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Question 81. Which command is used to display detailed information about the IP configuration of a Cisco router interface?

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

Correct Answer: 2. show ip interface

Explanation :-

The show ip interface command displays detailed information about the IP configuration and operational status of router interfaces. It can show whether an interface has an IP address, whether IP processing is enabled, and various IP-related settings. This makes it useful when troubleshooting routing or connectivity problems. show vlan brief focuses on VLAN configuration, show mac address-table displays Layer 2 MAC address information, and show cdp neighbors provides information about directly connected Cisco devices. For more detailed interface statistics, show interfaces is commonly used.

Question 82. Which device operates primarily at Layer 2 of the OSI model and forwards frames based on MAC addresses?

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

Correct Answer: 4. Switch

Explanation :-

A network switch primarily operates at Layer 2, the Data Link layer, and uses MAC addresses to make forwarding decisions. It learns source MAC addresses from incoming frames and stores them in its MAC address table. When a destination MAC address is known, the switch forwards the frame through the appropriate port. Routers primarily operate at Layer 3 and use IP addresses for forwarding between networks. A DNS server resolves domain names to IP addresses, while a firewall may inspect and filter traffic according to configured security policies.

Question 83. Which IPv4 address belongs to the private 10.0.0.0/8 address range?

1. 10.25.40.8
2. 172.32.10.5
3. 192.169.1.10
4. 11.25.40.8

Correct Answer: 1. 10.25.40.8

Explanation :-

The IPv4 private address space defined by RFC 1918 includes 10.0.0.0/8, which covers addresses from 10.0.0.0 through 10.255.255.255. Therefore, 10.25.40.8 is a private IPv4 address. The other listed addresses do not belong to the RFC 1918 private ranges. The other private ranges are 172.16.0.0/12 and 192.168.0.0/16. Private addresses are commonly used inside organizations and normally require NAT or another mechanism when communicating with public IPv4 networks.

Question 84. Which protocol resolves a hostname such as www.example.com into an IP address?

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

Correct Answer: 3. DNS

Explanation :-

The Domain Name System, or DNS, translates human-readable domain names into IP addresses and can also provide other types of name-resolution information. When a user enters a hostname such as www.example.com, a DNS lookup can return the corresponding IPv4 or IPv6 address so the client can communicate with the destination. DHCP automatically provides network configuration such as IP addresses and default gateways. SNMP is used for network monitoring and management, while NTP synchronizes device clocks. DNS is therefore the protocol directly associated with hostname resolution.

Question 85. What is the primary function of a default gateway on an IPv4 host?

1. To assign the host’s MAC address
2. To provide local DNS caching
3. To forward traffic destined for remote networks
4. To resolve domain names

Correct Answer: 3. To forward traffic destined for remote networks

Explanation :-

A default gateway provides a host with a Layer 3 next hop for destinations outside the host’s local subnet. When the destination IP address is not part of the local network, the host sends the packet toward its configured default gateway, which is typically a router or Layer 3 switch. The gateway then determines how to forward the packet toward the remote network. Hosts do not normally send remote-network traffic directly to DNS servers or DHCP services. The default gateway is therefore essential for communication beyond the local subnet.

Question 86. Which protocol allows a Cisco device to automatically obtain an IPv4 address and other network configuration parameters?

1. ARP
2. DHCP
3. FTP
4. SSH

Correct Answer: 2. DHCP

Explanation :-

Dynamic Host Configuration Protocol, or DHCP, allows devices to automatically obtain network configuration information. A DHCP server can provide an IPv4 address, subnet mask, default gateway, DNS server information, and lease duration. This eliminates the need to manually configure each host. ARP resolves IPv4 addresses to MAC addresses on a local network. FTP transfers files, while SSH provides secure remote administrative access. DHCP is therefore the protocol used when a Cisco device or other network host needs to dynamically receive IPv4 configuration from a DHCP server.

Question 87. Which command saves the current running configuration to the startup configuration on a Cisco IOS device?

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

Correct Answer: 1. 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 is important because changes made to the running configuration can be lost if the device reloads before they are saved. The command effectively preserves the current configuration for use after a reboot. show running-config only displays the active configuration. erase startup-config removes the saved configuration, while reload restarts the device. Administrators commonly save configurations after making and verifying important changes.

