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----------------------------------------------------------Permission is granted for the below article to forward,reprint, distribute, use for ezine, newsletter, website,offer as free bonus or part of a product for sale as longas no changes a Gone are those times when the companies and the organisations didn't need a hi-tech system to handle them. Owing to the considerable increase in the business sector and thus, an enormous increase in the complexity of the organisational struc
Routing and switching are twobasic activities in any network and 80% of network management andtroubleshooting involves these two. Routing is related to communication betweentwo different networks while switching is responsible for communication withina network. The two are explained below:Switching: Switches are basic part of any LAN. All the computersand other devices on the LAN need to be connected to the switch in order tocommunicate with each other. Switches operate at Layer 2 of OSI model i.e. theData Link Layer. That is why switches understand MAC addresses (48 bitburned-in address of the network interface card) and forward data on the basisof destination MAC address. Switch work in the following manner:In the beginning, the MAC tableof the switch is empty. This is the learning state of the switch in which itlistens to the network to build its MAC table. Let us assume that the switchreceives a frame from computer A meant for Computer B connected to ports 1 and2 of the switch respectively. Switch can read source and destination MACaddresses in the frame. It first stores the MAC address of the sender A againstits port 1. Now as the switch does not know on which port destination B isconnected, it will forward the frame on all its ports except for port 1 (theport connected to computer A). This is called flooding. All computers exceptB will reject the frame. When B will reply, the switch will store its MACaddress against port 2 and forward frame to A (its MAC already known). This wayswitch keeps building its MAC table and it is a dynamic process. Routing: Router operates at Network Layer (Layer 3) of the OSI modeland is responsible for routing data to other networks on the basis of IPaddresses. Like all the other computers and devices, the router is alsoconnected to the switch. Normally it acts as the default gateway and the datameant for other networks is automatically sent to the router. The router willuse static or dynamic routing to forward the packet to its destination network.In static routing, it has a static route defined in its routing table whichclearly specifies that a certain network is attached to which port of therouter. Whereas in dynamic routing, a routing protocol running on the routerdecides how to reach a certain network. Common routing protocols are RIP, IGRP,EIGRP, BGP and OSPF. The routing protocols decides the best path (in case multiplepaths exists) to reach the destination. The mechanism for deciding the bestpath is different for different protocols. But in the end, all these build arouting table in the router in which destination networks are mapped againstrouter ports. Routing protocols take care of network changes itself whilestatic routes need to be manually changed. In addition to routing, the routercan restrict access of certain users and certain destination on the basis of IPaddresses and the protocols being used. This is done through access lists.
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