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Question 81:
What is the purpose of the DHCP protocol in networking?
A To assign static IP addresses to devices
B To dynamically assign IP addresses to devices
C To route data between different networks
D To manage DNS queries and responses
Correct Answer: B
Explanation:
The correct answer is B, DHCP (Dynamic Host Configuration Protocol) dynamically assigns IP addresses to devices on a network. Instead of manually configuring each device with an IP address, DHCP automates the process. A DHCP server manages a pool of available IP addresses and assigns them to devices as they join the network.
When a device connects to the network, it sends a DHCP request to the server. The DHCP server then selects an available IP address and assigns it to the device. Along with the IP address, the server may also provide other network configuration information, such as the default gateway, DNS servers, and subnet mask.
This protocol simplifies network administration, especially in large environments where managing IP addresses manually would be time-consuming and error-prone. It also reduces the risk of IP address conflicts, which can occur if two devices are accidentally assigned the same static IP address.
- A: Static IP addresses are manually assigned and are not the function of DHCP.
- C: Routing data between different networks is handled by routers, not DHCP.
- D: DNS queries and responses are managed by DNS servers, not by DHCP.
In summary, DHCP simplifies network configuration by automatically assigning IP addresses and other necessary information to devices on a network.
Question 82:
Which of the following layers of the OSI model is responsible for providing error detection and flow control?
A Physical layer
B Data Link layer
C Network layer
D Transport layer
Correct Answer: D
Explanation:
The correct answer is D, the Transport layer. The Transport layer (Layer 4) is responsible for ensuring the reliable transmission of data across a network. It provides error detection, error recovery, and flow control mechanisms, which are necessary for ensuring that data is delivered accurately and efficiently from the sender to the receiver.
One of the key protocols at this layer is TCP (Transmission Control Protocol), which guarantees reliable data delivery through mechanisms like acknowledgments, retransmissions, and sequence numbers. If data is lost or corrupted during transmission, TCP can request that the data be retransmitted, ensuring reliable communication.
Another important feature of the Transport layer is flow control, which prevents congestion and ensures that the sender does not overwhelm the receiver with too much data too quickly. This is typically achieved using techniques like windowing in TCP.
- A: The Physical layer (Layer 1) is responsible for transmitting raw bits over a physical medium, not for error detection or flow control.
- B: The Data Link layer (Layer 2) handles framing, error detection, and access control within a local network but does not manage end-to-end error recovery or flow control like the Transport layer.
- C: The Network layer (Layer 3) is responsible for routing packets between different networks and does not provide error recovery or flow control mechanisms for end-to-end communication.
In summary, the Transport layer is responsible for error detection, flow control, and reliable data delivery across the network.
Question 83:
What is the purpose of VLANs in a network?
A To create multiple broadcast domains within a single physical network
B To increase the physical distance between network devices
C To provide a secure tunnel for remote access
D To assign IP addresses to devices within a network
Correct Answer: A
Explanation:
The correct answer is A, VLANs (Virtual Local Area Networks) are used to create multiple broadcast domains within a single physical network. This means that devices within the same VLAN can communicate with each other without affecting devices in other VLANs. VLANs help segment a network into smaller, manageable sections, improving network performance and security.
By creating multiple VLANs, network administrators can isolate traffic within each VLAN. For example, sensitive data can be kept separate from general network traffic, enhancing security. Additionally, VLANs reduce the size of broadcast domains, which helps to minimize unnecessary broadcast traffic, leading to improved network efficiency.
VLANs are configured on network switches, and each switch port can be assigned to a specific VLAN. When devices are connected to that port, they become part of the VLAN associated with that port. This allows for logical segmentation of the network, regardless of the physical locations of the devices.
- B: VLANs do not increase the physical distance between devices; they are used to logically segment a network.
- C: A secure tunnel for remote access is typically provided by VPNs (Virtual Private Networks), not VLANs.
- D: VLANs do not assign IP addresses. IP address assignment is typically handled by DHCP or manually configured.
In summary, VLANs are used to segment a network into smaller broadcast domains, improving performance and security within the network.
Question 84:
Which of the following IP address ranges are reserved for private use?
