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Question 241. Which Cisco IOS command displays the MAC address table learned by a switch?

1. show ip route
2. show interfaces status
3. show mac address-table
4. show arp

Correct Answer: 3. show mac address-table

Explanation :-

The show mac address-table command displays the MAC address table maintained by a Cisco switch. The output typically includes VLAN information, MAC addresses, the type of entry, and the interface through which each MAC address was learned. This command is useful for troubleshooting Layer 2 connectivity and verifying where a particular device is connected. show ip route displays the routing table, show interfaces status provides interface status information, and show arp displays ARP information. Therefore, show mac address-table is the appropriate command for viewing dynamically and statically learned MAC addresses on a switch.

Question 242. Which protocol is primarily used to automatically assign IP addresses and other network configuration parameters to hosts?

1. DHCP
2. DNS
3. SNMP
4. NTP

Correct Answer: 1. DHCP

Explanation :-

Dynamic Host Configuration Protocol (DHCP) automatically provides hosts with network configuration information. A DHCP server can assign an IP address, subnet mask, default gateway, and DNS server information to clients. This reduces the need to manually configure every device and helps prevent duplicate IP address assignments. DNS is responsible for resolving names to IP addresses, SNMP is used for network monitoring and management, and NTP synchronizes clocks. DHCP commonly uses UDP ports 67 and 68 for server and client communication. Therefore, DHCP is the protocol used to automatically provide hosts with essential IP configuration information.

Question 243. What is the primary purpose of a default gateway on an IPv4 host?

1. To translate domain names into IP addresses
2. To assign the host an IPv4 address
3. To provide physical connectivity to the switch
4. To forward traffic destined for networks outside the local subnet

Correct Answer: 4. To forward traffic destined for networks outside the local subnet

Explanation :-

A default gateway provides a host with a Layer 3 next-hop destination for traffic that is not intended for the local subnet. When an IPv4 host determines that a destination IP address belongs to another network, it sends the frame to the MAC address of its configured default gateway. The router then determines how to forward the packet toward the remote network. DNS resolves names, while DHCP can assign addresses and gateway information but does not itself forward user traffic. Therefore, the default gateway enables hosts to communicate with destinations outside their local IP network.

Question 244. Which Cisco IOS command can be used to view the current configuration stored in RAM?

1. show startup-config
2. show running-config
3. show flash:
4. show version

Correct Answer: 2. show running-config

Explanation :-

The show running-config command displays the active configuration currently running in RAM on a Cisco device. It includes configured interfaces, routing protocols, passwords, access lists, and other active settings. Changes made to the running configuration take effect immediately but are not automatically preserved after a reload. The copy running-config startup-config command can be used to save the current configuration to NVRAM. In contrast, show startup-config displays the saved configuration that will be loaded after a reload. Therefore, show running-config is the appropriate command for viewing the active configuration in RAM.

Question 245. Which IPv4 address is a valid private address?

1. 8.8.8.8
2. 172.32.10.5
3. 192.169.1.10
4. 172.20.15.10

Correct Answer: 4. 172.20.15.10

Explanation :-

The IPv4 private address ranges defined for private networks include 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16. The address 172.20.15.10 falls within 172.16.0.0 through 172.31.255.255, making it a valid private IPv4 address. Private addresses are commonly used inside organizations and are not directly routable across the public Internet. The addresses 8.8.8.8, 172.32.10.5, and 192.169.1.10 do not belong to the RFC 1918 private ranges. Therefore, 172.20.15.10 is the valid private address among the choices.

Question 246. Which network device primarily operates at Layer 2 and forwards frames based on MAC addresses?

1. Router
2. Firewall
3. Switch
4. DNS server

Correct Answer: 3. Switch

Explanation :-

A traditional Ethernet switch primarily operates at OSI Layer 2 and makes forwarding decisions using destination MAC addresses. The switch learns source MAC addresses from incoming frames and associates them with specific interfaces and VLANs. When a destination MAC address is known, the switch forwards the frame through the appropriate interface. Routers primarily make Layer 3 forwarding decisions using IP addresses, while DNS servers provide name-resolution services. Some modern switches also support Layer 3 routing, but their fundamental Ethernet switching function is based on MAC addresses. Therefore, a switch is the device described in the question.

Question 247. Which IPv6 address type is used for communication with all nodes on the local link?

1. FF02::1
2. FE80::1
3. 2001:DB8::1
4. ::1

Correct Answer: 1. FF02::1

Explanation :-

The IPv6 multicast address FF02::1 identifies all IPv6 nodes on the local link. IPv6 multicast addresses begin with FF, and the second hexadecimal portion identifies the scope. FF02 indicates link-local scope, meaning the multicast traffic remains on the local link. FE80::/10 is the IPv6 link-local unicast range, 2001:DB8::/32 is reserved for documentation, and ::1 is the IPv6 loopback address. Therefore, FF02::1 is the multicast address used to reach all IPv6 nodes on the local link.

