Rajat Handa

This video will help you to learn how DNS works

How TCP / IP works

How internet works, I found some video on you tube this will help you to visualize and learn this in better way

What happens if you've made changes to your router's configuration and something goes wrong? How can you get back to where you started? David Davis tells you about a command that helps you roll back changes while minimizing downtime. Have you ever made changes to your Cisco router or switch and then needed to remove them? There are several ways to do this, but which is the safest and easiest method? Rebooting the router or switch isn't the answer. In fact, a simple command is a much better bet. Let's say you're implementing some changes on a router that has a large configuration file. Maybe something distracted you when you were making the change, but the new feature doesn't work when you go to test it. You just want to back everything out and start from scratch. How can you do that? You have a couple of options. If you haven't saved the configuration yet, you can just reload the router. This will work, but you don't want to have to reload a production r...

10 Hot Skills for 2009 1. Business Skills Employment surveys have been telling us for a number of years that IT pros must possess business skills as well as technical expertise, and in a down economy IT folks who understand the business could be considered more valuable than those who don’t. A survey by CompTIA of 215,085 IT pros found that employers valued “interpersonal and communication” skills in addition to ‘strategic thinking” and “project management” know-how. The survey, which was conducted in 2007, found that 73% of respondents said they planned to upgrade their business skills within two years, with the majority studying for project management skills. 2. Programming Languages (C, C++, C#) Forget about programming jobs being outsourced, experts with C, C++ and C# skills “have emerged as a highly desired skill set, being cited as ‘in demand’ just as often as Business Intelligence and Enterprise Solutions skills,” according to the Veritude 2009 IT Outlook Report. Demand for soft...

Boder Gateway Protocol Message Type: Four different message types are used in BGP-4: • Open messages—Used to establish connections with peers. • Keepalives—Sent periodically between peers to maintain connections and verify paths held by the router sending the keepalive. These packets are sent unreliably. If the periodic timer is set to a value of 0, this equates to infinity, and no keepalives are sent. • Update messages—Contain paths to destination networks and the path attributes. Routes that are no longer available or withdrawn routes are included in updates. There is one path per update, requiring many updates for many paths. The information contained in the update includes the path attributes such as origin, Autonomous System path, neighbor, and inter-Autonomous System metric. • Notification—Used to inform the receiving router of errors.

Network Tools Traceroute : Traceroute transmits packets with small TTL values. Recall that the TTL (Time To Live) is an IP header field that is designed to prevent packets from running in loops. Every router that handles a packet subtracts one from the packet's TTL. If the TTL reaches zero, the packet has expired and is discarded. Traceroute depends on the common router practice of sending an ICMP Time Exceeded message, back to the sender when this occurs. By using small TTL values which quickly expire, traceroute causes routers along a packet's normal delivery path to generate these ICMP messages which identify the router. A TTL value of one should produce a message from the first router; a TTL value of two generates a message from the second; etc. In a typical traceroute session, a group of packets with TTL=1 are sent. A single router should respond, using the IP address of the interface it transmits the ICMP Timeout messages on, which should be the same as the interface it ...