. By dividing a network into areas, OSPF reduces the size of routing tables, limits the scope of link-state advertisements, and decreases routing update traffic, which is especially important in large enterprise networks.

Option A, RIP, or Routing Information Protocol, is a distance-vector routing protocol that uses hop count as its metriC) RIP periodically broadcasts its entire routing table to neighbors, which can lead to inefficient use of bandwidth in larger networks. RIP does not support hierarchical network design or areas, and its scalability is limited due to a maximum hop count of 15. Consequently, it is unsuitable for very large or complex networks compared to OSPF.

Option C, EIGRP, or Enhanced Interior Gateway Routing Protocol, is an advanced distance-vector protocol that uses metrics like bandwidth, delay, and reliability to determine the best path. While EIGRP is more efficient than RIP and converges quickly, it does not use areas or a link-state database. Its hierarchical capabilities are limited, and it relies on a flat network structure rather than the area-based segmentation that OSPF provides.

Option D, BGP, or Border Gateway Protocol, is an exterior gateway protocol primarily used for routing between autonomous systems on the Internet. BGP focuses on policy-based routing and path selection rather than the hierarchical organization of internal networks. It does not maintain a link-state database or utilize areas for segmentation.

In conclusion, OSPF uniquely supports hierarchical network design through areas and link-state databases, making it ideal for large and scalable networks while providing efficient, optimal routing and reduced network overheaD)

Question 167: 

Which type of IPv4 address is reserved for private networks and cannot be routed on the Internet?

A) 8.8.8.8
B) 10.0.0.1
C) 192.168.1.1
D) Both B and C

Answer: D

Explanation: 

Private IPv4 address ranges 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.

The type of IPv4 address that is reserved for private networks and cannot be routed on the Internet includes addresses such as 10.0.0.1 and 192.168.1.1. These addresses belong to the private IP ranges defined by the Internet Assigned Numbers Authority (IANA), which are specifically set aside for use within local area networks (LANs) and other internal network environments. Private IPv4 addresses provide organizations with the flexibility to design their internal networks without consuming public IP addresses. Because these addresses are not routable on the public Internet, devices using them must rely on network address translation (NAT) if they need to communicate with external networks.

Option A, 8.8.8.8, is a public IP address maintained by Google for its public DNS service. This address is routable on the Internet and can be reached globally. It is not part of any private IP range, so it does not fall under the category of addresses reserved for internal network use.

Option B, 10.0.0.1, is part of the private IPv4 range 10.0.0.0/8. This entire block, from 10.0.0.0 to 10.255.255.255, is designated for private network use. Devices within a private network can use this range freely, but routers on the public Internet will not forward packets to these addresses, ensuring they remain isolated from external networks unless NAT is applieD)

Option C, 192.168.1.1, belongs to the 192.168.0.0/16 private address range. This range is commonly used for small networks, such as home or office environments. Like other private addresses, packets with a destination in this range cannot be routed on the public Internet directly, preserving address space and preventing conflicts with globally routable addresses.

Option D, both B and C, is correct because both 10.0.0.1 and 192.168.1.1 fall within the reserved private IP ranges. These addresses are essential for internal network design, allowing devices to communicate locally without consuming public IP addresses, while requiring NAT or similar mechanisms for external Internet access.

Question 168: 

Which protocol allows routers to exchange routing information between different autonomous systems?

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

Answer: C

Explanation: 

BGP is an inter-domain protocol used between autonomous systems on the Internet to exchange routing information and ensure global connectivity.

The protocol that allows routers to exchange routing information between different autonomous systems is BGP, or Border Gateway Protocol. BGP is classified as an inter-domain or exterior gateway protocol and is essential for the functioning of the global Internet. Unlike interior gateway protocols, which operate within a single autonomous system (AS), BGP enables routers in separate ASes to share routing information and determine the best paths for data to traverse across the Internet. BGP uses path vector mechanisms and considers policies, path attributes, and network reachability to make intelligent routing decisions, ensuring that traffic between ASes follows the most efficient or preferred paths. This protocol is critical for maintaining global connectivity and for managing how Internet service providers (ISPs) interconnect and exchange routing datA)

Option A, OSPF, or Open Shortest Path First, is an interior gateway protocol designed to operate within a single autonomous system. OSPF uses link-state routing and supports hierarchical network design through the use of areas. It is highly efficient for routing within large enterprise networks but cannot be used to exchange routing information between autonomous systems.

