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Question 101. Which protocol is responsible for mapping an IPv4 address to a MAC address on a local network?

1. DNS
2. DHCP
3. ICMP
4. ARP

Correct Answer: 4. ARP

Explanation :-

Address Resolution Protocol (ARP) maps an IPv4 address to the corresponding MAC address on a local Ethernet network. When a device needs to send an IPv4 packet to another device on the same subnet, it can use ARP to discover the destination’s MAC address. The result is typically stored in an ARP cache for future use. DNS resolves hostnames to IP addresses, DHCP provides network configuration, and ICMP is used for control and diagnostic messaging. ARP operates between the network and data-link addressing functions and is essential for IPv4 communication across Ethernet networks.

Question 102. Which Cisco IOS command displays a brief summary of interface IP addresses and their operational status?

1. show interfaces
2. show ip interface brief
3. show running-config
4. show controllers

Correct Answer: 2. show ip interface brief

Explanation :-

The show ip interface brief command provides a concise summary of router or Layer 3 switch interfaces. Its output normally includes interface names, assigned IP addresses, administrative status, and line protocol status. It is especially useful during initial troubleshooting because an administrator can quickly identify interfaces that are administratively down or whose line protocol is down. show interfaces provides much more detailed operational information, while show running-config displays configuration information. show controllers provides hardware-related details. The brief interface command is therefore useful for quickly checking IP addressing and interface availability.

Question 103. What is the main purpose of a VLAN on a switched network?

1. To logically separate devices into different broadcast domains
2. To replace IP routing
3. To encrypt Ethernet frames
4. To increase the physical cable length

Correct Answer: 1. To logically separate devices into different broadcast domains

Explanation :-

A Virtual Local Area Network (VLAN) logically separates devices into distinct Layer 2 broadcast domains on a switch network. Devices in different VLANs are isolated at Layer 2 and generally require a Layer 3 routing function to communicate with each other. VLANs can help organize users, services, and network segments without requiring separate physical switches for every logical network. VLANs do not replace routing, encrypt Ethernet frames, or physically extend cable distances. Proper VLAN configuration is an important part of switched network design and traffic segmentation.

Question 104. Which type of Ethernet cable is traditionally used to connect a computer directly to a switch?

1. Rollover cable
2. Crossover cable
3. Straight-through cable
4. Serial cable

Correct Answer: 3. Straight-through cable

Explanation :-

A straight-through Ethernet cable has traditionally been used to connect different device types, such as a computer to a switch. Its transmit and receive wire pairs use the corresponding pin arrangement on both ends. Crossover cables were traditionally used for connecting similar device types, such as switch-to-switch or computer-to-computer connections, although modern devices often support Auto-MDIX and can automatically adapt to cable type. Rollover cables are commonly associated with console connections to Cisco equipment, while serial cables are used for certain WAN or legacy interfaces. The traditional PC-to-switch cable is therefore straight-through.

Question 105. Which routing protocol is a link-state routing protocol commonly used in enterprise IPv4 networks?

1. RIP
2. OSPF
3. ARP
4. DHCP

Correct Answer: 2. OSPF

Explanation :-

Open Shortest Path First (OSPF) is a link-state interior gateway routing protocol commonly used in enterprise networks. OSPF routers exchange link-state information and build a topology database, then use the Shortest Path First algorithm to calculate routes. RIP is a distance-vector routing protocol that uses hop count as its metric. ARP performs IPv4-to-MAC address resolution, while DHCP provides dynamic network configuration. OSPF supports scalable network designs and can use areas to organize larger routing domains. It is therefore the link-state routing protocol among the listed choices.

Question 106. Which command displays the current active configuration stored in RAM on a Cisco IOS device?

1. show startup-config
2. copy running-config startup-config
3. erase startup-config
4. show running-config

Correct Answer: 4. show running-config

Explanation :-

The show running-config command displays the configuration currently active in RAM on a Cisco IOS device. It is useful for reviewing commands that are currently affecting device operation and for verifying configuration changes before saving them. The startup configuration is stored separately and is used during boot. show startup-config displays that saved configuration, while copy running-config startup-config saves the active configuration to the startup configuration. Understanding the distinction between running and startup configurations is essential because unsaved changes can be lost after a reload.

Question 107. Which IPv4 address range is reserved for automatic link-local addressing when DHCP is unavailable?

1. 169.254.0.0/16
2. 10.0.0.0/8
3. 127.0.0.0/8
4. 224.0.0.0/4

Correct Answer: 1. 169.254.0.0/16

Explanation :-

The IPv4 range 169.254.0.0/16 is reserved for link-local addressing. A host may automatically assign itself an address from this range when it cannot obtain a normal IPv4 address through DHCP. Link-local addresses are intended for communication on the local network segment and are not normally routed between networks. The 10.0.0.0/8 range is private addressing, 127.0.0.0/8 is reserved for loopback functions, and 224.0.0.0/4 is used for IPv4 multicast. Therefore, 169.254.0.0/16 is the appropriate link-local range.

