N10-009 Networking Concepts — 50 Questions

Question 1

A network administrator is troubleshooting a connectivity issue and suspects the problem is related to the physical cabling. At which layer of the OSI model should the administrator begin their investigation?

Accepted Answer

Physical layer. The Physical layer (Layer 1) is the correct starting point because the administrator suspects the problem is related to physical cabling. The Physical layer defines the electrical, mechanical, and procedural specifications for transmitting raw bits over a physical medium, such as copper or fiber optic cables. Troubleshooting at this layer involves checking for cable faults, signal degradation, or improper termination before moving up the OSI stack.

Answer

Transport layer

Answer

Data Link layer

Answer

Network layer

Question 2

A device is configured with IP address 192.168.1.130 and subnet mask 255.255.255.192. What is the network address of this device?

Accepted Answer

192.168.1.128. The network address is found by performing a bitwise AND between the IP address 192.168.1.130 and the subnet mask 255.255.255.192. The mask 255.255.255.192 has a prefix length of /26, meaning the first 26 bits are the network portion. 192.168.1.130 in binary is 11000000.10101000.00000001.10000010, and the mask is 11111111.11111111.11111111.11000000; the AND yields 11000000.10101000.00000001.10000000, which is 192.168.1.128.

Answer

192.168.1.0

Answer

192.168.1.192

Answer

192.168.1.64

Question 3

A network technician is explaining the concept of encapsulation to a junior technician. At which OSI layer does a packet get encapsulated with a source and destination IP address?

Accepted Answer

Layer 3. At Layer 3 (the Network layer), the packet is encapsulated with a source and destination IP address. This is defined by the Internet Protocol (IP), which handles logical addressing and routing across networks. The IP header is added to the payload from the upper layers, creating a packet that can be forwarded by routers.

Answer

Layer 2

Answer

Layer 4

Answer

Layer 1

Question 4

A network engineer is designing a new IPv6 addressing scheme. The company has been assigned a /48 prefix and needs to support up to 250 subnets. Which subnet size should be used to minimize waste while meeting the requirement?

Accepted Answer

/56. A /56 subnet provides 256 subnets (2^(56-48) = 2^8 = 256), which meets the requirement of up to 250 subnets with minimal waste. A /48 prefix is the site-level allocation, and using a /56 subnet mask leaves 8 bits for subnetting, offering exactly the needed capacity without over-allocating address space.

Answer

/52

Answer

/64

Answer

/60

Question 5

A network technician is explaining the difference between a hub and a switch to a junior technician. Which statement correctly describes a key difference between these devices?

Accepted Answer

A hub sends frames out all ports except the incoming port; a switch sends frames only to the port with the matching MAC address.. B is correct because a hub operates at Layer 1 (physical layer) and blindly repeats electrical signals out all ports except the incoming port, creating a single collision domain. In contrast, a switch operates at Layer 2 (data link layer) and uses the MAC address table to forward frames only to the specific port associated with the destination MAC address, reducing unnecessary traffic and creating separate collision domains per port.

Answer

A hub operates at Layer 2, while a switch operates at Layer 1.

Answer

A hub uses MAC addresses to make forwarding decisions, while a switch uses IP addresses.

Answer

A hub creates a separate collision domain for each port, while a switch creates a single collision domain.

Question 6

A network engineer needs to connect two network segments that use different physical media: one segment uses copper Ethernet and the other uses fiber optic. The device must forward frames based on MAC addresses and must not perform any routing. Which device should the engineer choose?

Accepted Answer

Bridge. A bridge operates at Layer 2, forwarding frames based on MAC addresses while connecting different physical media (e.g., copper to fiber). It does not perform routing, making it the correct choice for this scenario. Unlike a media converter, a bridge also provides segmentation and collision domain isolation.

Answer

Layer 3 switch

Answer

Media converter

Answer

Router

Question 7

A network engineer is troubleshooting a communication issue between two hosts. The engineer determines that the data is being segmented at the source and reassembled at the destination, but the segments are arriving out of order. Which OSI layer is responsible for sequencing the segments?

Accepted Answer

D) Transport layer. The Transport layer (Layer 4) is responsible for end-to-end communication, including segmentation, reassembly, and sequencing of data segments. Protocols like TCP use sequence numbers to order segments correctly at the destination, even if they arrive out of order. This ensures the upper layers receive a complete, ordered data stream.

Answer

A) Physical layer

Answer

B) Data Link layer

Answer

C) Network layer

Question 8

A network technician is assigned a subnet mask of 255.255.255.248. How many usable host addresses are available in this subnet?

Accepted Answer

A) 6. The subnet mask 255.255.255.248 corresponds to a /29 prefix length, which provides 2^(32-29) = 8 total addresses. Subtracting the network address and broadcast address leaves 8 - 2 = 6 usable host addresses.

Answer

B) 8

Answer

C) 14

Answer

D) 30

Question 9

A network technician is explaining the OSI model to a junior technician. The technician mentions that the Transport layer is responsible for end-to-end communication and data segmentation. Which protocol operates at the Transport layer?

Accepted Answer

TCP. TCP (Transmission Control Protocol) operates at Layer 4 (Transport) of the OSI model, providing reliable, connection-oriented end-to-end communication and data segmentation with sequencing and acknowledgment. It ensures data is delivered error-free and in order, directly fulfilling the described responsibilities.

Answer

IP

Answer

Ethernet

Answer

HTTP

Question 10

A network engineer is designing a subnet that can support at least 10 hosts. Which subnet mask would provide exactly 14 usable host addresses?

Accepted Answer

/28. A /28 subnet mask (255.255.255.240) provides 16 total addresses per subnet. Subtracting the network address and broadcast address leaves 14 usable host addresses, which exactly meets the requirement of at least 10 hosts.

