Catalog / Networking Fundamentals Cheatsheet
Networking Fundamentals Cheatsheet
A comprehensive cheat sheet covering essential networking concepts, protocols, and tools. Ideal for students, network administrators, and software developers looking to grasp the fundamentals of computer networks.
Network Fundamentals
Network Types
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PAN (Personal Area Network) |
Small network for personal devices, e.g., Bluetooth connection between a phone and headset. |
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LAN (Local Area Network) |
Network within a limited area, such as a home, school, or office. Ethernet and Wi-Fi are common technologies. |
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MAN (Metropolitan Area Network) |
Larger network spanning a city or metropolitan area. Connects multiple LANs together. |
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WAN (Wide Area Network) |
Network covering a large geographical area, such as the internet. Connects multiple LANs and MANs. |
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VLAN (Virtual LAN) |
Logically separate networks within a physical network. Improves security and network management. |
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SAN (Storage Area Network) |
A dedicated high-speed network connecting servers to storage devices, providing block-level access to data. |
Network Topologies
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Bus Topology |
All devices connected to a single cable. Simple but vulnerable; a break in the cable disrupts the entire network. |
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Star Topology |
All devices connected to a central hub or switch. More robust than bus, but the central device is a single point of failure. |
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Ring Topology |
Devices connected in a circular fashion. Data travels in one direction. Failure of one device can disrupt the network. |
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Mesh Topology |
Each device is connected to multiple other devices. Highly redundant but expensive to implement. |
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Tree Topology |
Combines features of bus and star topologies. Hierarchical structure. |
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Hybrid Topology |
A combination of two or more different topologies. Offers flexibility and customization. |
Key Networking Devices
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Hub |
Simple device that broadcasts data to all connected devices. Operates at Layer 1 (Physical Layer). |
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Switch |
Forwards data only to the intended recipient based on MAC address. Operates at Layer 2 (Data Link Layer). |
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Router |
Forwards data between different networks based on IP address. Operates at Layer 3 (Network Layer). |
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Firewall |
Security device that controls network traffic based on predefined rules. Can operate at multiple layers. |
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Wireless Access Point (WAP) |
Allows wireless devices to connect to a wired network. Typically operates at Layer 2. |
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Load Balancer |
Distributes network traffic across multiple servers to optimize performance and availability. |
OSI and TCP/IP Models
OSI Model Layers
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Layer 7: Application |
Provides network services to applications (e.g., HTTP, SMTP, FTP). |
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Layer 6: Presentation |
Handles data formatting, encryption, and decryption. |
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Layer 5: Session |
Manages connections between applications. |
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Layer 4: Transport |
Provides reliable or unreliable data delivery (e.g., TCP, UDP). |
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Layer 3: Network |
Handles routing of data packets (e.g., IP). |
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Layer 2: Data Link |
Provides error-free transmission of data frames (e.g., Ethernet). |
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Layer 1: Physical |
Defines physical characteristics of the network (e.g., cables, connectors). |
TCP/IP Model Layers
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Layer 4: Application |
Combines the functions of the OSI Application, Presentation, and Session layers. (e.g., HTTP, SMTP, DNS). |
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Layer 3: Transport |
Provides reliable or unreliable data delivery (e.g., TCP, UDP). |
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Layer 2: Internet |
Handles routing of data packets (e.g., IP). |
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Layer 1: Network Access |
Combines the functions of the OSI Data Link and Physical layers (e.g., Ethernet, Wi-Fi). |
Key Differences
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The OSI model is a conceptual model, while TCP/IP is a practical implementation. |
IP Addressing and Subnetting
IP Address Classes
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Class A |
1.0.0.0 - 126.0.0.0 |
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Class B |
128.0.0.0 - 191.255.0.0 |
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Class C |
192.0.0.0 - 223.255.255.0 |
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Class D |
224.0.0.0 - 239.255.255.255 |
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Class E |
240.0.0.0 - 255.255.255.254 |
Private IP Addresses
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10.0.0.0 - 10.255.255.255 (10.0.0.0/8) |
Subnetting Basics
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Subnet Mask |
A 32-bit number that separates the network and host portions of an IP address. Indicates the number of bits used for the network address. |
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CIDR Notation |
Shorthand representation of a subnet mask. |
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Subnetting Process |
Involves borrowing bits from the host portion to create subnets. This allows a single network to be divided into smaller, more manageable networks. |
Common Networking Protocols
Transport Layer Protocols
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TCP (Transmission Control Protocol) |
Connection-oriented protocol that provides reliable, ordered, and error-checked delivery of data. Used for applications like HTTP, SMTP, and FTP. |
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UDP (User Datagram Protocol) |
Connectionless protocol that provides fast but unreliable delivery of data. Used for applications like DNS, VoIP, and streaming. |
Application Layer Protocols
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HTTP (Hypertext Transfer Protocol) |
Used for transferring web pages and other content between web servers and browsers. Port 80 (default). |
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HTTPS (HTTP Secure) |
Secure version of HTTP that uses SSL/TLS encryption. Port 443 (default). |
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DNS (Domain Name System) |
Translates domain names to IP addresses. Port 53 (default). |
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SMTP (Simple Mail Transfer Protocol) |
Used for sending email. Port 25 (default). |
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POP3 (Post Office Protocol version 3) |
Used for retrieving email from a mail server. Port 110 (default). |
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IMAP (Internet Message Access Protocol) |
Used for retrieving and managing email on a mail server. Port 143 (default). |
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FTP (File Transfer Protocol) |
Used for transferring files between computers. Ports 20 and 21 (default). |
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SSH (Secure Shell) |
Used for secure remote access to a computer. Port 22 (default). |