Question 108. Which switching method begins forwarding a frame after reading only the destination MAC address?

1. Store-and-forward
2. Fragment-free switching
3. Fast switching
4. Cut-through switching

Correct Answer: 4. Cut-through switching

Explanation :-

Cut-through switching begins forwarding a frame as soon as the switch has read enough of the frame to determine the destination MAC address. This can reduce forwarding latency because the switch does not wait for the entire frame to arrive before transmitting it. Store-and-forward switching receives the complete frame and performs a frame check before forwarding. Fragment-free switching waits beyond the initial portion of the frame before forwarding. Cut-through switching therefore emphasizes lower latency, while store-and-forward provides greater opportunity for frame validation before forwarding.

Question 109. Which command can be used to view neighboring devices discovered through CDP?

1. show ip route
2. show vlan brief
3. show cdp neighbors
4. show arp

Correct Answer: 3. show cdp neighbors

Explanation :-

The show cdp neighbors command displays information about Cisco devices discovered through Cisco Discovery Protocol. The output can identify neighboring devices and provide details such as the local interface, remote port, device ID, platform, and capabilities. This is useful when documenting a network or troubleshooting connectivity between directly connected Cisco devices. show ip route displays routing information, show vlan brief summarizes VLANs, and show arp displays IPv4-to-MAC address mappings. CDP neighbor information is therefore viewed with the dedicated CDP command.

Question 110. What is the primary purpose of Network Address Translation (NAT)?

1. To translate between different IP address spaces
2. To synchronize device clocks
3. To discover neighboring switches
4. To assign VLAN numbers

Correct Answer: 1. To translate between different IP address spaces

Explanation :-

Network Address Translation (NAT) translates IP addresses between different address spaces, commonly allowing private internal addresses to communicate with external networks using one or more public addresses. NAT can conserve public IPv4 addresses and can also hide internal addressing structures from directly appearing on external connections. It does not perform clock synchronization, which is handled by NTP, or neighbor discovery, which can be handled by CDP. VLAN configuration is a separate Layer 2 function. NAT is therefore primarily associated with translating source and/or destination IP addressing between network domains.

Question 111. Which ICMP message is commonly generated when a router cannot deliver an IP packet because the destination network is unreachable?

1. Echo Reply
2. Destination Unreachable
3. Router Advertisement
4. Redirect

Correct Answer: 2. Destination Unreachable

Explanation :-

ICMP Destination Unreachable messages notify a sender that an IP packet could not be delivered to its intended destination or service. Different codes can identify specific reasons, such as network unreachable, host unreachable, or port unreachable. ICMP Echo Reply is associated with successful ping responses. Router Advertisement is associated with IPv6 neighbor discovery functions, while ICMP Redirect can inform a host about a preferable next hop. Destination Unreachable is therefore the appropriate ICMP message when a router cannot reach the specified destination network.

Question 112. Which Cisco switch feature can help prevent unauthorized devices from connecting through a switch port?

1. NTP
2. Port security
3. DNS
4. CDP

Correct Answer: 2. Port security

Explanation :-

Cisco switch port security can restrict access to a switch port based on MAC addresses. An administrator can configure secure MAC addresses manually or allow the switch to learn addresses according to configured policies. When an unauthorized MAC address violates the configured policy, the switch can take a defined protective action depending on the violation mode. NTP synchronizes clocks, DNS resolves names, and CDP discovers neighboring Cisco devices. Port security is therefore specifically designed to provide a Layer 2 access-control mechanism at the switch-port level.

Question 113. Which IPv6 address prefix identifies global unicast addresses?

1. FF00::/8
2. FE80::/10
3. 2000::/3
4. FC00::/7

Correct Answer: 3. 2000::/3

Explanation :-

The IPv6 prefix 2000::/3 is allocated for global unicast addressing. Global unicast addresses are intended to provide globally unique IPv6 addresses that can be routed across IPv6 networks. FE80::/10 is used for link-local addresses, FC00::/7 is associated with unique local addresses, and FF00::/8 identifies multicast addresses. Understanding IPv6 address categories is important when configuring and troubleshooting IPv6 networks. Among the listed prefixes, 2000::/3 is the range associated with globally routable unicast addressing.

Question 114. What is the primary purpose of Access Control Lists (ACLs) on a Cisco router?