Answer

/27

Answer

/29

Answer

/30

Question 11

Which of the following protocols is used to automatically assign IP addresses to devices on a network?

Accepted Answer

B) DHCP. DHCP (Dynamic Host Configuration Protocol) is the correct answer because it is specifically designed to automatically assign IP addresses and other network configuration parameters (such as subnet mask, default gateway, and DNS servers) to devices on a network. When a client device connects, it sends a DHCP Discover broadcast, and the DHCP server responds with an Offer, followed by a Request and Acknowledgment (DORA process), enabling plug-and-play connectivity.

Answer

A) DNS

Answer

C) ARP

Answer

D) ICMP

Question 12

Which of the following is a characteristic of UDP when compared to TCP?

Accepted Answer

C) UDP has lower overhead due to minimal header. UDP (User Datagram Protocol) has a minimal 8-byte header compared to TCP's 20-byte header, resulting in lower overhead and faster transmission. Unlike TCP, UDP does not provide reliability, flow control, or error recovery, making it ideal for real-time applications like VoIP or video streaming where speed is prioritized over guaranteed delivery.

Answer

A) UDP uses sequence numbers for ordering

Answer

B) UDP provides reliable data delivery

Answer

D) UDP requires a three-way handshake to establish a connection

Question 13

A network engineer needs to transfer a large database file from one server to another across a WAN link. The transfer must be reliable and guarantee that the data arrives without errors. Which transport layer protocol should the engineer use?

Accepted Answer

TCP. TCP (Transmission Control Protocol) is the correct choice because it provides reliable, connection-oriented data transfer with error checking, retransmission of lost packets, and in-order delivery. For a large database file transfer across a WAN link, TCP ensures the data arrives completely and without errors, which is essential for database integrity.

Answer

UDP

Answer

IP

Answer

ICMP

Question 14

A network device receives a frame and forwards it based on the destination MAC address. The device does not modify the frame and only floods unknown unicast frames. At which layer of the OSI model does this device operate?

Accepted Answer

Layer 2. This device operates at Layer 2 (Data Link Layer) because it forwards frames based on the destination MAC address, does not modify the frame, and floods unknown unicast frames. These behaviors are characteristic of a transparent bridge or switch, which uses a MAC address table to make forwarding decisions without examining IP addresses or modifying the frame. Layer 2 devices do not perform routing or alter the frame's content, distinguishing them from Layer 3 routers.

Answer

Layer 1

Answer

Layer 3

Answer

Layer 4

Question 15

A network device receives a frame on one port and forwards it out to all other ports. The device does not examine the destination MAC address. Which type of device is being described?

Accepted Answer

Hub. A hub operates at Layer 1 (physical layer) of the OSI model and simply repeats incoming electrical or optical signals out all other ports without any processing of the frame's destination MAC address. This behavior matches the description exactly: the device receives a frame on one port and forwards it out all other ports without examining the MAC address.

Answer

Switch

Answer

Bridge

Answer

Router

Question 16

A network engineer needs to assign IP addresses to a new subnet that will support exactly 25 devices. Which subnet mask would provide the minimum number of usable host addresses while still accommodating the requirement?

Accepted Answer

255.255.255.224 (/27). Option B (255.255.255.224, /27) provides 32 total addresses per subnet, with 30 usable host addresses (2^(32-27)-2 = 30). This is the smallest subnet that can accommodate exactly 25 devices, as /28 yields only 14 usable hosts and /26 yields 62, which is excessive.

Answer

255.255.255.240 (/28)

Answer

255.255.255.192 (/26)

Answer

255.255.255.128 (/25)

Question 17

A network engineer is designing a network and needs to ensure that broadcast traffic is contained within a single broadcast domain. Which of the following devices should be used to create these separate broadcast domains?

Accepted Answer

Router. A router operates at Layer 3 of the OSI model and does not forward broadcast frames by default, making it the correct device to segment a network into separate broadcast domains. Each interface on a router creates a distinct broadcast domain, ensuring that broadcast traffic is contained within that interface's subnet.

Answer

Hub

Answer

Bridge

Answer

Switch

Question 18

A network administrator wants to segment the network into multiple virtual LANs to reduce broadcast traffic. Which device is required to route traffic between these VLANs?

Accepted Answer

Router or Layer 3 switch. VLANs operate at Layer 2, isolating broadcast domains. To route traffic between different VLANs, a device that can forward packets based on Layer 3 IP addresses is required. A router or a Layer 3 switch (which performs hardware-based routing using ASICs) provides the necessary inter-VLAN routing functionality.

Answer

Layer 2 switch

Answer

Bridge

Answer

Hub

Question 19

A company needs a subnet that will support exactly 50 devices. Which subnet mask provides the minimum number of usable host addresses while still accommodating the requirement?

Accepted Answer

255.255.255.192 (/26). Option B (255.255.255.192, /26) provides 2^(32-26) - 2 = 62 usable host addresses, which is the smallest subnet that supports exactly 50 devices. A /27 yields only 30 usable addresses (too few), while a /25 yields 126 usable addresses (wasteful). The requirement is to minimize waste while meeting the need.

Answer

255.255.255.128 (/25)

Answer

255.255.255.224 (/27)

Answer

255.255.255.240 (/28)

Question 20

A network administrator is configuring BGP between two autonomous systems. Which BGP attribute is primarily used to influence inbound traffic to a particular AS?

Accepted Answer

MED (Multi-Exit Discriminator). The Multi-Exit Discriminator (MED) is a BGP attribute used to influence inbound traffic from a neighboring AS when multiple entry points exist. A lower MED value is preferred, allowing an AS to advertise to its neighbor which path should be used to reach it, thereby influencing traffic entering the local AS.

Answer

AS_PATH

Answer

Next Hop

Answer

Local Preference