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Question 281. Which Cisco IOS command displays the status and IP address of all interfaces in a concise format?

1. show interfaces
2. show ip route
3. show arp
4. show ip interface brief

Correct Answer: 4. show ip interface brief

Explanation :-

The show ip interface brief command provides a concise summary of interfaces, including their assigned IPv4 addresses and operational status. It displays interface names, IP addresses, administrative status, and line protocol status. This makes it particularly useful for quickly identifying interfaces that are administratively down or whose line protocol is not operational. The show interfaces command provides much more detailed statistics, while show ip route displays the routing table and show arp displays IPv4-to-MAC mappings. Therefore, show ip interface brief is the appropriate command for a quick overview of interface and IPv4 status.

Question 282. Which IPv4 subnet mask corresponds to a /28 prefix?

1. 255.255.255.192
2. 255.255.255.240
3. 255.255.255.224
4. 255.255.255.248

Correct Answer: 2. 255.255.255.240

Explanation :-

A /28 IPv4 prefix contains 28 network bits and 4 host bits. The first three octets are completely dedicated to the network portion, while the fourth octet uses four network bits. Four network bits produce a decimal value of 240 in the final octet, resulting in the subnet mask 255.255.255.240. This subnet provides 16 total addresses per subnet, including the network and broadcast addresses. A /27 uses 255.255.255.224, while /29 uses 255.255.255.248. Therefore, 255.255.255.240 correctly corresponds to a /28 prefix.

Question 283. Which protocol is responsible for resolving domain names into IP addresses?

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

Correct Answer: 1. DNS

Explanation :-

The Domain Name System (DNS) resolves human-readable domain names into IP addresses that network devices can use for communication. For example, a client can use DNS to resolve a website hostname into an IPv4 or IPv6 address before establishing a connection. DNS commonly uses UDP port 53 for standard queries, although TCP can also be used in specific circumstances. DHCP provides network configuration, SNMP is used for monitoring and management, and NTP synchronizes clocks. Therefore, DNS is the protocol responsible for translating domain names into corresponding IP addresses.

Question 284. What happens when a router receives an IPv4 packet whose destination network is not present in its routing table and no default route exists?

1. The router broadcasts the packet to all interfaces
2. The router forwards the packet to the nearest switch
3. The router drops the packet
4. The router converts the packet into an ARP request

Correct Answer: 3. The router drops the packet

Explanation :-

If a router receives an IPv4 packet for a destination network that does not match any entry in its routing table and there is no default route, the router cannot determine where to forward the packet. It therefore discards the packet. Depending on the circumstances, the router may also generate an ICMP Destination Unreachable message toward the source. A router does not broadcast an unknown routed packet to all interfaces, forward it to a switch automatically, or use ARP to discover a route. ARP is used to resolve a next-hop IPv4 address to a MAC address after a forwarding decision has already been made.

Question 285. Which protocol prevents Layer 2 loops by placing redundant switch ports into a blocking or alternate state?

1. DHCP
2. STP
3. DNS
4. NAT

Correct Answer: 2. STP

Explanation :-

Spanning Tree Protocol (STP) prevents Layer 2 switching loops in networks with redundant paths. Without loop prevention, Ethernet frames can circulate continuously, causing broadcast storms, duplicate frames, and MAC address-table instability. STP calculates a loop-free logical topology and places selected redundant interfaces into a non-forwarding state while maintaining alternative paths for redundancy. If the active path fails, STP can allow an alternate path to become active. DHCP assigns network configuration, DNS resolves names, and NAT translates IP addresses. Therefore, STP is the protocol designed to prevent Layer 2 loops in switched Ethernet networks.

Question 286. Which command displays the MAC addresses learned by a Cisco switch?

1. show mac address-table
2. show ip route
3. show startup-config
4. show version

Correct Answer: 4. show mac address-table

Explanation :-

The show mac address-table command displays MAC addresses that a Cisco switch has learned or that have been statically configured. The output commonly includes VLAN information, MAC addresses, entry types, and associated interfaces. Switches learn source MAC addresses from incoming Ethernet frames and use this information to make Layer 2 forwarding decisions. The show ip route command displays routing information, show startup-config displays the saved configuration, and show version provides software and hardware details. Therefore, show mac address-table is the correct command for viewing MAC address-table entries.

Question 287. Which IPv6 address is used to identify the local host, similar to 127.0.0.1 in IPv4?

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

Correct Answer: 3. ::1

Explanation :-

The IPv6 address ::1 is the loopback address and identifies the local host. It serves a purpose similar to IPv4 address 127.0.0.1 and is used to test the local IPv6 protocol stack without sending traffic onto the physical network. FE80::/10 is the link-local unicast range, FF02::1 is a multicast address representing all IPv6 nodes on the local link, and 2001:DB8::/32 is reserved for documentation. Therefore, ::1 is the IPv6 loopback address used to communicate with the local system itself.

