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Question 21. Which command displays the MAC address table on a Cisco switch?

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

Correct Answer: 4. show mac address-table

Explanation :-

The show mac address-table command displays MAC addresses that a Cisco switch has learned and the interfaces or VLANs associated with those addresses. Switches use this information to make Layer 2 forwarding decisions. The command is useful when troubleshooting connectivity, verifying MAC learning, or determining which switch port is associated with a particular device. show ip route displays Layer 3 routing information, show interfaces provides interface statistics and configuration details, and show vlan brief summarizes VLAN membership. Exam questions commonly test the distinction between MAC address tables used by switches and routing tables used by routers.

Question 22. Which device typically separates broadcast domains by default?

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

Correct Answer: 1. Router

Explanation :-

A router separates broadcast domains because Layer 2 broadcasts are not normally forwarded from one routed interface to another. Each router interface represents a separate Layer 3 network and therefore a separate broadcast domain. Switches can also create multiple broadcast domains when VLANs are configured, but a basic Layer 2 switch forwards broadcasts within the same VLAN. A hub and repeater operate at the Physical layer and do not provide Layer 3 broadcast-domain separation. Understanding broadcast-domain boundaries is important when designing networks and determining where routing or VLAN configuration is required.

Question 23. Which IPv4 address represents the loopback address of a host?

1. 169.254.1.10
2. 192.168.1.1
3. 127.0.0.1
4. 224.0.0.1

Correct Answer: 3. 127.0.0.1

Explanation :-

The IPv4 loopback range is 127.0.0.0/8, with 127.0.0.1 commonly used as the loopback address for the local host. Traffic sent to a loopback address is processed by the local networking stack rather than being sent onto the physical network. This makes loopback addresses useful for testing local TCP/IP functionality and applications. The 169.254.0.0/16 range is associated with link-local addressing, 192.168.0.0/16 is a private address range, and 224.0.0.0/4 is used for IPv4 multicast. Recognizing special IPv4 address ranges is important for troubleshooting and configuration.

Question 24. Which routing protocol is classified as a link-state interior gateway protocol?

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

Correct Answer: 2. OSPF

Explanation :-

Open Shortest Path First (OSPF) is a link-state interior gateway protocol used to exchange routing information within an autonomous system. OSPF routers build a link-state database and use the Shortest Path First algorithm to calculate routes. RIP is a distance-vector routing protocol, while FTP and ARP are not routing protocols. OSPF supports hierarchical network design through areas and can provide efficient routing in larger networks. Understanding routing-protocol characteristics helps administrators determine how routers learn routes and how routing decisions are calculated.

Question 25. What is the main function of a subnet mask?

1. To identify the network and host portions of an IPv4 address
2. To encrypt IPv4 traffic
3. To identify a device’s MAC address
4. To assign a DNS server

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

Explanation :-

A subnet mask identifies which bits of an IPv4 address represent the network portion and which bits represent the host portion. This information allows a host to determine whether a destination is on the local subnet or must be reached through a router. For example, a /24 prefix uses the first 24 bits for the network portion and leaves 8 bits for host addressing. Subnet masks do not encrypt traffic, identify MAC addresses, or directly assign DNS servers. Correct subnet-mask configuration is essential because an incorrect mask can cause local and remote traffic to be handled incorrectly.

Question 26. Which Cisco IOS command saves the active configuration so that it can be used after a device reload?

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

Correct Answer: 2. copy running-config startup-config

Explanation :-

The copy running-config startup-config command saves the currently active configuration from RAM to the startup configuration stored in NVRAM. This allows the configuration to be loaded when the Cisco device reloads. Changes made only to the running configuration can be lost if the device is restarted before they are saved. The show startup-config command displays the saved configuration but does not save changes. erase startup-config removes the saved configuration, while reload restarts the device. Administrators should understand the distinction between running and startup configurations when making changes to Cisco devices.

Question 27. Which protocol automatically assigns IPv6 addresses and other configuration information using a DHCPv6 server?

1. DHCPv6
2. ARP
3. FTP
4. SNMP

Correct Answer: 1. DHCPv6

Explanation :-

DHCPv6 provides IPv6 hosts with configuration information from a DHCPv6 server. Depending on the deployment, it can provide addressing information and other parameters such as DNS-related configuration. IPv6 also supports Stateless Address Autoconfiguration (SLAAC), which can allow hosts to construct addresses based on router advertisements without requiring a DHCPv6 server for address assignment. ARP is an IPv4 protocol; IPv6 uses Neighbor Discovery instead. FTP provides file transfer and SNMP is used for network management. Understanding DHCPv6 and SLAAC is important when designing IPv6 addressing and configuration strategies.

