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Differences between a hub and a switch

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Advanced Member level 1
Jul 1, 2004
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Hey guys i have this question?

Hub does broadcast when it is connected to a network when request is sent each and everytime as it doesnt have a MAC table.. but switch does have a MAC table so that it broadcasts the first time and then does only uni-cast..

I want to to know the reason why HUB does it broadcast each and everytime.. why cant it have a inbuilt MAC table.. is there any specific reason for the same?

When do we use passive hub..bcoz the active HUB has a clear advantage over passive hub..

which is faster? a HUB or a switch?

please help me out!

with regards,

advantage of switch over hub

why cant it have a inbuilt MAC table

Cost. Processor and RAM cost money.

When do we use passive hub

We usually don't. Ethernet switches are now cheap enough that people buy switches instead of hubs.

advantages of switches over hubs

well in that case.. switch has to be costlier than HUB.. but HUB is always expensive.. could you explain a typical scenarino where HUB and switch is used..

i know switch and HUB can be used to connect DTE and DCE..but one specific reason why HUB doesnt have a MAC table (reason why it does broadcast)? is it a design flaw? so the next better version of a the HUB is switch?

(remeber - HUB is layer 1 of OSI and switch is layer 2 of OSI)

why do companies use switches over hubs

hi arun,
with time the requirment of market is becoming high and high....

first broadcasting then swicth (due to bigger networks) then VLAN then QOS then routing ---are added into the products....

from layer 1 to lyr2 then upto layer 4, it can work..

MAC table is now a days common in Eternet chips...
for different purpose different feature are added to make a product more specific for specific use..

and about the price...
its market again...peripeheral chips of motherboard are expensive then mother board itself...

switch over hub

HUB is always expensive.

I havn't looked reccently but three years ago switches were much more expensive than hubs.

If hubs are now more expensive then, as tom_hanks says, it is because they are rare, few people buy them so manufacturers don't make hubs anymore.

i know switch and HUB can be used to connect DTE and DCE

DTE and DCE are serial port concepts. At the ethernet level every host device is the same, ethernet does not care which device is the master.

why we use switch rather than hub ?

thanks throwaway and tom_hanks.. :) ehe ive added these points to my research..

with regards,

how to make switch to hub

nowadays only switches are used


advantages of swithces and hubs

why hubs forward always frames?
because it is a layer 1 decice,dummy device, donot know any about layer 2 protocols, it just repeats the signal and output it on all the ports again, the ports are electrically shared

advantage of using switches rather than hubs

a 10/100 switch and 10/100 hub have the same port speed, but the switch produces less overall backplane traffic than a hub does since it "learns" where devices are and directs traffic to the destination device instead of sending it to all devices that are connected. Therefore with multiple devices a switch will perform better.

It was not a design flaw when hubs were made. No one thought of directing traffic since most people weren't sending over huge amounts of data accross networks so congestion was never a problem until networks started getting larger and the amount of data being shared got bigger.

Switches are the standard nowadays. Most companies no longer make or support hubs and the switches that they do make are very affordable.

+why use hub instead of switch

i think one advantage of switch over hub is : it 's secure because hub always broadcast packets

why are switches used instead of hubs

secure due to broadcasting? but there is always loss in b/w when it does the broadcasting eacha nd everytime...we need to compensate it with an external power supply...

data speed of switch over hub

Back in one piece.
hubs is dumb devices, it don't split the broadcast domain;that means it recieves data in any port and broadcasts it back to the whole other ports.
Every MAC must wait for his turn(half duplex) by using means of Token Ring Protocols.Hubs don't split the collision domain also.
The don't split criterion of hubs leads to bandwidth loss and collisions.

switches is smarter than hubs it tracks port MAC addresses by means of tables,it splits the broadcast domain(Ethernet devices); a MAC which didn't ask for data won't recieve it and a MAC which asked for data won't recieve data it never requested.that leaves the bandwidth optimized.Switches also,split the collision domain ( CSMA\CD protocols) no packets collide , no data lost.
at last switches is more smart ,effictive, faster and nowadays cheap than hubs.

mac table for multiple connected switches

i think one advantage of switch over hub is : it 's secure because hub always broadcast packets

Both hubs and switches are insecure when used to carry unencrypted data. Switches are just slightly less insecure. Just generate enough random arp querys and reply to fill the switches arp tables and see them go back to behaving like hubs.

we need to compensate it with an external power supply...

Both ethernet switches and ethernet hubs require external power.

why hubs is prefered than switches

Hub is realy much more slower than a switch. I large scale netwroks, using hubs is not good where switches are much more prefered but this is on the account of price.

why should i use switch over hub ?

Hub is using Collision Sense Multiple Access / Collision Detection (CSMA/CD) to perform multiple access for a group of hosts within the LAN. Each collision will cause a backoff where re-generating a delay to perform data re-send. instead, switch is keep updating a MAC table relative to the appropriate port in the switch. So, it is no CSMA/CD in switch and collision backoff is eliminated in switch technology. Hence, the switch is faster than hub.

hub mac table

So, it is no CSMA/CD in switch and collision backoff is eliminated in switch technology.

thx Cawan,
i missed it up.

how to view the mac table of a switch

arunragavan said:
which is faster? a HUB or a switch? arun

b/c it is efficient in the sense that it decides instantly to send data to its ports ... rather than broadcasting..

in Swictches, all ports got same data HUB they distribute data among ports...


when to use a hub instead of switch

can any one explain me what is ETHERNET and how it is used to send data through OFCs.
even tell me what is IP address
please refer me a book for mobile communications which has all basics.
please do help me

what is the advantage of switch over hub

hub contributes to spread the data to computer network at limited speed, however, switch spreads to each computer at limited speed, that's why may be it has a MAC table...

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