Question 248. Which protocol is used by network devices to discover directly connected Cisco devices?

1. FTP
2. CDP
3. DHCP
4. HTTP

Correct Answer: 2. CDP

Explanation :-

Cisco Discovery Protocol (CDP) is a Cisco proprietary Layer 2 protocol used to discover information about directly connected Cisco devices. CDP can provide details such as the neighboring device’s hostname, platform, local and remote interfaces, and management IP address. It is particularly useful when troubleshooting or documenting a Cisco network. CDP operates independently of IP addressing because it functions at Layer 2. DHCP provides IP configuration, FTP transfers files, and HTTP provides web-based communication. Therefore, CDP is the protocol designed to identify and obtain information about directly connected Cisco devices.

Question 249. What is the main purpose of Spanning Tree Protocol (STP) in an Ethernet network?

1. To assign IP addresses automatically
2. To encrypt Ethernet frames
3. To prevent Layer 2 switching loops
4. To translate private addresses into public addresses

Correct Answer: 3. To prevent Layer 2 switching loops

Explanation :-

Spanning Tree Protocol (STP) prevents Layer 2 loops in switched Ethernet networks that contain redundant paths. Redundant links improve availability but can cause broadcast storms, duplicate frames, and MAC table instability if they are allowed to forward simultaneously. STP creates a loop-free logical topology by placing selected redundant interfaces into a blocking or alternate state while keeping necessary paths available. If an active path fails, STP can allow an alternate path to become active. STP does not assign IP addresses, perform encryption, or provide NAT. Therefore, preventing Layer 2 switching loops is its primary purpose.

Question 250. Which command displays a concise summary of IPv4 addresses and interface status on a Cisco router?

1. show ip interface brief
2. show mac address-table
3. show cdp neighbors
4. show arp

Correct Answer: 1. show ip interface brief

Explanation :-

The show ip interface brief command provides a concise summary of router interfaces and their IPv4 addressing and operational status. The output typically includes the interface name, IP address, administrative status, and line protocol status. It is commonly used as a quick troubleshooting command to determine whether interfaces are configured and operational. show mac address-table is primarily used on switches to display MAC addresses, show cdp neighbors displays directly connected Cisco neighbors, and show arp displays IPv4-to-MAC mappings. Therefore, show ip interface brief is the appropriate command for a quick interface and IPv4 status overview.

Question 251. Which subnet mask corresponds to an IPv4 prefix length of /26?

1. 255.255.255.0
2. 255.255.255.192
3. 255.255.255.224
4. 255.255.255.240

Correct Answer: 2. 255.255.255.192

Explanation :-

A /26 prefix contains 26 network bits and 6 host bits. In dotted-decimal notation, the first three octets are fully occupied by network bits, while the fourth octet contains two network bits followed by six host bits. Two network bits in the final octet produce the decimal value 192, resulting in the subnet mask 255.255.255.192. A /24 uses 255.255.255.0, /27 uses 255.255.255.224, and /28 uses 255.255.255.240. Therefore, 255.255.255.192 correctly represents the /26 prefix length.

Question 252. Which protocol provides secure remote CLI access to a Cisco device?

1. Telnet
2. TFTP
3. FTP
4. SSH

Correct Answer: 4. SSH

Explanation :-

Secure Shell (SSH) provides encrypted remote command-line access to network devices. SSH protects credentials and session data by encrypting the communication between the client and the Cisco device. Telnet also provides remote CLI access, but its traffic is transmitted without encryption, making it unsuitable when secure remote administration is required. TFTP is commonly used for simple file transfers, while FTP provides file transfer with different authentication and transport characteristics. Cisco devices can be configured to accept SSH connections through the VTY lines. Therefore, SSH is the appropriate protocol for secure remote CLI administration.

Question 253. Which routing principle causes a router to prefer a more specific route over a less specific route?

1. Longest prefix match
2. Round-robin forwarding
3. Broadcast forwarding
4. MAC address learning

Correct Answer: 1. Longest prefix match

Explanation :-

Routers use the longest prefix match principle when multiple routes match a packet’s destination IP address. The route with the longest matching network prefix is considered the most specific and is selected for forwarding. For example, a /24 route is more specific than a /16 route when both contain the destination address. This allows routers to make precise forwarding decisions when networks are represented by overlapping prefixes. MAC address learning is a Layer 2 switching function, while broadcast forwarding and round-robin forwarding do not define standard IPv4 route-selection behavior. Therefore, longest prefix match is the correct principle.

Question 254. Which protocol is commonly used to synchronize the clocks of network devices?

