Computer Networking Basics Flashcards

Question 1

What is a computer network, in its simplest form?

Accepted Answer

A computer network is two or more devices connected so they can share data, resources, or services. The connection may use cables, radio signals, or other media. Devices called nodes are any equipment that sends, receives, or forwards data on the network. Networks range from two linked laptops to the global internet.

Question 2

What is the difference between a host and a node?

Accepted Answer

Every host is a node, but not every node is a host. A host is an end device, such as a laptop, phone, or web server, that runs applications for people or other programs. A node is any device on the network that can send, receive, or forward data, including routers and switches.

Question 3

What is a packet, and why is data split into packets?

Accepted Answer

A packet is a unit of data with a header carrying addressing and control information, followed by the payload. Splitting data into packets lets many conversations share the same links. If a packet is lost or damaged, only that piece may need to be resent.

Question 4

What do bandwidth and latency measure, and how do they differ?

Accepted Answer

Bandwidth is the maximum amount of data that can pass through a link in a given time, usually expressed in bits per second. Latency is the delay between sending data and its arrival, measured in time. A connection can have high bandwidth yet still feel slow if its latency is high.

Question 5

What is a protocol in computer networking, and why is it needed?

Accepted Answer

A protocol is an agreed set of rules that defines how devices format, send, receive, and interpret messages. Without shared protocols, two devices built by different manufacturers could not understand each other. Protocols specify things like message structure, addressing, error handling, and the order of exchanges.

Question 6

What is the difference between a LAN and a WAN?

Accepted Answer

A local area network, or LAN, covers a limited area such as a home, office, or single building. A wide area network, or WAN, spans a larger geographic area, such as a city, country, or the connections between distant offices. The internet is the largest example of a WAN.

Question 7

What is a router, and how does it differ from a switch?

Accepted Answer

A router forwards packets between different networks, using IP addresses to choose the best path toward a destination. A switch connects devices within the same local network and forwards frames based on hardware addresses. In a typical home, one device often combines both roles along with wireless access.

Question 8

What is a hub, and why are switches used more often today?

Accepted Answer

A hub is a simple device that repeats every incoming signal to all of its ports, so all connected devices share the same collision domain. A switch learns which device is on each port and sends frames only to the port that needs them. This reduces unnecessary traffic.

Question 9

What is the purpose of a layered network model?

Accepted Answer

A layered network model divides communication into stacked functions, so each layer handles one job and relies on the layers below it. This separation lets engineers change one technology, such as the type of cable, without rewriting software at higher layers. The two most widely taught models are OSI and TCP/IP.

Question 10

What are the seven layers of the OSI model, from top to bottom?

Accepted Answer

From top to bottom, the OSI model lists application, presentation, session, transport, network, data link, and physical layers. A common memory aid is All People Seem To Need Data Processing, read from the top down. Each layer provides services to the layer above and uses services from the layer below.

Question 11

How does the TCP/IP model compare with the OSI model?

Accepted Answer

The TCP/IP model is a practical four layer design that underlies the internet, while the OSI model is a seven layer reference model. TCP/IP combines the application, presentation, and session layers into one application layer, and combines data link and physical into a network access layer.

Question 12

What is encapsulation, and how does it work as data moves down a stack?

Accepted Answer

Encapsulation is the process of wrapping data from a higher layer inside a header and sometimes a trailer added by each lower layer. As data moves down the stack, each layer adds its control information to the payload it received. The receiving device removes these headers in reverse order, a process called decapsulation.

Question 13

Which layer is responsible for logical addressing and routing between networks?

Accepted Answer

The network layer, which is layer 3 in the OSI model, is responsible for logical addressing and routing packets between networks. Protocols such as IP operate at this layer. Routers work here, examining destination addresses to decide which path a packet should take next.

Question 14

Which layer handles end to end delivery, reliability, and port numbers?

Accepted Answer

The transport layer handles end to end communication between application processes, using port numbers to direct data to the correct program. TCP provides reliable, ordered delivery, while UDP offers faster, connectionless delivery without those guarantees. This layer is layer 4 in the OSI model.