Option B, EIGRP, or Enhanced Interior Gateway Routing Protocol, is a Cisco-proprietary protocol that uses distance-vector and advanced metrics to determine optimal paths within an autonomous system. EIGRP is also limited to intra-domain routing and does not provide mechanisms for routing between different autonomous systems.

Option D, RIP, or Routing Information Protocol, is a distance-vector protocol that uses hop count as its metriC) Like OSPF and EIGRP, RIP is intended for routing within a single autonomous system and does not support inter-domain routing. Its simplicity and limitations make it unsuitable for large-scale Internet routing.

In conclusion, BGP is the only protocol among the options that operates between autonomous systems, enabling routers to exchange routing information across organizational and administrative boundaries. Its ability to handle inter-domain policies and global routing makes it indispensable for the Internet, distinguishing it from OSPF, EIGRP, and RIP, which are designed for routing within a single autonomous system.

Question 169: 

Which feature allows a switch to limit access to specific MAC addresses and take action when an unauthorized device connects?

A) Port Security
B) STP
C) DHCP Snooping
D) EtherChannel

Answer: A

Explanation: 

Port Security restricts which MAC addresses can connect to a switch port and can shut down, restrict, or log violations for unauthorized devices.

The feature that allows a switch to limit access to specific MAC addresses and take action when an unauthorized device connects is port security. Port security is a Layer 2 security mechanism that enhances network protection by restricting which devices can communicate through a particular switch port based on their MAC addresses. When configured, a switch can allow only a set number of MAC addresses on a port, and administrators can define specific actions if a violation occurs, such as shutting down the port, restricting traffic, or generating a log entry. This feature is especially useful in environments where unauthorized devices could pose security risks, such as corporate networks, schools, or public Wi-Fi deployments. By controlling access at the port level, port security helps prevent network breaches and unauthorized device connections.

Option B, STP or Spanning Tree Protocol, is a Layer 2 protocol that prevents switching loops in a network by creating a loop-free logical topology. While STP ensures stable network operation and avoids broadcast storms, it does not provide control over which devices can connect to a switch port or enforce MAC-based security.

Option C, DHCP Snooping, is a security feature that protects against unauthorized DHCP servers on a network. It monitors DHCP messages and ensures that only trusted ports can respond to DHCP requests. DHCP Snooping prevents rogue devices from assigning incorrect IP addresses, but it does not restrict access based on MAC addresses or take action when an unauthorized device connects to a port.

Option D, EtherChannel, is a method of combining multiple physical switch ports into a single logical link to increase bandwidth and provide redundancy. While EtherChannel improves network performance and link reliability, it does not offer security features to limit access based on device MAC addresses or handle unauthorized connections.

In conclusion, port security is the specific feature that enforces MAC-based access control on switch ports, providing protection against unauthorized devices while offering configurable responses to violations. STP, DHCP Snooping, and EtherChannel serve different purposes, such as loop prevention, DHCP security, and link aggregation, but they do not provide the direct access control capabilities offered by port security.

Question 170: 

Which command displays all active VLANs and their assigned ports on a Cisco switch?

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

Answer: C

Explanation: 

show vlan brief lists all VLANs, their operational status, and which ports are assigned to each VLAN.

The command that displays all active VLANs and their assigned ports on a Cisco switch is show vlan brief. This command provides a clear and concise summary of all VLANs configured on the switch, including their VLAN ID, name, status (active or inactive), and the ports associated with each VLAN. By using this command, network administrators can quickly verify VLAN configurations, ensure that ports are correctly assigned, and troubleshoot connectivity issues related to VLAN membership. It is an essential tool for managing switched networks, especially in environments with multiple VLANs where port assignments and operational status must be monitored regularly.

Option A, show mac-address-table, displays the MAC addresses that the switch has learned on its interfaces. This command is useful for identifying which devices are connected to which ports and for troubleshooting Layer 2 forwarding issues, but it does not provide a direct view of VLAN assignments. While it can indirectly help determine VLAN membership if combined with VLAN information, it is not as straightforward or comprehensive as show vlan brief.

Option B, show interfaces status, shows the operational status of each switch interface, including whether the port is up or down, its speed, duplex settings, and VLAN membership in some cases. Although it provides useful interface information, it does not give a complete summary of all VLANs on the switch or clearly list which ports belong to each VLAN.