A 10.0.0.0 to 10.255.255.255
B 192.168.0.0 to 192.168.255.255
C 172.16.0.0 to 172.31.255.255
D All of the above
Correct Answer: D
Explanation:
The correct answer is D, all of the above IP address ranges are reserved for private use. These private IP address ranges are specified in RFC 1918 and are used for internal networking purposes. Devices using these IP addresses cannot be directly accessed from the public internet, providing an extra layer of security.
The three private address ranges are:
- 10.0.0.0 to 10.255.255.255 (Class A)
- 172.16.0.0 to 172.31.255.255 (Class B)
- 192.168.0.0 to 192.168.255.255 (Class C)
These private addresses are typically used within local networks, and routers or firewalls typically use NAT (Network Address Translation) to allow devices with private IP addresses to communicate with external networks, such as the internet.
- A, B, C: Each of these ranges is reserved for private use, and they are not routable on the public internet. They are intended for internal use within private networks.
In summary, the IP address ranges 10.0.0.0 to 10.255.255.255, 172.16.0.0 to 172.31.255.255, and 192.168.0.0 to 192.168.255.255 are reserved for private use and are commonly used in internal networks.
Question 85:
Which of the following protocols is responsible for securely transferring files over the internet?
A FTP
B HTTP
C SFTP
D SNMP
Correct Answer: C
Explanation:
The correct answer is C, SFTP (Secure File Transfer Protocol). SFTP is an extension of the SSH (Secure Shell) protocol and is used to securely transfer files over a network. It provides encryption and ensures the confidentiality and integrity of data during transmission. SFTP is widely used for securely moving files between computers over the internet or within private networks.
Unlike FTP (File Transfer Protocol), which transmits data in plain text and is not secure, SFTP encrypts both the commands and data, preventing unauthorized access to sensitive information. SFTP operates over an encrypted SSH connection, ensuring that all file transfers are protected from eavesdropping and tampering.
- A: FTP is not secure and does not provide encryption, making it unsuitable for transferring sensitive data.
- B: HTTP is used for web page transmission, not for securely transferring files.
- D: SNMP (Simple Network Management Protocol) is used for network management and monitoring, not for file transfer.
In summary, SFTP is the secure protocol used for file transfers, ensuring encryption and data protection during transmission.
Question 86:
Which protocol is used for secure communication between a client and a server over the internet?
A HTTP
B HTTPS
C FTP
D SMTP
Correct Answer: B
Explanation:
The correct answer is B, HTTPS (HyperText Transfer Protocol Secure). HTTPS is a secure version of the standard HTTP (HyperText Transfer Protocol) used for transmitting web data. The key difference between HTTP and HTTPS is that HTTPS includes an additional layer of security provided by SSL (Secure Sockets Layer) or TLS (Transport Layer Security) protocols. These protocols encrypt the data being transferred, ensuring that sensitive information like passwords, credit card numbers, and personal data is protected from interception by malicious third parties.
HTTPS is particularly critical for protecting user data when accessing websites that involve financial transactions, social media logins, or any site requiring personal information. In fact, modern web browsers like Google Chrome and Mozilla Firefox will display a warning for users attempting to access websites that are not using HTTPS, as these sites are considered insecure.
The SSL/TLS encryption mechanism works by creating a secure, encrypted connection between the web browser (client) and the web server. When a user enters a website with HTTPS, a handshake process occurs in the background, where the client and server exchange keys to establish a secure connection. Once the connection is established, data is encrypted, preventing anyone on the network from viewing or altering the content of the communication.
- A (HTTP): HTTP is the foundation of data communication on the web but does not provide any encryption. As a result, the information exchanged between the client and server can be intercepted or tampered with.
- C (FTP): FTP (File Transfer Protocol) is used to transfer files between computers but is not secure by default. It transmits data in plain text, which means passwords and files are vulnerable to interception.
- D (SMTP): SMTP (Simple Mail Transfer Protocol) is used for sending emails, but like FTP, it is not secure unless additional protocols like SMTPS are used.
HTTPS ensures that user data remains private and that the communication between the client and server is protected from eavesdropping, which is particularly vital in today’s cyber-threat landscape.
Question 87:
Which layer of the OSI model is responsible for end-to-end communication and error recovery?
A Network layer
B Data Link layer
C Transport layer
D Application layer
Correct Answer: C
Explanation:
The correct answer is C, the Transport layer (Layer 4) of the OSI model. The Transport layer is responsible for ensuring reliable data transfer across networks. It provides end-to-end communication and is responsible for managing error recovery, data integrity, and flow control, all of which are critical for guaranteeing that data sent from one device reaches its destination without corruption or loss.