Question 15

What does the data link layer do, and what kind of address does it use?

Accepted Answer

The data link layer moves frames between devices on the same local network segment and detects certain transmission errors. It uses MAC addresses, which are hardware addresses assigned to network interface cards. Ethernet and Wi-Fi operate at this layer in the OSI model.

Question 16

What is the role of the physical layer in network communication?

Accepted Answer

The physical layer transmits raw bits over a medium, converting data into electrical, optical, or radio signals. It defines things like cable types, voltage levels, connector shapes, and radio frequencies. This layer does not interpret the meaning of the bits, which is left to higher layers.

Question 17

What is an IP address, and what does it identify?

Accepted Answer

An IP address is a numerical label assigned to a network interface so packets can be addressed and routed. It identifies where a device attaches to a network. IPv4 addresses are 32 bits long, usually written as four decimal numbers separated by periods.

Question 18

What is the difference between IPv4 and IPv6?

Accepted Answer

IPv4 uses 32 bit addresses, which gives roughly four billion unique values, while IPv6 uses 128 bit addresses for a vastly larger address space. IPv6 was created largely because IPv4 addresses became scarce. Both protocols route packets, but they are not directly compatible with each other.

Question 19

What is a subnet mask, and what does it do?

Accepted Answer

A subnet mask is a 32 bit pattern that separates an IPv4 address into a network portion and a host portion. Devices use the mask to decide whether a destination is on the same local subnet or must be reached through a router.

Question 20

How is CIDR notation written, and what does the number after the slash mean?

Accepted Answer

CIDR notation writes an IP address followed by a slash and a number, such as 192.168.1.0/24. The number after the slash states how many leading bits make up the network portion. In this example, the first 24 bits identify the network, leaving 8 bits for host addresses.

Question 21

How many usable host addresses does a /24 IPv4 subnet provide?

Accepted Answer

A /24 IPv4 subnet provides 254 usable host addresses. It contains 256 total addresses, but two are reserved: the first address identifies the network itself, and the last address serves as the broadcast address. The usable count is always the total minus two for ordinary subnets.

Question 22

What are private IP address ranges, and why are they used?

Accepted Answer

Private IPv4 address ranges are blocks reserved for use inside local networks, including 10.0.0.0 through 10.255.255.255, 172.16.0.0 through 172.31.255.255, and 192.168.0.0 through 192.168.255.255. They are not routed on the public internet, so many organizations can reuse them. Network address translation allows many private devices to share one public address.

Question 23

What is DHCP, and what does it provide to a client device?

Accepted Answer

DHCP, the Dynamic Host Configuration Protocol, automatically assigns IP configuration to client devices when they join a network. A DHCP server typically provides an IP address, a subnet mask, a default gateway, and DNS server addresses. Addresses are leased for a set time, so unused addresses can be reassigned.

Question 24

What is a default gateway, and what happens when a destination is outside the local subnet?

Accepted Answer

A default gateway is the router address that a host sends traffic to when the destination is not on its own subnet. The host forwards the packet to that router, which decides where to send it next. Without a correct default gateway, a device can reach local peers but not remote networks.

Question 25

What is the difference between a port number and an IP address?

Accepted Answer

An IP address identifies which device a packet should reach, while a port number identifies which application or service on that device should receive it. Port numbers range from 0 to 65535. Web servers commonly listen on port 80 for HTTP and port 443 for HTTPS.

Question 26

How does TCP establish a connection before sending data?

Accepted Answer

TCP uses a three step handshake. The client sends a SYN segment, the server replies with a SYN ACK, and the client answers with an ACK. Once this exchange completes, both sides agree on starting sequence numbers and data can flow reliably.

Question 27

When is UDP a better choice than TCP?

Accepted Answer

UDP is often preferred when speed and low overhead matter more than guaranteed delivery, such as in live video, voice calls, and online games. Because it has no handshake or retransmission, a lost packet is not resent, so the application must tolerate or recover from loss itself.

Question 28

What does DNS do, and why does a browser need it?