Question 288. Which Cisco protocol can automatically negotiate an EtherChannel between compatible devices?

1. CDP
2. VTP
3. LACP
4. ARP

Correct Answer: 3. LACP

Explanation :-

Link Aggregation Control Protocol (LACP) is an IEEE-standard protocol used to negotiate and maintain EtherChannel link aggregation between compatible devices. LACP allows multiple physical Ethernet links to operate as a single logical link, providing increased bandwidth and redundancy. Cisco devices may also support PAgP, a Cisco proprietary EtherChannel negotiation protocol. CDP discovers Cisco neighbors, VTP manages VLAN information in supported environments, and ARP resolves IPv4 addresses to MAC addresses. Therefore, LACP is the protocol among the choices that can negotiate an EtherChannel.

Question 289. Which command displays the IPv6 routing table on a Cisco router?

1. show ipv6 route
2. show ip route
3. show arp
4. show ipv6 interface brief

Correct Answer: 4. show ipv6 route

Explanation :-

The show ipv6 route command displays the IPv6 routing table on a Cisco router. It provides information about IPv6 network prefixes, route sources, administrative distances, metrics, next-hop information, and outgoing interfaces. The command is useful for verifying whether the router has a valid path toward an IPv6 destination. show ip route displays the IPv4 routing table, show arp is associated with IPv4 address resolution, and show ipv6 interface brief provides a concise IPv6 interface summary. Therefore, show ipv6 route is the appropriate command for examining IPv6 routes.

Question 290. Which device normally makes forwarding decisions based primarily on destination IP addresses?

1. Hub
2. Router
3. Layer 2 bridge
4. Repeater

Correct Answer: 1. Router

Explanation :-

A router makes Layer 3 forwarding decisions primarily using destination IP addresses. It examines the destination address in an IP packet, consults its routing table, selects the appropriate route, and forwards the packet toward the next hop or destination network. A traditional Layer 2 switch or bridge makes forwarding decisions using MAC addresses, while a hub and repeater operate by repeating signals rather than making IP routing decisions. Routers also separate broadcast domains and connect different IP networks. Therefore, a router is the device that normally forwards traffic based on destination IP addresses.

Question 291. Which Cisco command shows detailed information about a specific interface, including errors and packet counters?

1. show vlan brief
2. show ip route
3. show interfaces
4. show version

Correct Answer: 3. show interfaces

Explanation :-

The show interfaces command provides detailed operational information about Cisco interfaces. Depending on the interface, the output can include interface status, line protocol status, bandwidth, duplex and speed settings, packet counters, error statistics, collisions, encapsulation, and other operational details. This information is valuable when diagnosing physical or data-link problems. show vlan brief focuses on VLAN configuration, show ip route displays routing information, and show version provides system information. Therefore, show interfaces is the appropriate command when detailed interface statistics and error information are required.

Question 292. Which IPv4 address range is reserved for private Class A addressing?

1. 192.168.0.0/16
2. 169.254.0.0/16
3. 172.16.0.0/12
4. 10.0.0.0/8

Correct Answer: 4. 10.0.0.0/8

Explanation :-

The 10.0.0.0/8 range is reserved for private IPv4 addressing and corresponds to the traditional Class A private range. Private addresses are intended for internal networks and are not directly routable across the public Internet. The other RFC 1918 private ranges are 172.16.0.0/12 and 192.168.0.0/16. The 169.254.0.0/16 range is used for IPv4 link-local addressing rather than private RFC 1918 addressing. Therefore, 10.0.0.0/8 is the correct private Class A range.

Question 293. Which command can verify whether a Cisco switch has learned a particular MAC address?

1. show mac address-table
2. show ip interface brief
3. show version
4. show ip route

Correct Answer: 1. show mac address-table

Explanation :-

The show mac address-table command can be used to verify whether a Cisco switch has learned a particular MAC address. The command displays the switch’s Layer 2 forwarding database, including MAC addresses, VLAN assignments, and associated interfaces. An administrator can examine the output to determine which port and VLAN the switch associates with a device. show ip interface brief summarizes interface IP addressing and status, show version displays system information, and show ip route displays Layer 3 routes. Therefore, show mac address-table is the correct command for checking learned MAC addresses.

Question 294. Which protocol uses ICMP Echo Request and Echo Reply messages to test reachability?

