CompTIA Network+ (N10-008) - Networking Infrastructure & Protocols Flashcards

Question 1

What is the primary function of the OSI model's Data Link Layer?

Accepted Answer

The Data Link Layer (Layer 2) is responsible for physical addressing (MAC addresses), error detection, and controlling access to the physical medium. Its PDU is a `frame`.

Question 2

Name the four layers of the TCP/IP model and their corresponding OSI layers.

Accepted Answer

1.  **Application Layer:** (OSI Layers 5, 6, 7 - Session, Presentation, Application)
2.  **Transport Layer:** (OSI Layer 4 - Transport)
3.  **Internet Layer:** (OSI Layer 3 - Network)
4.  **Network Access Layer:** (OSI Layers 1, 2 - Physical, Data Link)

Question 3

Explain CIDR notation and provide an example.

Accepted Answer

CIDR (Classless Inter-Domain Routing) is a method for allocating IP addresses and routing IP packets. It uses a prefix length (e.g., `/24`) to indicate the number of bits in the IP address that represent the network portion. Example: `192.168.1.0/24` means the first 24 bits identify the network.

Question 4

What is the subnet mask for an IPv4 address with a `/27` CIDR prefix?

Accepted Answer

A `/27` prefix means 27 bits are for the network portion.
$27 	ext{ network bits} = 24 	ext{ full octets} + 3 	ext{ bits in the 4th octet}$
The subnet mask is `255.255.255.224`.
(Binary: `11111111.11111111.11111111.11100000`)

Question 5

Which standard port number is used by SSH (Secure Shell) for remote secure access?

Accepted Answer

SSH uses TCP port `22`.

Question 6

Which standard port number is used by DNS (Domain Name System) for name resolution?

Accepted Answer

DNS primarily uses UDP port `53` for queries and TCP port `53` for zone transfers.

Question 7

What are the standard port numbers for HTTP and HTTPS?

Accepted Answer

HTTP (Hypertext Transfer Protocol) uses TCP port `80`. HTTPS (HTTP Secure) uses TCP port `443`.

Question 8

Describe the primary function of the `ping` command.

Accepted Answer

The `ping` command is used to test the reachability of a host on an Internet Protocol (IP) network and to measure the round-trip time for messages sent from the originating host to a destination computer. It uses ICMP Echo Request/Reply packets.

Question 9

What is the purpose of the `traceroute` (or `tracert`) command?

Accepted Answer

The `traceroute` command maps the path an IP packet takes to reach a destination, displaying the IP addresses of intermediate routers (hops) and the time taken for each hop. It helps identify where connectivity issues might be occurring.

Question 10

How does `nslookup` (or `dig`) assist in network diagnostics?

Accepted Answer

`nslookup` (Windows/Linux) and `dig` (Linux/Unix) are command-line tools used to query DNS servers to obtain domain name or IP address mapping, or other DNS records. They help verify DNS resolution.

Question 11

What information does the `netstat` command provide?

Accepted Answer

The `netstat` (network statistics) command displays active TCP connections, listening ports, routing tables, and network interface statistics. It's useful for troubleshooting connectivity and identifying open ports.

Question 12

Differentiate between OSPF and BGP routing protocols.

Accepted Answer

-   **OSPF (Open Shortest Path First):** An Interior Gateway Protocol (IGP) used within an Autonomous System (AS). It's a link-state protocol that calculates the shortest path using Dijkstra's algorithm.
-   **BGP (Border Gateway Protocol):** An Exterior Gateway Protocol (EGP) used between different Autonomous Systems (ASes) on the internet. It's a path-vector protocol that makes routing decisions based on paths, network policies, and rulesets.

Question 13

What is a Link-Local IPv6 address and how does it start?

Accepted Answer

A Link-Local IPv6 address is automatically configured on all IPv6 interfaces and is used for communication only on the local link (segment). It starts with `FE80::/10`.

Question 14

What is the difference between a physical and a logical network topology?

Accepted Answer

-   **Physical Topology:** Describes the physical layout of network devices and cabling (e.g., star, mesh, bus).
-   **Logical Topology:** Describes how data flows through the network, independent of the physical arrangement (e.g., Ethernet uses a logical bus, even if physically a star).

Question 15

Which IEEE 802.11 standard introduced the 5 GHz frequency band and higher speeds than 802.11b/g?

Accepted Answer

IEEE `802.11a` introduced the 5 GHz band, offering speeds up to 54 Mbps. `802.11n` and `802.11ac` later significantly improved speeds in both 2.4 GHz and 5 GHz bands.

Question 16

What is the purpose of a DHCP server in a network?

Accepted Answer

A DHCP (Dynamic Host Configuration Protocol) server automatically assigns IP addresses, subnet masks, default gateways, and DNS server information to client devices on a network, simplifying network administration.

Question 17

What is the function of a network switch at the OSI model's Data Link Layer?

Accepted Answer

A network switch operates at Layer 2 (Data Link Layer) and forwards frames based on MAC addresses. It learns MAC addresses and creates a MAC address table to efficiently send traffic only to the intended destination port, reducing collisions.

Question 18

How many usable host IP addresses are available in a `/28` IPv4 subnet?

Accepted Answer

A `/28` subnet means 28 network bits, leaving $32 - 28 = 4$ host bits.
Number of total IP addresses = $2^4 = 16$.
Number of usable host IP addresses = $2^4 - 2 = 14$ (subtracting network and broadcast addresses).

Question 19

What is the primary difference between TCP and UDP?

Accepted Answer

-   **TCP (Transmission Control Protocol):** Connection-oriented, reliable, ensures ordered delivery, error checking, flow control, and congestion control.
-   **UDP (User Datagram Protocol):** Connectionless, unreliable, faster, no guaranteed delivery or ordering, minimal overhead.

Question 20

What is the role of a firewall in network security?

Accepted Answer

A firewall is a network security system that monitors and controls incoming and outgoing network traffic based on predetermined security rules. It establishes a barrier between a trusted internal network and untrusted external networks (like the internet).

Question 21

Explain the concept of 'default gateway.'

Accepted Answer

The default gateway is the IP address of the router on the local network that devices use to send traffic to destinations outside of their local subnet. Without a default gateway, a device can only communicate with other devices on its own local network segment.

Question 22

What is the purpose of the `ipconfig` (Windows) or `ifconfig` (Linux) command?

Accepted Answer

These commands display the current TCP/IP network configuration of a device, including IP address, subnet mask, default gateway, and DNS servers. `ipconfig /all` provides more detailed information.

Question 23

Which wireless standard is also known as Wi-Fi 6 and operates in both 2.4 GHz and 5 GHz bands, offering higher efficiency and speed?

Accepted Answer

IEEE `802.11ax` is known as Wi-Fi 6. It improves performance in dense environments and offers higher throughput and better power efficiency compared to previous standards.

Question 24

What is the function of the Presentation Layer (Layer 6) in the OSI model?

Accepted Answer

The Presentation Layer is responsible for data formatting, encryption, decryption, and compression. It ensures that data is in a format that the Application Layer can understand, acting as a translator between application and network formats.

Question 25

What is the main characteristic of a Mesh topology?

Accepted Answer

In a Mesh topology, every device is connected directly to every other device. This provides high redundancy and fault tolerance, as there are multiple paths for data, but it is expensive and complex to implement for large networks.

CompTIA Network+ (N10-008) - Networking Infrastructure & Protocols

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