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Working of a Networking Switch (for dummies)

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#1 Pinesh


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Posted 18 September 2016 - 12:36 AM

I have an academic question which i am unable to understand and thus unable to reply to students learnning ICT. 
We have a small ICT computer lab with a windows server + switch + 9 computers + Modem / Router for internet + Cyberoam Firewall ... as a LAN set up. We teach ICT to students in grade 8-9-10. 
Their textbook (of NETWORKING)  mentions "A switch is a more ‘intelligent’ device than a hub: if it receives a message, it checks who it is addressed to, and only sends it to that specific computer. Because of this, networks that use switches are more secure than those that use hubs". 
My confusion is during any LAN based working and LAN based data sharing or saving by students /  teachers - they personally select the path and folders and Switch does not really do the selection process of which computer is the data to be shared / saved / copied from / pasted etc. 
Even while using internet, the firewall checks the MAC ID and applies rules. 
Best to my knowledge, the switch only works as routing of data  - BUT - the textbook says it works intelligently and checks the recepient's MAC ID and sens data to that PC only. 
Thus my question is :- 
(1) In which real time activity does a Switch check MAC id of computer and routes data to that computer? 
1a) Is it related to any broadcast messages where certain recepients are selected? But here again the software would do the selection and routing. 
1b) Does this relate to any emails being downloaded? (But would not the email server do the routing?).
Can any network expert help me please for me to understand the above -  practically - as to - in which activity does a switch 'receive' a message and checks who it is addressed to ..... 
Thanks in advance for all the help. 
Pinesh Mehta 

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#2 Wand3r3r


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Posted 18 September 2016 - 10:57 AM

"networks that use switches are more secure than those that use hubs"


I can see why you are confused when you get that kind of information.  It is incorrect to use the term routing when talking layer 2 devices.  No routing takes place. Devices at this layer store and forward/selectively transfer data.


Q1: the difference between a hub and a switch is a switch keeps a mac address table on every port whereas a hub can't do that.  A hub would send the same data to all ports with the hope of the correct connected device would get the data.  A switch just send that data to the specific port via its mac table.


Q2: Broadcasts, by their very nature, go to all ports


Q3: "they personally select the path and folders"


"Does this relate to any emails being downloaded?"


you need to understand the OSI model.  What layer does a application [file sharing/email] work at vs the data link layer?

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