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Re: fast ethernet limits

  • From: Stephen J. Wilcox
  • Date: Fri Jan 10 16:16:01 2003


On Fri, 10 Jan 2003, Douglas A. Dever wrote:

> 
> Previously, Steve Rude (steve@rudedogg.com) wrote:
> > 
> > Hi NANOG,
> > 
> > Could someone please help me with a fast ethernet problem I am having.  We 
> > have a POP in a 27 floor building, and have a rj45 run from the the bottom 
> > of the building (in the telco room) to the top of the building.  We have 
> > cisco switches on either end and we are seeing about 5-20% packet loss on 
> > the trunk.  
> > 
> > Are we running into a distance limitation of fast ethernet, or are we suffering 
> > from another problem?  I read that 328 feet is the limitation of fast 
> > ethernet. Is there anything short of getting a repeater for the cable run 
> > that I can do to boost the signal?
> 
> Well, when I don't have drawings or prints, I usually figure on 12 or 13ft
> per floor.  So, figure somewhere between 324 and 351 feet from 1st floor
> to the ceiling on 27.  For a run like this, you probably wanted to use fiber
> with media converters on each end.  (Assuming you're not running
> switches with 100BaseFX ports or a GBIC slot...)

Indeed altho depending on purpose bear in mind a repeater is just a hub or
switch, if you can fit one half way up you should solve your loss problems.

Yeah 328 is the alleged limit but it can go further usually, as another reader
said you need good connectors and cables tho. A more likely cause of trouble
for you in the ducting is interference if you're running alongside AC mains and
other data cables both of which will increase noise and reduce the limit even
more.

Steve





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