sundance-communications.com/forum Forums Wiring - Telecom Carriers - Trunks & Services Cabling Telephones Systems Wiring cat 5 existing or cat 6 rewire?

Often times the labour cost of sorting out and reusing old abandonned cable eceeds the cost of pulling new.

It depends on the job, for example, a large job I did a year ago...my customer bought a building and renovated it. The majority of the existing data cabling went to appropriate places for them. I had to add several drops because they put new offices in, but I was able to re-use a good amount of cabling.

I agree with Marv, if its not clearly labeled on both ends, I would'nt spend the time trying to sort it out. Pull new.

Sure, the Cat5 cable will probably work fine for gigabit, even though it isn't rated for it. Worst case scenario though, you could inherit a bunch of problems reusing cheap cable that was poorly installed between 10 and 20 years ago. And in that time, how many cables have been damaged during renovations, run alongside power, or chewed through by rodents? I'm in the 'pull new wire' camp.

I am sceptical about CAT5 cable's ability to consistently deliver gigabit. I believe that it's not worth the troubleshooting that will inevitably follow the bottlenecks and slowdowns.

Two things to keep in mind:

1. Cat5 is officially designated as "obsolete technology" by the EIA, and not part of the current Category specs.

2. The original Cat5 jack/plug wiring was supposed to accomodate a 100Mbit connection and used 2 pairs. Gigabit wiring uses all 4 pairs, with attendant xtalk requirements that are beyond what most Cat5 installations can provide.

sph, I would be interested on your feedback for this article:

https://www.flukenetworks.com/fnet/...icles/1000BASE-T+over+copper+cabling.htm

Anything before 1995 is going to be a crap shoot, but you can test for it and users are often surprised as to how well the link performs. It's not always happy news but you can test for it before ripping it out as in the case of a local hospital here where asbestos was used.

Adrian, in general I tend to agree with the article, although personally I would just rewire wherever possible. I understand there are extreme circumstances when pulling new wire is just not an option so you have to make do with the lower frequency cable.

One observation: we are talking about 2 different standards here - transmission and cabling. They are administered by 2 different bodies (IEEE and EIA). They don't work in lockstep, although they do try to keep in tandem. It is not at all unusual that the transmission standard was finalized before the cabling scheme that would properly accomodate it - actually it makes more sense, imo. Not having read the minutes of the relevant committees, I don't know whether gigabit-over-cat5 was a stopgap until the EIA could deliver the "proper" cable.

My understanding is that cat5e was a required spec because some cat5 cable did not meet the requirements of Gigabit. The cat5 spec was not tight enough and some cable manufacturers cut corners, making cable that barely met the cat5 spec and certainly didn't exceed it. Other manufacturers made cable that exceeded the cat5 specs, and this cable would work fine with gigabit.

I'm running gigabit over Commscope cat5 with no problems. I expect that the Commscope cable would indeed exceed cat5 specs. Some no-name offshore junk cat5, not so likely.

Cat 5 cable was designed for 100 megabit applications running on 2 Pairs - W/Or & W/Gn. W/Bl was set aside for Voice and W/Br for "Auxiliary functions" (Voice or...?).

Cat 5E was designed for 100 megabit applications running on all 4 pairs.

Sam

I just remembered working with cat5 cable years ago that had a different type insulation for the w/bl and w/br pairs than it did for the w/or and w/gr pairs. The insulation difference was very obvious.

Perhaps this cable is what will not work reliably with gigabit. I believe it was Berk-Tek plenum cable. Other manufacturers may have done the same thing. I vaguely remember reading there was some sort of chemical shortage which made the insulation for the w/or and w/gr pairs more expensive...so they cut corners and used a different insulation for the other two pairs.

I have not seen this type of cable, with different insulation for the two sets of pairs, since. I would venture to guess that the different insulation would alter the characteristics of the pairs enough to cause problems.


The IEEE 802.3 specs for 100baseT suggest that it was designed for use in the same cable sheath as analog telephone.