At the heart of the Transport layer is TCP (Transmission Control Protocol), a protocol that establishes reliable communication between two devices over the internet. TCP guarantees that packets are delivered in order, retransmits lost packets, and checks for errors using techniques such as checksums and sequence numbers. This level of reliability is essential for applications where data integrity is crucial, such as file transfers or web browsing.
Another protocol in the Transport layer is UDP (User Datagram Protocol), which, unlike TCP, is connectionless. While UDP doesn’t guarantee delivery or error recovery, it is often preferred in applications that require fast communication, such as video streaming or gaming, where the speed of data transmission is more important than the reliability of every individual packet.
The Transport layer also handles flow control, ensuring that the receiving device can handle the amount of data being sent. It prevents the sender from overwhelming the receiver with too much data at once, which could lead to network congestion or packet loss.
- A (Network layer): The Network layer (Layer 3) is responsible for routing data between different networks, but it does not handle end-to-end communication or error recovery. It uses IP (Internet Protocol) to determine the best path for data to travel across the network.
- B (Data Link layer): The Data Link layer (Layer 2) is responsible for node-to-node communication within the same network segment. It handles the framing of data into packets and provides error detection at a local level (through CRC checks), but it doesn’t perform end-to-end error recovery or flow control.
- D (Application layer): The Application layer (Layer 7) deals with user interaction, such as providing web browsers or email services. While it interacts with the end user, it doesn’t handle the underlying transport of data or error recovery.
In summary, the Transport layer is crucial for ensuring reliable, error-free communication between devices over a network and provides the necessary tools for error recovery and flow control.
Question 88:
Which type of cable is commonly used to connect a computer to a switch in a local area network (LAN)?
A Crossover cable
B Rollover cable
C Straight-through cable
D Fiber optic cable
Correct Answer: C
Explanation:
The correct answer is C, Straight-through cable. Straight-through cables are the most commonly used type of Ethernet cables in LAN environments. These cables are designed to connect network devices such as computers, printers, or servers to network switches, routers, or hubs.
Straight-through cables use RJ45 connectors and consist of twisted pairs of wires. The wiring scheme follows the T568A or T568B standard, where the pins on both ends of the cable are configured in a straight-through fashion. This means that each wire at one end of the cable is aligned with the same pin number on the opposite end.
This cable is ideal for connecting devices like computers to switches because the network switch expects to receive data on one set of pins and transmit it on another. The straight-through cable ensures that data flows correctly from the sending device to the receiving device without causing any misrouting or signal issues.
- A (Crossover cable): Crossover cables are used to directly connect two similar devices (such as two computers or two switches) without the need for a router or hub. In a crossover cable, the transmit and receive pairs are swapped between the two ends.
- B (Rollover cable): A rollover cable is typically used to connect a computer’s serial port to a router’s console port for configuration purposes. It is not used for normal data communication in a LAN.
- D (Fiber optic cable): Fiber optic cables are used for high-speed, long-distance communication between networks or for the backbone of large enterprise networks. While fiber optic cables offer higher performance, they are not typically used for connecting individual devices like computers to switches.
In summary, straight-through cables are commonly used to connect devices like computers to switches in a local area network, providing reliable communication.
Question 89:
Which of the following is an example of a Class B private IP address range?
A 10.0.0.0 to 10.255.255.255
B 172.16.0.0 to 172.31.255.255
C 192.168.0.0 to 192.168.255.255
D 224.0.0.0 to 239.255.255.255
Correct Answer: B
Explanation:
The correct answer is B, 172.16.0.0 to 172.31.255.255. This is the private IP address range defined for Class B networks as per RFC 1918. The private address space is reserved for use in private networks and is not routable on the public internet. The private IP ranges allow organizations to create internal networks without the need for globally unique IP addresses.
This range of 172.16.0.0 to 172.31.255.255 provides over 1 million unique IP addresses, making it suitable for medium-sized organizations that require many devices to be connected to their internal network. These IP addresses are commonly used for private networks and are often assigned to devices via DHCP or manually configured.
The other ranges are also private IP address ranges, but they correspond to different address classes:
- A (10.0.0.0 to 10.255.255.255): This range is a Class A private address range. It provides a very large number of IP addresses (over 16 million), making it ideal for very large networks.