Question 28. Which Ethernet feature allows a switch interface to carry traffic for multiple VLANs?

1. Access mode
2. Port security
3. Trunking
4. MAC filtering

Correct Answer: 3. Trunking

Explanation :-

A trunk link carries traffic belonging to multiple VLANs across a single physical connection. VLAN identification is maintained using a trunking mechanism such as IEEE 802.1Q tagging. Trunk links are commonly used between switches and between switches and devices such as routers or multilayer switches that need access to multiple VLANs. An access port normally carries traffic for one VLAN. Port security and MAC filtering provide security or access-control functions but do not perform VLAN trunking. Proper trunk configuration is important for maintaining VLAN connectivity across multiple network devices.

Question 29. Which protocol is used by IPv6 Neighbor Discovery to discover neighboring devices and routers?

1. ICMPv6
2. FTP
3. TCP
4. SMTP

Correct Answer: 1. ICMPv6

Explanation :-

IPv6 Neighbor Discovery uses ICMPv6 messages to perform functions such as discovering neighboring nodes, discovering routers, resolving link-layer addresses, and determining address reachability. It replaces several functions traditionally associated with ARP in IPv4. Neighbor Solicitation and Neighbor Advertisement messages are among the ICMPv6 messages used for neighbor-related operations. FTP is a file-transfer protocol, TCP provides reliable transport, and SMTP is used for email transfer. Understanding ICMPv6 is essential when troubleshooting IPv6 because it supports several fundamental control and configuration functions.

Question 30. Which wireless security protocol provides stronger protection than the original WEP standard?

1. HTTP
2. WPA2
3. FTP
4. Telnet

Correct Answer: 2. WPA2

Explanation :-

WPA2 provides significantly stronger wireless security than the older WEP standard and commonly uses AES-based encryption with CCMP. WPA2 has been widely deployed in wireless networks for protecting data transmitted between wireless clients and access points. WEP has well-known security weaknesses and should not be relied upon for modern secure deployments. HTTP and FTP are application-layer protocols, while Telnet provides remote terminal access and does not provide wireless encryption. Wireless security configuration should also consider authentication methods, strong credentials, network segmentation, and the capabilities of the wireless infrastructure.

Question 31. What is the purpose of the default route in a router’s routing table?

1. To identify only directly connected hosts
2. To provide a route for destinations that do not match a more specific route
3. To block all unknown destinations
4. To assign IP addresses to interfaces

Correct Answer: 2. To provide a route for destinations that do not match a more specific route

Explanation :-

A default route provides a forwarding path for packets when the routing table does not contain a more specific matching route. In IPv4, the default route is commonly represented as 0.0.0.0/0, while IPv6 uses ::/0. The router forwards matching traffic toward the configured next hop or exit interface. A default route does not assign IP addresses or identify only directly connected hosts. It is especially useful on edge routers and stub networks where unknown external destinations can be sent toward an upstream provider or gateway.

Question 32. Which command displays the IPv4 routing table on a Cisco IOS router?

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

Correct Answer: 3. show ip route

Explanation :-

The show ip route command displays the IPv4 routing table maintained by a Cisco IOS router or Layer 3 switch. The output can include connected routes, static routes, dynamically learned routes, and a default route. Routing-table entries contain information that helps the device determine where packets should be forwarded. show arp displays IP-to-MAC mappings, show vlan brief summarizes VLANs, and show mac address-table displays Layer 2 MAC learning information. During routing troubleshooting, show ip route is an essential command for verifying whether the device has a usable route toward a destination.

Question 33. 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 in every VLAN
4. It floods the frame out appropriate ports within the same VLAN, excluding the incoming port

Correct Answer: 4. It floods the frame out appropriate ports within the same VLAN, excluding the incoming port

Explanation :-

When a switch receives a frame whose destination MAC address is not present in its MAC address table, it treats the destination as an unknown unicast. The switch floods the frame out other active ports belonging to the same VLAN, excluding the interface on which the frame arrived. If the destination device responds, the switch can learn its source MAC address and associate it with the receiving port. The switch does not flood the frame across every VLAN because VLANs create separate Layer 2 broadcast domains. This behavior is fundamental to understanding Ethernet switching and MAC address learning.

Question 34. Which command can be used to test DNS name resolution from a Cisco IOS device?

