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Setting Linux Host as a Router

 Setting up a Linux server as a router involves configuring the server to forward network traffic between different network interfaces. Here’s a step-by-step guide to achieve this: 1. Install and Configure Network Interfaces Ensure your server has at least two network interfaces: WAN (External Interface): Connected to the internet (e.g., eth0 ). LAN (Internal Interface): Connected to your internal network (e.g., eth1 ). Example Setup: eth0 : 192.168.1.2 (WAN, connected to your ISP or upstream router). eth1 : 10.0.0.1 (LAN, connected to your internal network switch or directly to other devices). 2. Configure IP Addressing Assign static IP addresses to your network interfaces. Edit the network configuration: sudo nano /etc/network/interfaces # WAN Interface (eth0) auto eth0 iface eth0 inet static   address 192.168.1.2   netmask 255.255.255.0   gateway 192.168.1.1 # Your upstream router or ISP gateway # LAN Interface (eth1) auto eth1 iface eth1 inet static   addr...
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IP Ranges

 IP addresses are divided into different ranges based on their purpose and usage. Here's a breakdown of the various IP ranges used for different scenarios: 1. Private IP Ranges Purpose: Used within private networks, such as home or corporate LANs. These IPs are not routable on the internet. Ranges: Defined by RFC 1918 Class A: 10.0.0.0 to 10.255.255.255 Subnet Mask: 255.0.0.0 or /8 Class B: 172.16.0.0 to 172.31.255.255 Subnet Mask: 255.240.0.0 or /12 Class C: 192.168.0.0 to 192.168.255.255 Subnet Mask: 255.255.0.0 or /16 Use Cases: Home routers, corporate LANs, Virtual Private Networks (VPNs). 2. Public IP Ranges Purpose: Used for communication over the internet. These IPs are routable and must be unique across the internet. Ranges: Any IP address not in the private ranges mentioned above is considered a public IP address. Examples: 8.8.8.8 (Google Public DNS) 192.0.2.0/24 (TEST-NET-1, reserved for documentation and examples) Public IPs are assigned by Internet A...
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K8 : Networking : Switches

 How does system A connect system B  What is a Switch ? A network switch is a fundamental device used in various scenarios to manage and direct data traffic within a network. Switches are crucial for building efficient and scalable networks, particularly in Local Area Networks (LANs). Here’s when and why you would use a network switch: 1. Connecting Multiple Devices within a Local Network (LAN) Scenario: In an office, home, or data center where multiple computers, printers, servers, and other devices need to communicate with each other. Purpose: A switch connects these devices to form a local network, allowing them to share resources like printers or access the internet through a single router. Function: The switch intelligently forwards data packets between devices on the same network, based on MAC addresses, without flooding all ports.
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