Question 88. Which Layer 2 address is used to uniquely identify a network interface on an Ethernet network?

1. IPv4 address
2. TCP port
3. DNS name
4. MAC address

Correct Answer: 4. MAC address

Explanation :-

A Media Access Control, or MAC, address identifies a network interface at the Data Link layer. Ethernet switches use MAC addresses to determine where frames should be forwarded within a local network. An IPv4 address operates at Layer 3 and identifies a logical network endpoint, while a TCP port identifies an application or service at the transport layer. A DNS name is a human-readable identifier used for name resolution. MAC addresses are typically represented as hexadecimal values and are fundamental to Ethernet frame delivery on a local network.

Question 89. Which command displays the MAC address table on a Cisco switch?

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

Correct Answer: 2. show mac address-table

Explanation :-

The show mac address-table command displays MAC addresses learned by a Cisco switch and associates them with switch interfaces and VLAN information. This table is used by the switch to make Layer 2 forwarding decisions. It is particularly useful when troubleshooting situations where traffic is not reaching the expected switch port. show ip route displays Layer 3 routing information, show arp displays IPv4-to-MAC mappings, and show interfaces provides interface operational and statistical information. The MAC address table is therefore the appropriate source for verifying Layer 2 address learning.

Question 90. Which protocol is used by Cisco devices to discover directly connected neighboring Cisco devices?

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

Correct Answer: 4. CDP

Explanation :-

Cisco Discovery Protocol, or CDP, allows Cisco devices to discover information about directly connected neighboring Cisco equipment. It can provide details such as the neighboring device identifier, local and remote interfaces, platform, and capabilities. CDP operates at Layer 2 and is primarily used for network discovery and troubleshooting. DHCP is used for dynamic host configuration, TFTP provides lightweight file transfers, and HTTP is an application-layer protocol used for web-based communication. Administrators can use commands such as show cdp neighbors to inspect discovered Cisco neighbors.

Question 91. What is the purpose of a subnet mask in IPv4 addressing?

1. To identify the network and host portions of an IPv4 address
2. To encrypt IP packets
3. To assign a MAC address
4. To identify a TCP application

Correct Answer: 1. To identify the network and host portions of an IPv4 address

Explanation :-

An IPv4 subnet mask determines which bits of an IPv4 address represent the network portion and which represent the host portion. This allows devices to determine whether a destination is local or must be reached through a router. For example, a /24 mask corresponds to 255.255.255.0, leaving eight bits for host addressing. Subnet masks do not encrypt traffic, assign MAC addresses, or identify transport-layer applications. Correct subnet-mask configuration is essential for proper local communication and routing decisions within IPv4 networks.

Question 92. Which protocol provides secure command-line access to a remote network device?

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

Correct Answer: 3. SSH

Explanation :-

Secure Shell, or SSH, provides encrypted remote command-line access to network devices. It is commonly used by administrators to securely manage routers, switches, and other systems across a network. SSH encrypts authentication credentials and the management session, reducing the risk of credentials and administrative information being exposed. Telnet also provides remote command-line access but transmits information without encryption. TFTP and FTP are primarily file-transfer protocols. For secure remote network administration, SSH is therefore the preferred protocol among these choices.

Question 93. Which routing table entry has the highest priority when multiple routes match the same destination based on prefix length?

1. Route with the lowest bandwidth
2. Route learned most recently
3. Route with the highest interface number
4. Route with the longest prefix match

Correct Answer: 4. Route with the longest prefix match

Explanation :-

Routers use the longest prefix match principle when selecting among routing-table entries that match a destination IP address. The route with the most specific matching network prefix is preferred. For example, a /24 route is more specific than a /16 route when both match the destination. This process occurs before other route-selection considerations such as administrative distance and metric when comparing routes to the same destination. Interface numbering, bandwidth alone, or how recently a route was learned does not determine the longest-prefix selection.

Question 94. Which IPv6 address type is used for communication with multiple specific receivers that have joined a multicast group?