- C (192.168.0.0 to 192.168.255.255): This range is a Class C private address range, commonly used for smaller networks (providing up to 65,536 addresses).
- D (224.0.0.0 to 239.255.255.255): This is the multicast address range, used for one-to-many communication across networks.
In summary, the private IP address range for Class B is 172.16.0.0 to 172.31.255.255, and it is commonly used for medium to large internal networks.
Question 90:
What is the primary function of a router in a network?
A To switch data frames within a local network
B To assign IP addresses to devices on a network
C To forward data packets between different networks
D To prevent unauthorized access to the network
Correct Answer: C
Explanation:
The correct answer is C, the primary function of a router is to forward data packets between different networks. A router operates at the Network layer (Layer 3) of the OSI model and is responsible for determining the best path for data packets to travel across networks. It does this by using routing tables and routing protocols like RIP (Routing Information Protocol), OSPF (Open Shortest Path First), or BGP (Border Gateway Protocol).
A router essentially connects multiple networks and allows communication between them, whether they are LANs (Local Area Networks) or WANs (Wide Area Networks). It plays a crucial role in IP addressing and packet forwarding, ensuring that data from a source device reaches its destination device through one or more intermediary networks.
Routers are also responsible for implementing Network Address Translation (NAT), which enables private IP addresses to be used in internal networks and then translated to public IP addresses when communicating over the internet. This helps conserve the limited number of publicly routable IP addresses.
- A (Switching data frames within a local network): This is the job of a switch, not a router. A switch operates at the Data Link layer (Layer 2) and is used to forward frames within a local network.
- B (Assigning IP addresses to devices): This function is typically handled by a DHCP server, not a router, although routers can provide DHCP services in some cases.
- D (Preventing unauthorized access): This function is typically handled by firewalls or security devices, not by routers. While routers may have some security features, their primary job is routing packets between networks.
In summary, routers are essential for connecting different networks and ensuring that data packets are forwarded to the correct destination. They facilitate communication between devices on different networks, and they also handle IP routing and network address translation.
Question 91:
What type of device is used to connect a computer to a local network (LAN)?
A Modem
B Switch
C Router
D Hub
Correct Answer: B
Explanation:
The correct answer is B, a switch is the most common device used to connect a computer to a local area network (LAN). A switch operates at the Data Link layer (Layer 2) of the OSI model and is responsible for forwarding data frames between devices within the same network. When a computer sends data over the network, the switch uses the MAC address to determine which device on the network should receive the data, thus facilitating communication between computers, printers, or other devices connected to the same LAN.
Switches are more intelligent than hubs, as they can differentiate between the devices connected to each port and only forward the data to the device that needs it, reducing unnecessary traffic. In contrast, hubs broadcast data to all connected devices, making the network less efficient and more prone to collisions.
- A (Modem): A modem is used to connect a local network to the internet by converting digital signals from a computer into analog signals that can be transmitted over telephone lines or cable. While a modem is crucial for internet connectivity, it does not connect devices within a local network.
- C (Router): A router connects multiple networks, typically a local network (LAN) to the internet (WAN). Routers are responsible for forwarding data between networks, managing IP addresses, and providing features like NAT (Network Address Translation). While routers are used to manage traffic between networks, they are not primarily used to connect devices within a local network.
- D (Hub): A hub is a basic networking device that connects multiple devices in a network, but it is outdated due to its inefficiency in managing network traffic. Unlike a switch, a hub broadcasts data to all devices on the network, causing unnecessary network traffic.
In conclusion, a switch is the most appropriate device for connecting a computer to a local network, as it efficiently forwards data only to the intended recipient.
Question 92:
What is the primary purpose of a VLAN in a network?
A To route traffic between different subnets
B To segment a network into different logical groups
C To provide security by blocking external traffic
D To enable multicast communication within a network
Correct Answer: B
Explanation:
The correct answer is B, the primary purpose of a VLAN (Virtual Local Area Network) is to segment a network into different logical groups. A VLAN allows network administrators to create separate broadcast domains within the same physical network. This means that devices in different VLANs cannot communicate directly with each other without the help of a router or Layer 3 switch, even if they are physically connected to the same network infrastructure.
