Layer 3 (Network Layer) – Responsible for routing packets between networksIPv4 packet = IPv4 header + payload 🔹 IPv4 Header Fields Field Bits Description Version 4 IP version: 4 for IPv4 (0100), 6 for IPv6 (0110) IHL (Internet Header Length) 4 Header size in 4-byte blocks. Min: 5 (20 bytes), Max: 15 (60 bytes) DSCP…
Default Behavior of Interfaces Device Interface Default When Device is Plugged In Switch No shutdown command Goes up/up automatically Router Has shutdown command Stays admin down/down, must be enabled manually 🟡 Switch Interfaces 🔴 Router Interfaces Interface Status Commands SW1# show ip interface brief // Summary (L1/L2) – works for routers/switches SW1# show interfaces status…
Layer 3 and IP IP Broadcast Binary Conversion Binary to Decimal Decimal to Binary Number Systems Base Description Binary Base-2 → powers of 2 Decimal Base-10 → powers of 10 Hexadecimal Base-16 → powers of 16 IPv4 Address Classes Class Binary Start Range Notes A 0xxxxxxx 1–126 0.0.0.0 reserved, 127.x.x.x is loopback B 10xxxxxx 128–191…
LAN Basics Data Encapsulation: PDUs Ethernet Frame Structure [ Preamble (7) | SFD (1) | Destination MAC (6) | Source MAC (6) | Type/Length (2) | Data | FCS (4) ] Ethernet Header (14 bytes) Preamble + SFD (not technically part of header) Ethernet Trailer (4 bytes) MAC Address (6 bytes) Hexadecimal and Decimal Quick…
CLI vs GUI Connecting via Console Port CLI Modes Configuration Files Two types: To save configuration: write write memory copy running-config startup-config Password Encryption Use enable secret instead of enable password (more secure) service password-encryption no service password-encryption enable secret 5 xxx # Type 5: MD5 encryption enable password 7 xxx # Type 7: Cisco…
A networking model provides structure and categories for both logical protocols and physical standards. A networking protocol is a set of rules that defines how devices and software should operate and communicate logically. OSI Model (Open Systems Interconnection) Adjacent-Layer vs Same-Layer Interaction Layer 7 – Application Layer 6 – Presentation Layer 5 – Session Upper…
After spending time with cloud platforms like Azure, AWS, and DigitalOcean — as well as Type 2 hypervisors (like VirtualBox) — I decided to try something new: a Type 1 hypervisor installed directly on hardware. My choice? The open-source, free, and powerful Proxmox VE (Virtual Environment). Here’s a step-by-step walkthrough of how I installed and…
Recently, I got a used Cisco 881 router that was already configured (asking for a login and password when it started). The previous owner didn’t remember the credentials, so I had to reset it to factory settings. It turned out to be more difficult than I thought — here’s what I learned. 👇 1️⃣ ROM…
Ethernet is a collection of network protocols and standards. When you hear Ethernet think of IEEE 802.3, which means transmission over cables (copper or fiber-optic).When you hear Wi-Fi think of IEEE 802.11, which means wireless transmission. Data Transmission Basics Ethernet Standards (Copper) Different IEEE standards define transmission speed and cable type. Speed Common Name IEEE…
A computer network is a digital telecommunications network that allows nodes to share resources. Common Devices in a Network Types of Firewalls Examples of Cisco Devices 📌 These are personal study notes. Please read the full disclaimer for more information.