[cisco-voip] 24 port switch question

[Norton, Mike]

If you completely fill the MAC table of a switch, you’ll “turn it into a hub” in the sense that it would start forwarding traffic out all ports. But you still wouldn’t have collisions, because the ports would still all be full duplex.

If all ports are full duplex, there is no amount of traffic that could cause collisions. Collisions can only occur on shared media and shared media can only be half duplex. With enough traffic, you’ll start getting dropped/delayed frames - but that’s not a collision.

At least, that’s my take on it.

--
Mike Norton
I.T. Support
Peace Wapiti School Division No. 76
Helpdesk: 780-831-3080
Direct: 780-831-3076

From: cisco-voip-bounces at puck.nether.net [mailto:cisco-voip-bounces at puck.nether.net] On Behalf Of Lelio Fulgenzi
Sent: September-29-10 6:07 PM
To: Matthew Ballard
Cc: cisco-voip at puck. net
Subject: Re: [cisco-voip] 24 port switch question

I recall a bug/exposure where one could turn a switch into a hub by flooding the switch with arp announcements or something like that.

…
Don't look at me, my iPod maid that spilling mistake.

On 2010-09-29, at 5:57 PM, Matthew Ballard <mballard at otis.edu<mailto:mballard at otis.edu>> wrote:
On a switch with all ports running full duplex, the collision domain is reduced down to the level of the individual port (which is one of the key benefits of a switch), so you should never see a collision if all ports are connected at full duplex to other switches and/or devices.

Beyond that, it depends on the switch, as you’ll hit either port capacity or forwarding limits of the switch before anything gets dropped.

Matthew Ballard
Network Manager
Otis College of Art and Design
mballard at otis.edu<mailto:mballard at otis.edu>


On 9/29/10 1:41 PM, "Robert Shearrill" <rshearri at uchicago.edu<mailto:rshearri at uchicago.edu>> wrote:
Hi,

Can some answer this question for me, or tell me where i can find the reading on this question? I have looked and can find it no where.

Question:

How many frames can pass through a 24-port switch simultaneouly, without causing a collision and with using full duplex used on all ports?

Thanks

Robert
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