The segmentation provided by VLANs improves network performance, security, and management. By grouping devices into VLANs based on function, department, or project, it is possible to limit broadcast traffic to specific segments of the network, which improves efficiency. For example, a company might create separate VLANs for HR, Finance, and IT departments, each with its own broadcast domain. This also ensures that broadcast traffic from one department does not overwhelm the entire network.
VLANs are configured on switches, which tag Ethernet frames with a VLAN identifier (VLAN ID) to maintain logical separation between different VLANs on the same physical switch. 802.1Q is the standard for VLAN tagging.
- A (Routing traffic between subnets): Routing between different subnets is typically performed by a router or Layer 3 switch, not by VLANs. While VLANs can be used to create separate subnets, routing is required for communication between them.
- C (Providing security by blocking external traffic): While VLANs can help improve security by isolating different parts of the network, their primary function is not to block external traffic. Security policies are typically enforced by firewalls or access control lists (ACLs).
- D (Enabling multicast communication): VLANs do not specifically enable multicast communication. However, multicast traffic can be managed within a VLAN if necessary. Multicast communication is a method of sending data from one device to multiple devices.
In summary, VLANs provide logical segmentation of networks, which improves performance, security, and overall network management.
Question 93:
What is the purpose of DHCP in a network?
A To assign IP addresses to devices automatically
B To encrypt data between devices
C To manage routing tables between routers
D To convert digital data into analog signals
Correct Answer: A
Explanation:
The correct answer is A, DHCP (Dynamic Host Configuration Protocol) is used to automatically assign IP addresses to devices on a network. When a device such as a computer or smartphone connects to a network, it needs an IP address to communicate with other devices on the network and beyond. Without DHCP, each device would need to be manually configured with a static IP address, which is inefficient and prone to errors.
DHCP works by assigning dynamic IP addresses from a pool of available addresses. The DHCP server maintains a list of IP addresses and, when a device requests an IP address, it assigns one from the available pool. The assigned IP address is typically leased to the device for a specific period, after which the lease expires, and the device must request a new IP address. DHCP also provides other important configuration information, such as the default gateway, subnet mask, and DNS servers.
This process significantly simplifies the management of IP addresses in a network, especially in large environments where manual IP address configuration would be impractical.
- B (Encrypting data between devices): Encryption is typically handled by protocols such as SSL/TLS, not DHCP. While DHCP provides network configuration information, it does not perform any encryption.
- C (Managing routing tables between routers): Managing routing tables is the job of routers, not DHCP. Routing protocols such as RIP, OSPF, and BGP are used to manage routing tables.
- D (Converting digital data into analog signals): This function is typically performed by a modem and is unrelated to DHCP. A modem converts digital signals from a computer into analog signals that can be transmitted over phone lines or cable networks.
In summary, DHCP automates the assignment of IP addresses and network configuration information to devices, making network administration more efficient and less error-prone.
Question 94:
Which of the following is a characteristic of a full-duplex communication system?
A Data can be sent in both directions simultaneously
B Data can only be sent in one direction at a time
C The connection is half the speed of a simplex connection
D The connection only allows one device to transmit at a time
Correct Answer: A
Explanation:
The correct answer is A, in a full-duplex communication system, data can be sent in both directions simultaneously. Full-duplex communication allows devices to both transmit and receive data at the same time, which improves efficiency and communication speed. This type of communication is commonly seen in technologies such as cell phones, telephones, and Ethernet networks.
In a full-duplex system, the communication channel is used to send data in both directions without interruption. This is in contrast to half-duplex communication, where data can only flow in one direction at a time, and simplex communication, where data can only flow in one direction without any ability to receive data.
For example, in a full-duplex Ethernet network, devices like computers and switches can send and receive data simultaneously, which maximizes network throughput and reduces communication delays.
- B (Data can only be sent in one direction at a time): This describes a half-duplex communication system, not full-duplex. In half-duplex communication, devices take turns sending and receiving data.
- C (Connection is half the speed of a simplex connection): This statement is incorrect. Simplex communication is one-way, and there is no direct comparison of speed between simplex and half-duplex systems in terms of the connection speed.
- D (Connection only allows one device to transmit at a time): This describes half-duplex communication, where devices alternate between sending and receiving data.
In summary, full-duplex communication allows for bidirectional data transfer simultaneously, which is crucial for modern communication systems.