1. FTP
2. Ping
3. DHCP
4. DNS

Correct Answer: 2. Ping

Explanation :-

The ping utility uses ICMP Echo Request and Echo Reply messages to test IP connectivity between devices. When a source sends an Echo Request to a destination and receives an Echo Reply, it provides evidence that the destination is reachable at the IP layer. Ping can also provide basic round-trip-time information and packet-loss observations. FTP transfers files, DHCP provides network configuration, and DNS resolves names. A successful ping does not guarantee that every application or service on the destination is functioning, but it is a fundamental tool for testing network-layer reachability. Therefore, ping is the correct choice.

Question 295. Which IPv6 address type is designed for communication within a local link and is not routed between links?

1. Global unicast
2. Multicast
3. Link-local unicast
4. Anycast

Correct Answer: 3. Link-local unicast

Explanation :-

IPv6 link-local unicast addresses are designed for communication between devices on the same local link. They use the FE80::/10 prefix and are not routed by IPv6 routers between different links. Link-local addressing is fundamental to IPv6 operations, including Neighbor Discovery and communication with directly connected IPv6 neighbors. Global unicast addresses are intended for broader routed communication, while multicast addresses identify groups of receivers and anycast addresses identify a set of interfaces where traffic is delivered to an appropriate member. Therefore, link-local unicast is the address type specifically intended for local-link communication.

Question 296. Which command displays a concise summary of IPv6 addresses and interface status?

1. show ipv6 interface brief
2. show ipv6 route
3. show ip interface brief
4. show interfaces

Correct Answer: 1. show ipv6 interface brief

Explanation :-

The show ipv6 interface brief command provides a concise summary of IPv6-enabled interfaces, including their IPv6 addresses and operational status. It is useful for quickly verifying IPv6 configuration and determining whether interfaces are administratively and operationally active. show ipv6 route displays the IPv6 routing table, show ip interface brief focuses on IPv4 addressing, and show interfaces provides more extensive interface statistics. When troubleshooting IPv6 configuration, this command can quickly reveal whether the expected IPv6 addresses are present on the appropriate interfaces. Therefore, show ipv6 interface brief is the correct command.

Question 297. What is the main function of a VLAN on a managed Ethernet switch?

1. Increase the physical cable length
2. Encrypt all Ethernet frames
3. Create separate logical broadcast domains
4. Replace the routing table

Correct Answer: 3. Create separate logical broadcast domains

Explanation :-

A Virtual LAN (VLAN) logically separates devices into different Layer 2 broadcast domains on a managed switch. Devices assigned to different VLANs are isolated at Layer 2, even when they are connected to the same physical switch. Communication between VLANs requires Layer 3 routing, such as through a router or multilayer switch. VLANs do not inherently encrypt Ethernet frames, increase cable length, or replace routing tables. They are commonly used to improve network segmentation, organization, and traffic management. Therefore, creating separate logical broadcast domains is the primary function of VLANs.

Question 298. Which protocol is commonly used to securely transfer files over an SSH connection?

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

Correct Answer: 2. SFTP

Explanation :-

Secure File Transfer Protocol (SFTP) provides file-transfer capabilities over an SSH connection. Because the SSH transport provides encryption and authentication, SFTP can protect file contents and credentials while they are transmitted. Traditional FTP does not inherently encrypt its communication, and TFTP provides simple file transfers without the same security features. HTTP is primarily used for web-based communication and is not the protocol specifically described here. Therefore, SFTP is the appropriate protocol for securely transferring files through an SSH-based connection.

Question 299. Which command saves the current running configuration so that it can be restored after a device reload?

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

Correct Answer: 4. copy running-config startup-config

Explanation :-

The copy running-config startup-config command saves the active configuration in RAM to the startup configuration stored in NVRAM. This allows the configuration to be loaded again when the device reloads. Configuration changes made only to the running configuration are lost after a reload if they have not been saved. show running-config displays the active configuration but does not save it, erase startup-config removes the saved configuration, and reload restarts the device. Therefore, copy running-config startup-config is the command used to preserve the current configuration across a reload.

Question 300. Which Cisco feature can inspect DHCP messages and help prevent unauthorized DHCP servers from providing addresses to clients?

1. DHCP snooping
2. Port mirroring
3. NAT
4. EtherChannel

Correct Answer: 1. DHCP snooping

Explanation :-

DHCP snooping is a Layer 2 security feature that allows a switch to inspect DHCP messages and distinguish trusted from untrusted interfaces. It can help prevent unauthorized DHCP servers from responding to clients by allowing DHCP server messages only through trusted ports. DHCP snooping can also build a binding database containing information such as client MAC addresses, IP addresses, VLANs, and interfaces. NAT translates IP addresses, EtherChannel aggregates physical links, and port mirroring copies traffic for monitoring. Therefore, DHCP snooping is the feature designed to help protect a switched network against rogue DHCP servers.