Accepted Answer

DNS, the Domain Name System, translates human readable domain names such as example.com into IP addresses that networks can route. A browser needs this step because it must know the numerical address of the server before it can open a connection. DNS responses are often cached so repeated lookups are faster.

Question 29

What happens during an HTTP request and response cycle?

Accepted Answer

A client sends an HTTP request containing a method, such as GET, a path, and headers describing what it wants. The server processes that request and returns an HTTP response, which includes a status code, headers, and usually a body such as HTML. HTTP is stateless, so each request is handled independently.

Question 30

What is the difference between HTTP and HTTPS?

Accepted Answer

HTTP sends requests and responses in plain form, so anyone able to observe the traffic could read it. HTTPS wraps the same HTTP messages in TLS encryption, which protects data confidentiality and lets clients verify the server identity through certificates. The application behavior is the same, and the security layer is what differs.

Question 31

How does a recursive DNS resolver find an answer for a name it has not cached?

Accepted Answer

A recursive resolver asks other DNS servers on the client's behalf, starting with a root server, then a top level domain server, then the authoritative server for the domain. The resolver stores the final result for the record's time to live, then returns it to the client.

Question 32

What is flow control in TCP, and why is it needed?

Accepted Answer

Flow control lets a receiver tell the sender how much data it can accept, so a fast sender does not overwhelm a slow receiver. TCP does this with a window size advertised in each acknowledgment. Without flow control, buffers would overflow and packets would be dropped and resent unnecessarily.

Question 33

What is a firewall, and what does it typically do?

Accepted Answer

A firewall is a security control that permits or blocks network traffic according to defined rules. It commonly filters packets by source and destination address, port, and protocol. Firewalls can run on dedicated hardware, on a host computer, or inside a cloud service.

Question 34

What is network address translation, and why do home routers use it?

Accepted Answer

Network address translation, or NAT, rewrites the addresses in packets so many private devices can share one public IP address. The router keeps a table that maps each outbound connection to the correct internal device when replies return. Home routers rely on it to connect a household through one internet address.

Question 35

What is the purpose of encryption in network communication?

Accepted Answer

Encryption transforms readable data into scrambled ciphertext that only holders of the correct key can decode. It protects confidentiality, so an eavesdropper who captures packets cannot read their contents. Encryption alone does not guarantee that data was unchanged, so it is often combined with integrity checks.

Question 36

What does the ping command test, and what does it report?

Accepted Answer

The ping command tests basic reachability by sending ICMP echo request messages to a target and waiting for echo replies. It reports whether replies arrived and how long the round trip took. A failed ping does not always mean the host is down, since firewalls may block ICMP.

Question 37

What does traceroute show, and how is it useful?

Accepted Answer

Traceroute shows the sequence of routers a packet passes through on its way to a destination, along with the delay at each hop. It works by sending packets with increasing time to live values, so each router along the path reports itself when the value expires.

Question 38

What is the difference between a stateful firewall and a stateless packet filter?

Accepted Answer

A stateless packet filter evaluates each packet on its own, using only the rules and the packet's header fields. A stateful firewall tracks the state of connections, so it can allow return traffic that belongs to a connection initiated from inside the network.

Question 39

What is a VPN, and what does it protect against?

Accepted Answer

A virtual private network, or VPN, creates an encrypted tunnel between a device and another network across an untrusted network such as the public internet. It protects traffic from eavesdropping and tampering while it crosses networks outside your control. A VPN does not by itself protect a device from malware or guarantee anonymity.

Question 40

What is a systematic approach to troubleshooting a network connection problem?

Accepted Answer

A common method starts at the physical layer and works upward: check cables, link lights, and Wi-Fi signal first, then verify IP configuration, then test reachability of the local gateway, remote addresses, and finally names. Each step isolates whether a fault sits in hardware, addressing, routing, or name resolution.

Computer Networking Basics Flashcards

1Core Networking Concepts

2Layered Network Models

3IP Addressing and Subnetting

4Transport and Application Protocols

5Security and Troubleshooting Basics

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