1. To synchronize network clocks
2. To assign IP addresses automatically
3. To learn MAC addresses
4. To permit or deny traffic according to defined criteria

Correct Answer: 4. To permit or deny traffic according to defined criteria

Explanation :-

Access Control Lists (ACLs) are used to control traffic by evaluating packets against configured criteria. Depending on the ACL type and configuration, criteria can include source and destination IP addresses, protocols, and ports. ACLs can be applied to interfaces or used by other Cisco features to determine whether traffic should be permitted or denied. ACLs do not automatically assign IP addresses, synchronize clocks, or learn MAC addresses. Proper ACL placement and ordering are important because entries are evaluated sequentially and an implicit deny applies at the end of an ACL.

Question 115. Which wireless technology standard is associated with Wi-Fi networks?

1. IEEE 802.11
2. IEEE 802.3
3. IEEE 802.1Q
4. IEEE 802.1D

Correct Answer: 1. IEEE 802.11

Explanation :-

IEEE 802.11 is the family of standards associated with wireless local area networking, commonly known as Wi-Fi. Different 802.11 amendments define capabilities involving wireless frequency bands, data rates, channel operation, security enhancements, and other characteristics. IEEE 802.3 is associated with Ethernet, IEEE 802.1Q defines VLAN tagging, and IEEE 802.1D historically defines important Layer 2 bridging and Spanning Tree concepts. Therefore, when identifying the IEEE family specifically associated with Wi-Fi communication, 802.11 is the correct choice.

Question 116. Which protocol provides centralized authentication, authorization, and accounting services for network access?

1. TFTP
2. RADIUS
3. ARP
4. CDP

Correct Answer: 2. RADIUS

Explanation :-

RADIUS, or Remote Authentication Dial-In User Service, provides centralized authentication, authorization, and accounting services for network access. It is commonly used with technologies such as network access control, wireless authentication, and remote access services. Centralizing these functions allows administrators to manage access policies and user credentials through a dedicated authentication infrastructure. TFTP is a lightweight file-transfer protocol, ARP maps IPv4 addresses to MAC addresses, and CDP discovers neighboring Cisco devices. RADIUS is therefore the protocol among these choices associated with centralized AAA services.

Question 117. Which command can be used to verify the status of an Ethernet interface and view errors and traffic statistics?

1. show vlan brief
2. show ip route
3. show interfaces
4. show startup-config

Correct Answer: 3. show interfaces

Explanation :-

The show interfaces command provides detailed operational information about network interfaces. Its output can include interface status, line protocol status, bandwidth, traffic statistics, packet counts, errors, collisions, and other interface-specific information. This makes it valuable when troubleshooting physical or data-link connectivity problems. show vlan brief focuses on VLAN information, show ip route displays routing information, and show startup-config displays the saved configuration. When an administrator needs detailed statistics and error counters for a particular Ethernet interface, show interfaces is an appropriate command.

Question 118. What happens when a switch receives a frame with an unknown destination MAC address?

1. It drops the frame immediately
2. It sends the frame only to the default gateway
3. It forwards the frame out all ports except the receiving port within the VLAN
4. It converts the frame into an IP packet

Correct Answer: 3. It forwards the frame out all ports except the receiving port within the VLAN

Explanation :-

When a Layer 2 switch receives a frame whose destination MAC address is not present in its MAC address table, the switch treats the frame as an unknown unicast. It floods the frame out appropriate ports within the same VLAN, excluding the port on which the frame was received. This allows the intended destination to receive the frame and respond, enabling the switch to learn its MAC address. The switch does not immediately send the frame to a default gateway or convert it into an IP packet. Once the destination MAC is learned, subsequent frames can be forwarded more selectively.

Question 119. Which protocol is commonly used to securely transfer files between a network device and a remote server?

1. TFTP
2. FTP
3. SFTP
4. ARP

Correct Answer: 3. SFTP

Explanation :-

SFTP, or SSH File Transfer Protocol, provides secure file transfer through an SSH-based connection. It protects authentication and file-transfer data using encryption and is suitable when secure file movement is required. TFTP is lightweight but does not provide strong authentication or encryption. Traditional FTP transfers files but does not inherently provide the same encrypted protection as SFTP. ARP is not a file-transfer protocol; it is used for IPv4-to-MAC address resolution. Therefore, SFTP is the appropriate choice when secure file transfer is required.

Question 120. Which networking device primarily forwards packets between different IP networks?

1. Router
2. Hub
3. Access point
4. Layer 2 bridge

Correct Answer: 1. Router

Explanation :-

A router is a Layer 3 networking device designed to forward packets between different IP networks. It examines destination IP addresses and uses its routing table to determine an appropriate next hop or outgoing interface. Routers can use connected, static, and dynamically learned routes to make forwarding decisions. A traditional hub repeats signals to connected ports, while a Layer 2 bridge forwards Ethernet frames using MAC addresses. A wireless access point primarily provides wireless connectivity to a network. Therefore, the router is the device specifically designed for inter-network IP packet forwarding.