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Hub, Switched Hub, Switch..

Hi,

I haven't found much information to answer this question, so I thought I'd give it a shot here:

What is, if any, the difference between a _switched hub_ and a _switch_? I've heard and seen a number of suggestions, for example that a switched hub can switch between its segments, that it's just like a switch, that it's just like a switch but that you have to edit the MAC lookuptable yourself (it's static), that it can exchange traffic between 10/100 along its segments, and what not..

So, can someone please shed some light here? I would be really grateful.

I set this as a 150p question, hoping for a quality answer =)

Regards,

  Leo R. Lundgren
  E-mail: leo@finalresort.org
  Cellular: +46 (0)70 26 75 619
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rAWTAZ
Asked:
rAWTAZ
1 Solution
 
lrmooreCommented:
Here's the deal with a 10/100 "switch-hub":

each port is autosensing to 10 or 100Mb
All 10M ports are pooled into one "hub" (collision domain)
All 100M ports are pooled into one "hub"
The backplane acts as a switch between these two hubs.
Because each port is really part of a shared hub, you cannot use full-duplex.

On a true 10/100 switch, each and every port is an independent bridge port (collision domain) and switched on the backplane. Since each port is an independent and does not share the collision domain, full-duplex operation is possible.
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rAWTAZAuthor Commented:
Sounds reasonable.

I'm about to recieve a 10Mbit HP switching hub, of which I don't know the model. I think it has a 100Mbit uplink though. Anyhow, how would this "switch", since there are not two speeds on the ports, will it only switch between the uplink and the port segments?

/Leo
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lrmooreCommented:
Without the exact model number, it sounds like all the 10M ports are on one hub, with the switching only between the hub and the uplink...
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criemanCommented:
Switching can happen at 10Mbs or 100Mbs.
A hub forwards packets out all ports
A switched hub (or switch) Only sends the packet to the interface where the destination mac address resides.

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rAWTAZAuthor Commented:
lrmoore,

yeah, that's an option. it'll get a bit clearer when i get the equipment.

crieman,

do you mean that a switched hub and a switch are the same thing? i have the impression that a switched hub is somewhat of a "half"/not fully featured switch. anyhow, is that the case?

seems to me like i've gotten two different inputs on this, once again :))

/Leo
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lrmooreCommented:
I think crieman was simply explaining a bit more at the functional level of how a hub and a switch work.
A hub always has the same behavior, whether it is physically a group of ports on one "switching hub", or a stand-alone hub. All packets coming in one port are flooded to all other ports thus creating one collision domain.
A switch, on the other hand, will only forward packets to the particular port where the destination MAC address lives.
In a switched-hub, all 10Mb ports see all packets, but the 100Mb side does not see them unless the destination MAC address is in the 100Mb side and vice versa. You have two collision domains, with a switch between them.
In all cases, broadcasts get forwarded out all ports regardless of hub or switch so you still have one broadcast domain no matter how many switched ports or hubs you have.
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rcasteelCommented:
Also...some switched hubs have a fixed port configuration...ports 1-8 are on 1 channel of the switch and 9-16 are on another etc.

Some switched hubs are programable so you can choose  which ports are in each collision domain.

Some switched hubs are simply a hub that switches into the backbone or uplink port.

A switch can switch into any port while a switched hub groups ports together in some fashion and switches the entire group into another group.  Thwe actual way the ports are grouped varied from manufacturer to manufacturer and model to model.
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lrmooreCommented:
This question appears to be abandoned. I will allow one week before I close this question
with the following recommendation:

- points to lrmoore

if there is any objection to this recommendation then please post it here within 7 days.

thanks,

lrmoore@nw
EE Cleanup Volunteer
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rAWTAZAuthor Commented:
Hi,

Indeed, it's been quite abandoned for a while. The reason i haven't closed it myself is that I haven't felt 100% comfortable with the information gained from the comments.

However, I not to argue that people haven't done their best in trying to answer it.

In any case, I'll be happy to give lrmoore a bunch of points for his professional comments in this thread.

Regards,

  Leo R. Lundgren
  leo@finalresort.org
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