Option D, show ip interface brief, is a command primarily used on routers and Layer 3 switches to display interface IP addresses, operational status, and protocol status. While it is valuable for checking IP configurations and interface health, it does not provide VLAN-specific information or port assignments at the Layer 2 level.

In conclusion, show vlan brief is the most appropriate command for obtaining a complete overview of VLANs and their associated ports. Unlike show mac-address-table, show interfaces status, or show ip interface brief, it is specifically designed to display VLAN configurations, making it a critical tool for network management and troubleshooting in switched environments.

Question 171: 

Which protocol is used to securely manage network devices over an IP network?

A) Telnet
B) SSH
C) FTP
D) HTTP

Answer: B

Explanation: 

SSH encrypts all management traffic, providing secure remote access to network devices, while Telnet sends credentials in plaintext.

The protocol used to securely manage network devices over an IP network is SSH, or Secure Shell. SSH provides encrypted communication between a network administrator and network devices such as routers, switches, or firewalls. By encrypting all management traffic, including usernames, passwords, and commands, SSH ensures that sensitive information is protected from eavesdropping or interception by unauthorized users. This makes SSH the preferred method for remote device management in modern networks, offering both confidentiality and authentication to prevent unauthorized access.

Option A, Telnet, is an older protocol that also allows remote management of network devices. However, Telnet transmits all data, including login credentials, in plaintext, making it highly vulnerable to interception and attacks. While Telnet is simple and widely supported, its lack of security makes it unsuitable for use over untrusted networks such as the Internet. As a result, SSH has largely replaced Telnet for secure network administration.

Option C, FTP, or File Transfer Protocol, is designed to transfer files between devices over a network. While FTP can move configuration files or software updates to network devices, it does not provide a secure method for interactive device management. Additionally, traditional FTP does not encrypt its traffic, meaning credentials and data can be exposed, though secure alternatives like SFTP (SSH File Transfer Protocol) do exist.

Option D, HTTP, is the protocol used for web-based communication and accessing web interfaces on devices. While some network devices provide web management through HTTP or HTTPS, HTTP itself does not encrypt traffic, leaving login credentials and commands vulnerable. HTTPS, which is HTTP over SSL/TLS, can provide secure web-based management, but it is not a protocol specifically designed for traditional command-line network device management like SSH.

In conclusion, SSH is the standard protocol for securely managing network devices over IP networks. Unlike Telnet, FTP, or HTTP, SSH encrypts all management traffic, preventing unauthorized access and ensuring that administrative sessions remain private and protected, making it essential for maintaining network security.

Question 172: 

Which command verifies the root bridge and port roles in a spanning-tree topology?

A) show interfaces status
B) show spanning-tree
C) show vlan brief
D) show ip route

Answer: B

Explanation: 

show spanning-tree displays root bridge information, port roles (root, designated, blocked), and STP state, helping identify loops and redundant paths.

The command that verifies the root bridge and port roles in a spanning-tree topology is show spanning-tree. This command provides a detailed view of the Spanning Tree Protocol (STP) configuration on a switch, including information about the root bridge, the bridge ID, and the priority of the switch. It also displays the role of each port, such as root, designated, or blocked, and the STP state of each port, whether forwarding, learning, or blocking. This information is essential for understanding how the STP algorithm has organized the network to prevent loops and ensure a loop-free topology. By using show spanning-tree, network administrators can identify the root bridge, verify that the topology is functioning correctly, and troubleshoot issues related to redundant links or misconfigurations.

Option A, show interfaces status, provides the operational status of each switch interface, including whether it is up or down, its speed, duplex settings, and VLAN assignment. While it is useful for checking port status and connectivity, it does not provide any information about STP, the root bridge, or port roles, making it insufficient for analyzing the spanning-tree topology.

Option C, show vlan brief, displays all VLANs configured on the switch, their status, and the ports assigned to each VLAN. This command is helpful for managing VLAN configurations but does not show the root bridge, port roles, or STP states. It is unrelated to loop prevention and spanning-tree analysis.

Option D, show ip route, shows the routing table on a Layer 3 device, including network destinations, next-hop addresses, and routing metrics. This command is focused on IP routing rather than Layer 2 loop prevention, VLAN port assignments, or spanning-tree operations.

In conclusion, show spanning-tree is the correct command for verifying the root bridge, port roles, and STP states in a spanning-tree topology. Unlike show interfaces status, show vlan brief, or show ip route, it provides comprehensive information about loop prevention, redundant paths, and the overall Layer 2 topology, making it an essential tool for network troubleshooting and management.