Question 95:
Which of the following is a commonly used routing protocol in large-scale networks?
A RIP
B ARP
C OSPF
D SMTP
Correct Answer: C
Explanation:
The correct answer is C, OSPF (Open Shortest Path First). OSPF is a widely used Link-State routing protocol, which is particularly effective in large-scale enterprise networks. It is designed to efficiently calculate the best path for data to travel through a complex network by considering the current state of the network links and dynamically updating routing tables. OSPF is an interior gateway protocol (IGP) that operates within a single autonomous system, making it ideal for larger networks with multiple routers and subnets.
OSPF uses a hierarchical structure with multiple areas to reduce the size of the routing tables and improve scalability. It is also faster at converging when network changes occur, ensuring minimal downtime or routing loops. OSPF is a more scalable and efficient protocol compared to older protocols like RIP (Routing Information Protocol).
- A (RIP): RIP is an older distance-vector routing protocol that is still used in some smaller networks but is not suitable for large-scale networks due to its limitations in scalability and slower convergence times.
- B (ARP): ARP (Address Resolution Protocol) is not a routing protocol. It is used to map IP addresses to MAC addresses within a local network, allowing devices to communicate with each other at the data link layer.
- D (SMTP): SMTP (Simple Mail Transfer Protocol) is an application layer protocol used for sending emails. It is unrelated to routing.
In conclusion, OSPF is a preferred routing protocol for large-scale networks due to its efficiency, scalability, and ability to adapt to network changes quickly.
Question 96:
Which of the following commands is used to view the routing table on a Cisco router?
A show ip route
B show ip interface brief
C show running-config
D show version
Correct Answer: A
Explanation:
The correct answer is A, the show ip route command is used to display the routing table on a Cisco router. This command shows the routes that the router knows about, including both directly connected networks and remote networks that the router has learned about through routing protocols like RIP, OSPF, or BGP.
The routing table is a critical part of a router’s function, as it helps the router decide where to forward incoming packets. The routing table will include various entries that specify the destination network, the next-hop address, the outgoing interface, and the route’s administrative distance (which represents the trustworthiness of a route).
- B (show ip interface brief): This command is used to display a summary of the router’s interfaces, including their IP addresses and operational status. It doesn’t show the routing table.
- C (show running-config): This command displays the current configuration of the router, including interface settings, routing protocols, and other configuration parameters, but it doesn’t specifically show the routing table.
- D (show version): This command displays the router’s version information, such as the software version, hardware details, and uptime, but it doesn’t display the routing table.
In summary, show ip route is the correct command for viewing the routing table on a Cisco router, which is essential for understanding how the router routes traffic.
Question 97:
What does NAT (Network Address Translation) do in a network?
A It assigns IP addresses to devices within a local network
B It translates private IP addresses to public IP addresses
C It routes packets between different subnets
D It encrypts data sent over the network
Correct Answer: B
Explanation:
The correct answer is B, NAT (Network Address Translation) translates private IP addresses to public IP addresses. This process is typically used on routers and firewalls that are situated between a local network (using private IP addresses) and the internet (using public IP addresses). NAT helps manage the limited pool of public IP addresses by allowing multiple devices on a local network to share a single public IP address when accessing the internet.
There are different types of NAT, such as Static NAT (where a private IP is mapped to a specific public IP) and Dynamic NAT (where a private IP is mapped to an available public IP from a pool). PAT (Port Address Translation) is a form of NAT where multiple private IP addresses are mapped to a single public IP address using different port numbers.
By using NAT, organizations can maintain internal IP address space (often using private IP ranges like 192.168.x.x, 10.x.x.x, or 172.16.x.x) and avoid the need for a unique public IP address for every device, thereby conserving the number of public IP addresses required.
- A (Assigning IP addresses): While NAT deals with IP address translation, it is not responsible for assigning IP addresses. This is done by DHCP (Dynamic Host Configuration Protocol).
- C (Routing packets between subnets): Routing between subnets is handled by routers using routing protocols like OSPF or RIP, not NAT.
- D (Encrypting data): Encryption is not a function of NAT. Encryption is typically handled by VPNs or SSL/TLS protocols.
In conclusion, NAT is a method for translating private IP addresses to public IP addresses, allowing devices in a local network to access external networks like the internet using a shared public IP.
Question 98:
Which of the following best describes a Layer 2 switch?