1. FTP
2. NTP
3. ARP
4. STP

Correct Answer: 3. NTP

Explanation :-

Network Time Protocol (NTP) is used to synchronize clocks across networked devices. Accurate time synchronization is important for logging, troubleshooting, security events, certificates, authentication systems, and correlation of events across multiple devices. Cisco devices can be configured to obtain time from an NTP server or another trusted time source. ARP resolves IPv4 addresses to MAC addresses, STP prevents Layer 2 loops, and FTP provides file-transfer functionality. NTP generally uses UDP port 123 for communication. Therefore, NTP is the protocol used to maintain synchronized time among network devices.

Question 255. What does an Ethernet switch do when it receives a frame with an unknown destination MAC address?

1. Drops the frame immediately
2. Sends the frame only to the default gateway
3. Converts the frame into an IP packet
4. Floods the frame out other ports in the same VLAN

Correct Answer: 4. Floods the frame out other ports in the same VLAN

Explanation :-

When a switch receives an Ethernet frame whose destination MAC address is not present in its MAC address table, it treats the frame as an unknown unicast. The switch floods the frame out all other forwarding interfaces within the same VLAN, except the interface on which the frame was received. When the destination device responds, the switch can learn its source MAC address and associate it with the appropriate interface. The switch does not automatically send the frame only to the default gateway or convert it into an IP packet. Therefore, flooding within the VLAN is the expected behavior.

Question 256. Which command saves the active Cisco IOS configuration to NVRAM?

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

Correct Answer: 3. copy running-config startup-config

Explanation :-

The copy running-config startup-config command saves the current active configuration from RAM to the startup configuration stored in NVRAM. This ensures that configuration changes are retained when the device is restarted. The running configuration contains the settings currently in use, while the startup configuration contains the settings loaded during boot. The reverse command, copy startup-config running-config, loads the saved configuration into the running configuration without rebooting. erase startup-config removes the saved configuration, and reload restarts the device. Therefore, copy running-config startup-config is used to preserve the active configuration across reloads.

Question 257. Which address is the IPv4 loopback address most commonly used to test the local TCP/IP stack?

1. 169.254.1.1
2. 127.0.0.1
3. 192.168.1.1
4. 255.255.255.255

Correct Answer: 2. 127.0.0.1

Explanation :-

The IPv4 address 127.0.0.1 is the commonly used loopback address for testing the local TCP/IP stack. Traffic sent to this address remains within the local host and does not require a physical network connection or transmission to another device. The entire 127.0.0.0/8 range is reserved for loopback purposes. Addresses in the 169.254.0.0/16 range are link-local addresses, 192.168.1.1 is commonly used as a private address, and 255.255.255.255 is the limited broadcast address. Therefore, 127.0.0.1 is the correct local loopback address.

Question 258. Which Cisco feature can restrict a switch port so that only specified or learned MAC addresses can use the port?

1. Port security
2. DHCP relay
3. NAT
4. NTP

Correct Answer: 1. Port security

Explanation :-

Switch port security can restrict which MAC addresses are permitted on a switch port. An administrator can configure specific secure MAC addresses or allow the switch to dynamically learn secure addresses. Port security can also define a violation action when an unauthorized MAC address is detected, such as restricting or shutting down the port depending on configuration. DHCP relay forwards DHCP messages between clients and servers across Layer 3 boundaries, NAT translates addresses between different address spaces, and NTP provides time synchronization. Therefore, port security is the Cisco feature designed to control which MAC addresses can use a switch port.

Question 259. Which IPv4 address represents the limited broadcast address?

1. 0.0.0.0
2. 224.0.0.1
3. 255.255.255.255
4. 127.0.0.1

Correct Answer: 3. 255.255.255.255

Explanation :-

The IPv4 address 255.255.255.255 is the limited broadcast address. A packet sent to this address is intended for all IPv4 hosts on the local network segment and is not routed by IPv4 routers. The address 0.0.0.0 has special meanings depending on context, including representing an unspecified address. 224.0.0.1 is an IPv4 multicast address used for all hosts on the local subnet, while 127.0.0.1 is the loopback address. Therefore, 255.255.255.255 is the correct limited broadcast address.

Question 260. Which command displays detailed information about the Cisco IOS version and hardware platform?

1. show vlan brief
2. show interfaces
3. show arp
4. show version

Correct Answer: 4. show version

Explanation :-

The show version command provides important information about a Cisco device, including the Cisco IOS software version, device model, processor information, memory, configuration register, and uptime. It is frequently used during troubleshooting and inventory checks to determine the software and hardware environment of a device. show vlan brief displays VLAN information, show interfaces provides detailed interface statistics and operational information, and show arp displays IPv4 address-to-MAC mappings. Therefore, show version is the appropriate command for viewing IOS version and hardware platform information.