1. nslookup
2. ping
3. traceroute
4. show vlan

Correct Answer: 2. ping

Explanation :-

On Cisco IOS, the ping command can be used with a hostname to test both name resolution and connectivity when DNS lookup is configured and available. If a hostname resolves successfully, the device can display or use the corresponding IP address for the ping operation. traceroute is primarily used to identify the Layer 3 path toward a destination, while show vlan provides VLAN information. nslookup is commonly associated with Windows and other operating systems rather than being the primary Cisco IOS command for this task. DNS troubleshooting should distinguish name-resolution problems from actual IP connectivity problems.

Question 35. Which IPv4 address range is reserved for link-local addressing when a host cannot obtain an address through DHCP?

1. 10.0.0.0/8
2. 172.16.0.0/12
3. 169.254.0.0/16
4. 224.0.0.0/4

Correct Answer: 3. 169.254.0.0/16

Explanation :-

The IPv4 link-local address range is 169.254.0.0/16. A host may automatically select an address from this range when it cannot obtain an IPv4 address through normal configuration mechanisms such as DHCP. Link-local addresses are intended for communication on the local network segment and are not normally routed across routers. The 10.0.0.0/8 and 172.16.0.0/12 ranges are private IPv4 address spaces, while 224.0.0.0/4 is reserved for multicast. Seeing a 169.254.x.x address can therefore provide a useful troubleshooting clue when investigating DHCP or local network connectivity.

Question 36. Which protocol is commonly used to synchronize the clocks of network devices?

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

Correct Answer: 1. NTP

Explanation :-

Network Time Protocol (NTP) is used to synchronize clocks across networked devices. Accurate time is important for logging, troubleshooting, authentication, certificate validation, event correlation, and security monitoring. Network devices can synchronize with configured NTP servers and maintain a consistent time reference. DHCP can provide configuration information, ARP resolves IPv4 addresses to MAC addresses, and ICMP provides network-control and diagnostic messages. Consistent timestamps are especially useful when administrators compare events across multiple routers, switches, firewalls, and servers during troubleshooting or security investigations.

Question 37. Which switching method begins forwarding a frame after reading only enough of the frame to determine the destination MAC address?

1. Store-and-forward
2. Cut-through
3. Fragment-free routing
4. Packet filtering

Correct Answer: 2. Cut-through

Explanation :-

Cut-through switching allows a switch to begin forwarding a frame before receiving the entire frame. After reading enough information to identify the destination MAC address, the switch can start transmission through the appropriate interface. This can reduce forwarding latency compared with store-and-forward switching, which receives the complete frame and checks it before forwarding. Store-and-forward can provide stronger error checking because the entire frame is available for validation. The choice between switching methods involves considerations such as latency, error handling, and platform capabilities. Understanding these forwarding methods helps explain how Ethernet switches process frames.

Question 38. Which command displays detailed information about a Cisco IOS interface, including errors and traffic statistics?

1. show interfaces
2. show ip route
3. show users
4. show flash

Correct Answer: 1. show interfaces

Explanation :-

The show interfaces command provides detailed information about Cisco device interfaces. Depending on the interface, the output can include line and protocol status, bandwidth, encapsulation, packet counts, errors, collisions, input and output statistics, and other operational information. This makes the command valuable for troubleshooting physical and data-link problems. show ip route focuses on routing information, show users displays active user sessions, and show flash provides information about files stored in flash memory. Administrators often use interface statistics to identify symptoms such as errors, drops, or abnormal traffic conditions.

Question 39. What is the primary purpose of an access control list (ACL) on a router or Layer 3 switch?

1. To assign MAC addresses to hosts
2. To provide wireless encryption
3. To filter traffic according to defined criteria
4. To synchronize device clocks

Correct Answer: 3. To filter traffic according to defined criteria

Explanation :-

An access control list (ACL) contains rules that permit or deny traffic according to criteria such as source and destination IP addresses, protocols, and ports. ACLs can be applied to interfaces or used by specific services to control traffic flows. They are commonly used to restrict unwanted access, limit network communication, and implement security policies. ACLs do not assign MAC addresses, synchronize clocks, or inherently provide wireless encryption. Administrators must consider rule order because ACL entries are evaluated sequentially, and traffic that does not match an explicit permit is subject to the applicable implicit deny behavior.

Question 40. Which command shows the Cisco IOS software version and basic hardware information?

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

Correct Answer: 2. show version

Explanation :-

The show version command provides information about the Cisco IOS software version, device model, system uptime, hardware resources, boot image, and other platform details. It is commonly used during troubleshooting, inventory checks, and software-version verification. show running-config displays the active configuration, while show ip interface brief provides a concise interface and IP status summary. show controllers is used for more specialized hardware information. Knowing the appropriate show command allows administrators to quickly obtain the information needed for configuration verification, troubleshooting, and operational analysis.