On Fri, Feb 28, 2003 at 04:27:00PM -0500, Jeremy Faulkner wrote:
> On Fri, Feb 28, 2003 at 08:23:35PM +0100, Cliff Sarginson wrote:
> > On Thu, Feb 27, 2003 at 11:37:19PM -0000, Chris Phillips wrote:
> > > Aaron wrote: -
> > > I have a 3Com 3c900-Combo and ifconfig is reporting that it was in
> > > half-duplex mode, so I booted up my 3com dos utility book disk and
> > > checked and it was at half-duplex so I changed it to full.  ifconfig is
> > > still reporting it being half-duplex.  Do I need to reinstall the driver
> > > or something? How would I go about it?
> > > 
> > > Chris Phillips wrote:
> > > > Is it plugged into a hub or a switch?
> > > > A hub will only do half duplex.
> > > > A switch will do full duplex.
> > > > Worth mentioning...
> > > 
> > I don't know what the problem is but I do not think what you say is
> > correct. A hub can do full duplex, at least in my previous experience.
> A hub most certainly can not run full duplex. In order to run at full duplex 
> the tx and rx lines have to be separate.
> A hub is simply connecting all of the tx and rx lines in the ethernet cable 
> together w/ some amplification. Since all of the tx and rx lines are connected
> a packet transmitted from one machine will be received by all machines on
> the network.
> A switch can do full duplex because each port is essentially its own nic
> card. The switch segments the network and only traffic that needs to go
> through a specific segment will go to that segment. This division of 
> traffic is decided based on the mac address of the destination.
Well, that is true as far as it goes, but there are a few other
considerations being skated over here with regard to switches.
Well, before I started using switches my eyes must have been deceiving
me, because I built a small hub-based network, which was most definitely
running full duplex. So it either must have been some kind of super-hub
..:) or my eyes deceived me, or one of us is wrong. Or perhaps it was a
switch in a box marked hub. Or maybe the O/S was lying.

Well I don't have the device anymore, so I can't try it out.

This argument has been on this list once before btw, a long time ago, I
don't think I participated in it, but I do recall dissent on this very
topic...even among experts.

Still I am not an electrical engineer, I only believe what I see with my
own eyes :).


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