Re: Maximum *Practical* Distance of CAT5e?

"Stuart Robinson" <Stuartr@xxxxxxxxxxxxx> wrote in message
news:memo.20051110203824.1580B@xxxxxxxxxxxxxxxxxxxxxxxx
> > I know that the official distance that CAT5e can run is 100 meters;
>
> For a link to fall within the definition of Cat5e that is indeed correct.
> And is also the distance limit in the Ethernet spec for 100Mbs and 1Gb
> Ethernet.
>
> There is however no specific length limit for 10Mbs UTP Ethernet and in a
> point to point link round trip delay times wont be an issue.

not true - the limit was 100m - but it says Cat3 or better.

in practice 10M will go a long way on good cable with good conditions - see
the separate post by Jeff Liebermann
>
> There is an attenuation and crosstalk test specified for 10Mbs Ethernet
> and if your using Cat5 cable that equates to somewhere near 180M to 190M
> of cable.

Agreed - but even that is conservative - i.e. it assumes cable that just
meets the Cat5 spec, and worst case combination of cabling practice, and
reciever sensitivity etc. The various versions of what is claimed to be "Cat
6" and "Cat 7" would give you more margin to play with.

there was a fair amount of slack built in to make everything reliable in the
real world - just think on how many patch leads get trodden on, how often
someone uses a different type of cable in a patch lead etc.
>
> However as others have suggested you must force either end of the link to
> 10Mbs, the auto negotiation process is not a qualative check on the speed
> capability of the cable.

Agreed. A relaible 2nd hand hub somewhere in the link may be an easy fix.

The old 3Com / Synoptics stuff seems to last forever....

if you must run a long way, then there are "long reach ethernet" products
designed to run up to 15 Mbps over several 100 m of poor quality cable
(phone wiring) - the cisco flavour is based on DSL type protocols. search
for LRE on their site if you want to go this way.
>
> Stuart.
--
Regards

stephen_hope@xxxxxxxxxxxx - replace xyz with ntl


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