iBGP rule: A router adds its AS number to a route’s AS_PATH only when the route is sent to an EBGP neighbor. The AS number is not added to routes sent to an IBGP neighbor. Why we need full-mesh in iBGP: If we have RTR1–>RTR2–>RTR3 and iBGP peering is between RTR1 and RTR3 logically, the control plane…

SNMP: https://www.youtube.com/watch?v=HXu0Ifj0oWU SNMP components: SNMP Versions: SNMP message types: gMNI https://www.youtube.com/watch?v=psj4KeCWuOc

At a very high level, the operation of OSPF is easily explained: Hello packets are exchanged between neighbors as keepalives, and LSAs are retransmitted every 30 minutes. If the network topology is stable, no other activity should occur. Whenever a router sends a Hello, it includes in the packet the Router IDs of all neighbors…

CAM Table Vs FIB table: CAM table contains MAC address, egress port and vlan. Whereas, FIB table contains IP address, next-hop IP address, next-hop MAC address, Egress port. We use FIB and CAM Table in conjuction in multi-layer hardware based switching. Hardware based switching is always fast. Exceptions: Packets like ARP, IP packets which needs…

Single mode Vs multi-mode fiber: Single-Mode Fiber (SMF): Multi-Mode Fiber (MMF): Choose single-mode fiber for long-distance communication and multi-mode fiber for short-distance, high-bandwidth connections within data centers or buildings. Transceivers: an optical transceiver is a module that converts electrical signals into optical signals and vice versa, allowing data to be transmitted over fiber optic cables.…

GRE tunnel use-cases: GRE tunnels: Main components: GRE Packet: (transport protocol+GRE header)(encapsulate(Original Payload + passenger protocol) Configuration: See below scenario: R1:interface Tunnel100tunnel mode greip address 102.1.1.1 255.255.255.0ipv6 enable                     tunnel source Loopback0           tunnel destination 2.2.2.2 R2:interface Tunnel100tunnel mode greip address 102.1.1.2 255.255.255.0ipv6 enable                     tunnel source Loopback0           tunnel destination 1.1.1.1 Please note that 1.1.1.1 and 2.2.2.2 should be reachable from each…

The terms “kernel” and “operating system” (OS) are sometimes used interchangeably, but they refer to different components of the software that manages a computer. Here’s a detailed explanation of each: Kernel: The kernel is the core component of an operating system. It acts as the bridge between applications and the actual data processing done at…

What is a process? https://www.youtube.com/watch?v=4rLW7zg21gI https://www.youtube.com/watch?v=ls5cGi12kGw&list=PLtK75qxsQaMKLUENMaPlD_O2qS8ZBGjuy A process is program in execution. So what is a program ?: A program is an executable program. A program contains code or set of processor instructions which are stored as a file on disk. CPU has a program counter. Program is loaded into the memory and then program…

Service: A service is program which runs in the background. It answers to the requests etc. For instance, the “web service” might be provided by an httpd daemon like Apache or Nginx. Daemon:  a daemon is a type of program that runs in the background, and a service is the functionality that is provided to the system…

To check which users are logged in, we can use “w” command: To check users history who logged in: List all users: Create and delete users: