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I'm sneeking around online store for used stock of hubs, routers and switches for a project I have to build a network infrastructure.

So far, I have bought:

  1. 1x Cisco 2514 Router;
  2. 5x Cisco Serial Transceivers;
  3. 1x 24-port Cisco Catalyst switch.

I have souvenirs of having seen switches and hubs connected altogether, and remember that there is an advantage of some sort using such architecture, but I don't remember correctly, it's quite fuzzy in my mind as I am no network administrator, but a system developer.

I know that a switch builds itself a table of something to map the different connections, but can't remember excatly what it is. So my question is the following:

What is the difference between a hub and a switch?

Any answer is appreciated!

Thanks! =)

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This kind of information is all over the internet man.. – voodooo Jan 21 '11 at 17:55
@voodooo: Thanks for telling me! I absolutely didn't think about it... And seriously, one's explaning to another is often better than articles. – Will Marcouiller Jan 21 '11 at 17:58
Hint: hubs retransmit traffic to all ports. – voodooo Jan 21 '11 at 18:03
up vote 3 down vote accepted

Hubs are dumb.

But seriously, Read this.

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+1 Nice article that I easily understood! Thanks! =) – Will Marcouiller Jan 21 '11 at 18:11

A hub uses no logic to determine what to do with an incoming packet, it is simply blasted out all other ports once it is received. Conversely a switch uses layer 2 routing to determine the correct logical path by keeping a record of what hosts have communicated in the past (ARP tables).

Hubs are known for causing network congestion due to the increased overhead and Ethernet collisions.

Friends don't let friends buy hubs.

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lol, thankfully they're pretty tough to buy nowadays. – gravyface Jan 21 '11 at 18:01
+1 Your explanation is very good! You helped me. – Will Marcouiller Jan 21 '11 at 18:10
ARP doesn't really have much to do with switching. ARP tables map IP addresses onto MAC addresses. Often ARP is where the switch learns where a given MAC address is connected, but it by no means has to be. – Flexo Jan 21 '11 at 18:16

Old style passive hubs broadcasted all packets to all ports. These are no longer used and no longer available. They were later replaced by fasthubs and whatnot. The word Hub vs Switch is only a marketing choice.

Expensive switches have layer3 (IP) filtering, VLANs and HTTP interfaces. No need to get one though if $20 gigabit hub is enough.

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+1 Thanks for the information about the layers. =) – Will Marcouiller Jan 21 '11 at 18:04

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