A A device that forwards traffic based on IP addresses
B A device that forwards traffic based on MAC addresses
C A device that routes traffic between different subnets
D A device that encrypts data to secure it during transmission
Correct Answer: B
Explanation:
The correct answer is B, a Layer 2 switch forwards traffic based on MAC addresses. Layer 2 switches operate at the Data Link layer of the OSI model and are primarily responsible for forwarding frames between devices within the same local network (LAN). When a switch receives a frame, it looks at the MAC address in the frame’s header to determine the destination device and forwards the frame to the appropriate port.
Unlike routers, which operate at Layer 3 and forward traffic between different networks based on IP addresses, a Layer 2 switch does not need to examine the packet’s IP address. Instead, it uses the MAC address table, which it builds dynamically by learning the MAC addresses of devices that are connected to its ports.
Layer 2 switches are also capable of VLAN (Virtual Local Area Network) segmentation, allowing network administrators to logically group devices into separate broadcast domains, even if they are on the same physical network.
- A (Forwarding traffic based on IP addresses): This describes a Layer 3 router or Layer 3 switch, not a Layer 2 switch. Routers forward packets based on IP addresses, which are used for routing traffic between different subnets.
- C (Routing traffic between different subnets): This function is performed by routers, not Layer 2 switches. Routers are responsible for routing traffic between different IP subnets or networks.
- D (Encrypting data): Encryption is not a function of Layer 2 switches. Encryption is handled by protocols such as SSL/TLS or VPNs to secure data during transmission.
In summary, a Layer 2 switch operates based on MAC addresses and is used primarily for local communication within a single network segment.
Question 99:
Which protocol is used to prevent loops in a switched network?
A ICMP
B ARP
C STP
D DHCP
Correct Answer: C
Explanation:
The correct answer is C, STP (Spanning Tree Protocol) is used to prevent loops in a switched network. STP is a Link Layer protocol defined by the IEEE 802.1D standard that ensures a loop-free topology in Ethernet networks. In a network with multiple switches, loops can occur if there are redundant paths between switches. These loops can cause broadcast storms, MAC table instability, and overall network congestion.
STP works by electing a root bridge and then selecting root ports and designated ports on other switches to create a tree-like structure of the network. If a loop is detected, STP will block certain redundant paths to break the loop, ensuring that there is only one active path between any two devices in the network.
- A (ICMP): ICMP (Internet Control Message Protocol) is used for error reporting and diagnostic functions like ping and traceroute but does not address loops in a network.
- B (ARP): ARP (Address Resolution Protocol) is used to map IP addresses to MAC addresses in a local network. ARP does not prevent loops.
- D (DHCP): DHCP (Dynamic Host Configuration Protocol) is used for dynamically assigning IP addresses to devices on a network, but it does not deal with preventing loops in a switched network.
In summary, STP is the protocol used to prevent loops in switched networks, ensuring that there are no redundant, active paths that could cause broadcast storms or other issues.
Question 100:
Which layer of the OSI model is responsible for establishing, maintaining, and terminating connections between devices?
A Transport Layer
B Session Layer
C Network Layer
D Data Link Layer
Correct Answer: B
Explanation:
The correct answer is B, the Session Layer (Layer 5) of the OSI model is responsible for establishing, maintaining, and terminating connections between devices. The Session layer manages the sessions or dialogues between applications running on different devices. It controls the flow of information, ensures that data is properly synchronized between communicating devices, and provides error recovery during communication sessions.
The session layer is responsible for managing the dialogue between two devices and may support functions such as authentication, synchronization, and checkpointing to ensure that the communication can be resumed if interrupted.
A (Transport Layer): The Transport Layer (Layer 4) is responsible for end-to-end communication and reliability. It ensures data is delivered accurately between devices by using protocols like TCP (Transmission Control Protocol) and UDP (User Datagram Protocol). While the transport layer ensures reliable data transfer, the session layer focuses on managing the connection itself.
C (Network Layer): The Network Layer (Layer 3) is responsible for routing data between different networks and handling logical addressing (IP addresses). It determines the best path for data to travel across the network, but it does not manage connections between devices.
D (Data Link Layer): The Data Link Layer (Layer 2) is responsible for node-to-node communication within a local network. It handles error detection and correction and manages MAC addresses, but it does not establish or terminate connections between devices.
