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Question: 241. Which IPv4 subnet mask provides 62 usable host addresses in a traditional subnet?

1. 255.255.255.224
   2. 255.255.255.192
   3. 255.255.255.240
   4. 255.255.255.128

Correct Answer: 2. 255.255.255.192

Explanation:

 

A /26 subnet uses the mask 255.255.255.192 and provides 64 total IPv4 addresses. In a traditional subnet, one address identifies the network and another is reserved for the broadcast address, leaving 62 usable host addresses. A /27 subnet provides 30 usable addresses, a /28 provides 14, and a /25 provides 126. Understanding subnet sizes is important when planning IP address allocation and determining whether a subnet can accommodate the required number of devices. Therefore, 255.255.255.192 is the appropriate mask for 62 usable host addresses.

Question: 242. What is the primary purpose of a DHCP lease?

1. To reserve an Ethernet switch port permanently
   2. To encrypt DHCP messages
   3. To define how long a client can use assigned network configuration
   4. To convert hostnames into IP addresses

Correct Answer: 3. To define how long a client can use assigned network configuration

Explanation:

A DHCP lease defines the period for which a client may use an IP address and associated configuration supplied by a DHCP server. Before the lease expires, the client normally attempts to renew it so that its network configuration remains valid. Lease management allows DHCP servers to efficiently reuse addresses when clients leave the network. DHCP does not encrypt its messages by default, and DNS is responsible for hostname-to-IP resolution. Therefore, defining the duration of assigned network configuration is the primary purpose of a DHCP lease.

Question: 243. Which routing method requires an administrator to manually configure routes?

1. Static routing
   2. Dynamic routing
   3. Anycast routing
   4. Multicast routing

Correct Answer: 1. Static routing

Explanation:

Static routes are manually configured by a network administrator and remain in the routing table until they are changed or removed. They can be useful in small networks, for specific destinations, or when administrators require precise control over a path. Dynamic routing protocols, in contrast, exchange routing information and can automatically adapt to topology changes. Anycast and multicast describe traffic-addressing or delivery behaviors rather than the general distinction between manually configured and dynamically learned routes. Therefore, static routing is the method that requires manual route configuration.

Question: 244. What does the subnet prefix length /24 indicate in IPv4 addressing?

1. 24 host bits and 8 network bits
   2. 24 total usable hosts
   3. 24 network bits and 8 host bits
   4. 24 broadcast addresses

Correct Answer: 3. 24 network bits and 8 host bits

Explanation:

A /24 prefix means that the first 24 bits of a 32-bit IPv4 address identify the network portion, leaving 8 bits for host addressing. The equivalent subnet mask is 255.255.255.0. This provides 256 total addresses in the subnet, with 254 traditionally usable for hosts when the network and broadcast addresses are excluded. Prefix notation is a concise way to describe the network portion of an IPv4 address. Therefore, /24 represents 24 network bits and 8 host bits.

Question: 245. Which protocol is commonly used to discover the Layer 2 address of an IPv6 neighbor?

1. RARP
   2. NDP
   3. DHCPv4
   4. FTP

Correct Answer: 2. NDP

Explanation:

IPv6 uses Neighbor Discovery Protocol, or NDP, to perform functions that include discovering neighboring devices and resolving IPv6 addresses to link-layer addresses. NDP operates through ICMPv6 messages and supports several important IPv6 functions, including neighbor discovery, router discovery, and address resolution. IPv6 does not use ARP in the same manner as IPv4. RARP is obsolete, DHCPv4 applies to IPv4, and FTP is a file-transfer protocol. Therefore, NDP is the appropriate protocol for IPv6 neighbor and link-layer address discovery.

Question: 246. Which switching method immediately begins forwarding a frame after reading its destination MAC address?

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

Correct Answer: 4. Cut-through switching

Explanation:

Cut-through switching begins forwarding a frame after reading enough of the frame to determine its destination, rather than waiting for the entire frame to be received. This can reduce forwarding latency. Store-and-forward switching receives the complete frame before forwarding and can therefore perform more extensive frame checks. Fragment-free switching waits for a portion of the frame before forwarding to reduce the likelihood of forwarding collision fragments. Circuit switching is a different communication model. Therefore, cut-through switching is the method associated with low-latency forwarding based on early destination information.

Question: 247. What is the primary purpose of a firewall rule?