Question 173: 

Which type of NAT allows multiple private IP addresses to share a single public IP using unique port numbers?

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

Answer: C

Explanation: 

PAT (Port Address Translation) enables multiple private IPs to share one public IP with different TCP/UDP port numbers, also called NAT overloaD)

The type of NAT that allows multiple private IP addresses to share a single public IP address using unique port numbers is PAT, or Port Address Translation. PAT is also commonly referred to as NAT overload because it enables many devices within a private network to access external networks, such as the Internet, using a single public IP address. It works by translating the private IP addresses and their associated source port numbers into the public IP address with unique port numbers for each session. This allows the router or firewall to distinguish between multiple connections simultaneously, ensuring that return traffic is correctly routed back to the originating private IP device. PAT is widely used in home networks, small offices, and large enterprise environments because it conserves public IP addresses while allowing multiple devices to communicate externally.

Option A, static NAT, maps a single private IP address to a specific public IP address. This type of NAT is one-to-one, meaning each private IP has a dedicated public IP. While static NAT ensures predictable addressing for certain devices like servers, it does not allow multiple private addresses to share a single public IP, so it is not suitable for scenarios where many internal devices need simultaneous Internet access.

Option B, dynamic NAT, maps private IP addresses to a pool of available public IP addresses on a first-come, first-served basis. Each internal device receives a public IP temporarily, but the number of simultaneous connections is limited by the size of the public IP pool. Dynamic NAT cannot allow multiple private IPs to share a single public IP using port numbers, which limits its scalability compared to PAT.

Option D, dual NAT, refers to a NAT scenario where both source and destination IP addresses are translated, typically used for complex routing or overlapping address spaces. While dual NAT handles advanced translation requirements, it does not specifically address the need for multiple private IPs to share a single public IP with unique port numbers.

In conclusion, PAT is the NAT solution that enables many private IP addresses to access external networks simultaneously using one public IP, distinguishing each connection by unique port numbers. Static NAT, dynamic NAT, and dual NAT serve different purposes but do not provide this port-based sharing capability.

Question 174: 

Which command displays the routing table on a Cisco router?

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

Answer: A

Explanation: 

show ip route displays all known routes, including directly connected, static, and dynamic routes, along with next hops and exit interfaces.

The command that displays the routing table on a Cisco router is show ip route. This command provides a comprehensive view of all known routes within the router, including directly connected networks, static routes configured manually by the administrator, and dynamic routes learned from routing protocols such as OSPF, EIGRP, or BGP. The routing table output includes key details such as the destination network, the subnet mask, the next-hop IP address, the exit interface, and the administrative distance or metric of each route. By using show ip route, network administrators can verify how traffic will be forwarded, troubleshoot routing issues, and ensure that all necessary networks are reachable. This command is essential for understanding the router’s perspective of the network topology and making informed decisions when configuring or adjusting routing policies.

Option B, show running-config, displays the router’s active configuration, including interface settings, routing protocol configurations, access control lists, and other parameters. While show running-config contains information about routes and protocols, it requires careful manual inspection to determine which routes are active or preferreD) It does not provide a summarized, real-time view of the routing table like show ip route, making it less efficient for quickly analyzing the router’s routing decisions.

Option C, show interfaces, provides detailed information about the status of each router interface, including whether it is up or down, its IP address, line protocol, bandwidth, and error statistics. Although this command is helpful for diagnosing interface connectivity issues, it does not provide a list of networks or next-hop information, so it cannot be used to view the routing table.

Option D, show vlan brief, is primarily used on switches to display VLAN configurations, operational status, and port assignments. It is unrelated to routing tables and does not provide any information about IP routes or packet forwarding decisions.

In conclusion, show ip route is the definitive command for viewing all active routes on a Cisco router. Unlike show running-config, show interfaces, or show vlan brief, it gives a direct and complete view of routing information, including static, dynamic, and connected routes, along with next-hop addresses and exit interfaces, making it indispensable for routing verification and troubleshooting.

Question 175: 

Which protocol is used to send error messages such as “destination unreachable” or “TTL exceeded”?

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

Answer: B

Explanation: 

ICMP communicates errors and operational messages for IP networks, including unreachable hosts, network congestion, and connectivity tests (ping).