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

Correct Answer: 2. Multicast

Explanation :-

An IPv6 multicast address identifies a group of interfaces rather than a single destination. A packet sent to a multicast address can be delivered to multiple devices that have joined the corresponding multicast group. IPv6 multicast addresses use the FF00::/8 prefix. Global unicast addresses are normally used for unique routable destinations, link-local addresses are used for communication on the local link, and anycast addresses identify multiple interfaces while traffic is delivered to one appropriate member. Multicast is therefore the IPv6 address type designed for one-to-many group communication.

Question 95. Which command displays the current IPv4 routing table on a Cisco router?

1. show ip route
2. show ip interface brief
3. show vlan brief
4. show controllers

Correct Answer: 1. show ip route

Explanation :-

The show ip route command displays the IPv4 routing table on a Cisco router. The output can include connected, static, and dynamically learned routes, along with route codes, next-hop information, and outgoing interfaces. This command is frequently used when troubleshooting forwarding problems because it shows how the router currently knows to reach different networks. show ip interface brief provides concise interface status and addressing information, while show vlan brief focuses on VLANs. The routing table is the primary source for understanding IPv4 forwarding decisions.

Question 96. Which technology allows multiple VLANs to be carried over a single Ethernet link between network devices?

1. Port security
2. NAT
3. DHCP relay
4. 802.1Q trunking

Correct Answer: 4. 802.1Q trunking

Explanation :-

IEEE 802.1Q trunking allows multiple VLANs to traverse a single Ethernet link by adding VLAN identification information to Ethernet frames. A trunk link is commonly used between switches or between a switch and a router or Layer 3 device. This avoids the need for a separate physical link for every VLAN. Port security controls access to switch ports, NAT translates IP addresses, and DHCP relay forwards DHCP messages between different networks. Proper trunk configuration is important to ensure that the required VLANs are allowed and correctly identified across the link.

Question 97. Which Cisco IOS feature can restrict which MAC addresses are allowed to use a switch port?

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

Correct Answer: 3. Port security

Explanation :-

Switch port security allows administrators to control which MAC addresses can use a switch port. It can be configured to permit specific secure MAC addresses or dynamically learn addresses according to configured policies. Port security can also define an action when an unauthorized MAC address is detected, such as restricting or shutting down the port depending on the violation mode. NAT performs address translation, NTP synchronizes clocks, and CDP discovers neighboring Cisco devices. Port security is therefore the feature specifically designed to control Layer 2 device access through individual switch ports.

Question 98. Which command provides a concise summary of Cisco router interfaces, including IP addresses and up/down status?

1. show ip interface brief
2. show startup-config
3. show ip route
4. show access-lists

Correct Answer: 1. show ip interface brief

Explanation :-

The show ip interface brief command provides a concise overview of router interfaces. Its output typically includes the interface name, assigned IP address, administrative status, and line protocol status. This makes it particularly useful for quickly identifying interfaces that are down, administratively shut down, or missing expected IP addresses. show ip route displays routing information, show startup-config displays the saved configuration, and show access-lists displays configured ACL entries. Because of its compact output, show ip interface brief is one of the most useful initial commands for interface troubleshooting.

Question 99. Which IPv4 address is the loopback address commonly used to test the local TCP/IP stack?

1. 127.0.0.1
2. 169.254.1.1
3. 224.0.0.1
4. 255.255.255.255

Correct Answer: 1. 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 communication with another network device. Successful communication with 127.0.0.1 can help verify that the local networking stack is functioning. The 169.254.0.0/16 range is associated with IPv4 link-local addressing, 224.0.0.1 is an IPv4 multicast address, and 255.255.255.255 is the limited broadcast address. The loopback range is 127.0.0.0/8.

Question 100. Which command can be used to test reachability to a remote IPv4 destination from a Cisco device?

1. show vlan brief
2. ping
3. show mac address-table
4. copy startup-config running-config

Correct Answer: 2. ping

Explanation :-

The ping command tests IP connectivity between a Cisco device and a specified destination. It sends ICMP Echo Request messages and checks for corresponding Echo Reply messages. The results can help determine whether a destination is reachable and can provide basic information about packet loss and response time. show vlan brief displays VLAN information, show mac address-table displays Layer 2 MAC learning, and the copy command modifies configuration files. Ping is therefore a fundamental first-line troubleshooting tool for verifying basic Layer 3 reachability.