1. To define whether specified traffic should be permitted or denied
   2. To increase Ethernet cable speed
   3. To assign MAC addresses to clients
   4. To synchronize device clocks

Correct Answer: 1. To define whether specified traffic should be permitted or denied

Explanation:

Firewall rules define how traffic matching specified criteria should be handled. Criteria may include source and destination addresses, protocols, ports, interfaces, or other attributes depending on the firewall platform. A rule can permit, deny, reject, log, or otherwise process matching traffic. Firewalls therefore provide an important mechanism for controlling network communication according to an organization’s security policy. Ethernet speed, MAC address assignment, and clock synchronization are handled by other technologies. Thus, defining whether particular traffic is permitted or denied is a fundamental purpose of a firewall rule.

Question: 248. Which IPv4 address is a valid example of a link-local address?

1. 127.0.0.1
   2. 10.10.10.10
   3. 169.254.25.10
   4. 224.0.0.5

Correct Answer: 3. 169.254.25.10

Explanation:

The IPv4 range 169.254.0.0/16 is reserved for link-local addressing. A device may automatically select an address from this range when it cannot obtain a suitable 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 between networks. The address 127.0.0.1 is a loopback address, 10.10.10.10 is a private IPv4 address, and 224.0.0.5 is a multicast address. Therefore, 169.254.25.10 is a valid link-local example.

Question: 249. Which device typically operates primarily at Layer 2 of the OSI model?

1. Router
   2. Ethernet switch
   3. DNS server
   4. Application gateway

Correct Answer: 2. Ethernet switch

Explanation:

A traditional Ethernet switch primarily operates at Layer 2, the Data Link layer, where it forwards frames based on MAC addresses. Modern Layer 3 switches can also perform routing functions, but their switching functionality still relies on Layer 2 concepts. Routers primarily make forwarding decisions using Layer 3 IP information. DNS servers provide name-resolution services, while application gateways can operate at higher layers depending on their function. Therefore, an Ethernet switch is the device most directly associated with primary Layer 2 operation.

Question: 250. Which mechanism can prevent a switch port from accepting frames with unexpected source MAC addresses?

1. DHCP snooping
   2. Port security
   3. NTP authentication
   4. DNS filtering

Correct Answer: 2. Port security

Explanation:

Switch port security can restrict which source MAC addresses are permitted on a switch port. Depending on the configuration, administrators can statically specify allowed MAC addresses or allow the switch to learn addresses dynamically and enforce limits. If an unauthorized source MAC address appears, the switch can take a configured action such as dropping frames or placing the port into a protected state. DHCP snooping helps protect DHCP operations, NTP authentication protects time synchronization exchanges, and DNS filtering controls name-resolution requests. Therefore, port security is the appropriate feature.

Question: 251. Which routing protocol is classified as a link-state interior gateway protocol?

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

Correct Answer: 2. OSPF

Explanation:

OSPF, or Open Shortest Path First, is a link-state interior gateway protocol. OSPF routers exchange link-state information and build a topology database from which they calculate routes using the Shortest Path First algorithm. RIP is a distance-vector routing protocol, while BGP is primarily used for exchanging routing information between autonomous systems. FTP is not a routing protocol. OSPF is widely used in enterprise networks because it can support hierarchical designs and respond dynamically to topology changes. Therefore, OSPF is the correct link-state interior gateway protocol.

Question: 252. What is the primary purpose of a loopback interface on a network device?

1. To provide a stable logical interface independent of a physical port
   2. To connect an Ethernet cable directly to another switch
   3. To supply PoE power
   4. To create a physical backup cable

Correct Answer: 1. To provide a stable logical interface independent of a physical port

Explanation:

A loopback interface is a logical interface that is not tied to a specific physical network port. Because it can remain operational as long as the device’s underlying routing system is functioning, it is often used for management, routing protocol identification, monitoring, or other services that benefit from a stable address. A loopback interface does not physically connect devices, provide PoE, or create a backup cable. Therefore, providing a stable logical interface independent of a particular physical port is its primary advantage.

Question: 253. Which technology allows a network administrator to prioritize voice traffic over less time-sensitive traffic?

1. DNS
   2. NAT
   3. QoS
   4. ARP

Correct Answer: 3. QoS

Explanation:

Quality of Service, or QoS, provides mechanisms for classifying, marking, queuing, and prioritizing network traffic. Voice and video traffic can be sensitive to latency, jitter, and packet loss, so QoS policies can give these traffic classes preferential treatment when network resources become congested. DNS resolves names, NAT translates addresses, and ARP resolves IPv4 addresses to MAC addresses. QoS does not create additional bandwidth, but it can manage available capacity more effectively for important traffic classes. Therefore, QoS is the appropriate technology for prioritizing voice traffic.

Question: 254. Which IPv6 prefix is commonly used for link-local addresses?