The protocol used to send error messages such as “destination unreachable” or “TTL exceeded” is ICMP, or Internet Control Message Protocol. ICMP operates at the network layer and is an integral part of the IP protocol suite, providing diagnostic and error-reporting functions for IP networks. When a router or host encounters an issue delivering a packet, such as when the destination network is unreachable, the time-to-live (TTL) of a packet expires, or congestion prevents delivery, ICMP generates messages to notify the source device of the problem. These messages allow network administrators and devices to detect connectivity issues, verify paths, and troubleshoot network failures. Tools like ping and traceroute rely on ICMP to test reachability and measure the route that packets take across a network.

Option A, ARP or Address Resolution Protocol, is used to map IPv4 addresses to MAC addresses on a local network. ARP enables devices to find the physical address of a host on the same subnet but does not provide error reporting or communicate operational messages between devices. Therefore, it cannot send messages such as “destination unreachable” or “TTL exceedeD)”

Option C, DNS or Domain Name System, translates human-readable domain names into IP addresses, allowing users to access websites and services using easy-to-remember names. DNS is focused on name resolution and does not handle network error reporting or diagnostics.

Option D, DHCP or Dynamic Host Configuration Protocol, dynamically assigns IP addresses and other network configuration details to devices on a network. While DHCP facilitates network connectivity, it does not report delivery errors or provide operational messages between hosts and routers.

In summary, ICMP is the protocol responsible for sending error messages and operational notifications in IP networks. Unlike ARP, DNS, or DHCP, ICMP provides critical feedback about network issues, allowing devices to detect unreachable destinations, expired TTLs, or congestion, making it essential for network troubleshooting and connectivity testing.

Question 176: 

Which type of ACL filters traffic only by source IP address?

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

Answer: A

Explanation: 

Standard ACLs filter traffic based solely on the source IP address, while extended ACLs provide filtering by source, destination, protocol, and port number.

Question 177:

Which protocol is used to translate domain names into IP addresses?

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

Answer: B

Explanation: 

DNS resolves hostnames into IP addresses, enabling users to access network resources using human-readable names.

The protocol used to translate domain names into IP addresses is DNS, or Domain Name System. DNS is a critical component of the Internet and IP-based networks, allowing users to access websites and network services using human-readable domain names instead of memorizing numeric IP addresses. When a user types a domain name, such as www.example.com, into a browser, the DNS protocol queries a DNS server to find the corresponding IP address. Once resolved, the device can establish a connection to the destination server using the IP address. This process greatly simplifies network communication and is essential for the usability of the Internet.

Option A, DHCP, or Dynamic Host Configuration Protocol, is used to automatically assign IP addresses, subnet masks, default gateways, and other network configuration information to devices on a network. While DHCP ensures that devices receive valid IP configurations and can communicate within the network, it does not resolve domain names into IP addresses. DHCP focuses on providing connectivity rather than name resolution.

Option C, ICMP, or Internet Control Message Protocol, is used for network diagnostics and error reporting. ICMP communicates messages such as “destination unreachable” or “TTL exceeded” to indicate network issues and assist in troubleshooting. Although ICMP is vital for identifying network problems, it does not perform any function related to translating hostnames into IP addresses.

Option D, ARP, or Address Resolution Protocol, is used to map IPv4 addresses to MAC addresses on a local network. ARP allows devices to locate each other at the data link layer within the same subnet but does not provide name resolution services.

In conclusion, DNS is the protocol specifically designed to resolve human-readable hostnames into IP addresses, enabling users to access websites and network resources efficiently. Unlike DHCP, ICMP, or ARP, DNS directly addresses the challenge of translating names into addresses, making it indispensable for Internet navigation and network usability.

Question 178: 

Which command displays all VLAN trunks on a Cisco switch and their status?

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

Answer: B

Explanation: 

show interfaces trunk displays all trunk interfaces, allowed VLANs, native VLAN, and encapsulation type, helping troubleshoot VLAN communication.

Question 179: 

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

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

Answer: B

Explanation:

IPv6 link-local addresses (FE80::/10) are automatically assigned and used for communication between devices on the same link, required for routing protocols and neighbor discovery.

Question 180: 

Which protocol allows monitoring of network devices and generating alerts for abnormal events?

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

Answer: B

Explanation: 

SNMP enables monitoring of network devices, collection of statistics, and alerting administrators when abnormal conditions or failures occur.