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

Correct Answer: 1. FE80::/10

Explanation:

IPv6 link-local addresses use the FE80::/10 prefix. These addresses are automatically associated with interfaces and are used for communication on the local link. They are important for IPv6 neighbor discovery and other local-link operations and are not intended to be routed across network boundaries. The 2000::/3 range is used for global unicast addresses, FC00::/7 is associated with unique local addresses, and FF00::/8 identifies multicast addresses. Therefore, FE80::/10 is the correct prefix for IPv6 link-local addressing.

Question: 255. What does the term “collision domain” describe in an Ethernet network?

1. A group of devices sharing the same DNS server
   2. A group of devices where transmitted frames could potentially collide
   3. A group of routers using the same routing protocol
   4. A set of hosts sharing the same subnet mask only

Correct Answer: 2. A group of devices where transmitted frames could potentially collide

Explanation:

A collision domain is a network segment in which devices can potentially experience frame collisions when sharing a common transmission medium. Traditional Ethernet hubs created a single collision domain because all connected devices shared the same medium. Modern switched Ethernet greatly reduces collision domains because each switch port generally represents a separate collision domain, particularly when operating in full-duplex mode. DNS configuration, routing protocols, and subnet masks describe different network concepts. Therefore, a collision domain refers to the group of devices sharing a medium where frame collisions could occur.

Question: 256. Which protocol is commonly used by network devices to automatically discover neighboring devices and advertise basic device information?

1. CDP or LLDP
   2. SMTP
   3. DHCPv6
   4. SFTP

Correct Answer: 1. CDP or LLDP

Explanation:

CDP and LLDP are Layer 2 neighbor-discovery protocols that allow network devices to advertise and learn information about directly connected neighbors. Depending on the protocol and device implementation, information can include device identity, port details, capabilities, and network-related information. LLDP is an open IEEE standard, while CDP is a vendor-specific protocol commonly associated with Cisco devices. SMTP is an email protocol, DHCPv6 provides IPv6 configuration, and SFTP provides secure file transfer. Therefore, CDP or LLDP is appropriate for discovering directly connected network neighbors.

Question: 257. What is the main purpose of NAT in many IPv4 networks?

1. To replace Ethernet switching
   2. To synchronize routing tables
   3. To translate between private and public IPv4 addresses
   4. To create wireless SSIDs

Correct Answer: 3. To translate between private and public IPv4 addresses

Explanation:

Network Address Translation, or NAT, translates IP addresses between different addressing domains. A common use is translating private IPv4 addresses used inside an organization into a public IPv4 address for Internet access. Port Address Translation can allow many internal hosts to share a single public IPv4 address by tracking transport-layer ports. NAT does not replace Ethernet switching, synchronize routing tables, or create wireless SSIDs. Therefore, translating between private and public IPv4 addressing is a common and important purpose of NAT.

Question: 258. Which wireless frequency band generally provides more available non-overlapping channels and shorter range than 2.4 GHz?

1. 900 MHz
   2. 5 GHz
   3. AM radio
   4. Infrared

Correct Answer: 2. 5 GHz

Explanation:

The 5 GHz Wi-Fi band generally provides more channel capacity and more non-overlapping channel options than the traditional 2.4 GHz band, depending on the regulatory domain and channel configuration. However, higher-frequency wireless signals generally have shorter propagation range and may experience greater attenuation through walls and other obstacles. The 2.4 GHz band generally provides better range but has fewer available channels and is more susceptible to congestion from other devices. Therefore, 5 GHz is the appropriate choice among the listed options.

Question: 259. Which security principle gives a user only the permissions required to perform their assigned tasks?

1. Least privilege
   2. Open access
   3. Maximum privilege
   4. Shared authentication

Correct Answer: 1. Least privilege

Explanation:

The principle of least privilege means that users, devices, and applications should receive only the permissions necessary to perform their authorized tasks. Limiting privileges reduces the potential impact of compromised accounts, malicious software, and accidental changes. It also helps administrators maintain clearer control over access to sensitive resources. Open or excessive access provides broader permissions than necessary, while shared authentication can reduce accountability. Therefore, least privilege is the security principle that limits permissions to the minimum required for legitimate operations.

Question: 260. Which metric represents the variation in packet arrival time across a network?

1. Throughput
   2. Bandwidth
   3. Jitter
   4. MTU

Correct Answer: 3. Jitter

Explanation:

Jitter describes variation in packet arrival time. It is particularly important for real-time applications such as voice and video because inconsistent packet timing can reduce communication quality even when average latency is acceptable. Throughput measures the amount of data successfully transferred over a period, bandwidth describes the capacity of a communication link, and MTU defines the maximum packet size supported by a link. Monitoring jitter can therefore help administrators identify problems that affect time-sensitive traffic. Thus, jitter is the metric that represents variation in packet arrival time.