Ethernet cabling question

I

Ire

Contributor
Veteran XV
ok so I broke an important rule...

an IEEE rule...


for ethernet cabling what are the disadvantages to only using 2 pair?
I needed 2 jacks in a room that only had one drop.. so I split the 4 pair between 2 jacks.. and did the same for the closet....

so my question is.. what are the other 2 pair used for.. I'm thinking possible grounding but I thought I would ask..

..I had seen a 2 pair ethernet cable before that came with out cisco firewall so thats what got it in my head to do it... btw the lines are working fine I just would like to know if there is going to be a fire there for me in the morning when I go back...

lol.. tnx.. flame on
 
I always thought you only needed 2 pair.... :shrug: I do not do cabling myself tho..someone else at work does all the cabling..I hate pulling cable.
 
Using two pair only you can only have one device sending at a time, with a full four pair set up it would be possible for the devices to be sending and recieving at the same time increasing the speed. If it's just for workstations you probably won't notice a huge difference.
 
Temujin said:
Using two pair only you can only have one device sending at a time, with a full four pair set up it would be possible for the devices to be sending and recieving at the same time increasing the speed. If it's just for workstations you probably won't notice a huge difference.
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obviously you dont understand or you are a moron... but thx for playing

any1 know fo'sho?
 
Nevermind you dimwits.. I found it...

for the record you only use 2 pair for ethernet 10/100baseT 1,2,3,6
the only standard that uses all 8 is GBbaseT

*bows*
 
yeah but i thought you were asking about crosstalk, which is why it's taking so long for me to research and reply. i found a site that spoke about the function of twisted pairs preventing crosstalk, but i don't believe there is any mention about not using the other 2 pairs for an additional 10/100 drop.

i could've told you about that gigabit thing. :p
 
2 pair last I checked was for 10mb only. Correct me if I'm wrong but if you want 100mb you need 4 pair. Gb speeds are 4pair and much tighter specs on the wire.

edit: sounds like you got your answer. blarg :hrm:
 
I did find one gay site that listed the other 2 pair all as grounds.. but thats the first I've seen of it...

although now that I think of it.. why would you string the grounds of 2 different machines across a long fucking antenna.. hmmm
 
You sure about 10\100 being 2pair? My last gig we ended up using some splitters and had to hard set some of the nics to 10mb otherwise they wouldn't work.
 
SaintDude said:
You sure about 10\100 being 2pair? My last gig we ended up using some splitters and had to hard set some of the nics to 10mb otherwise they wouldn't work.
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yes, but you get more crosstalk, on longer runs this will force you to down the connection to 10mb

it works, but its quite a nigger-rig
 
Yeah SD I'm positive it's 2 pair.

Ire, it's not so much that you're stringing ground through. You could leave those disconnected for all it cares. It's the fact that material exists between the other 2 pairs that matters. Or at least that's what I thought it was. I was always told that the reason the 586A/B standards existed was to make sure that the Rx and Tx lines weren't right next to each other throughout the length of the cabling.

Evidently I'm wrong because there's no mention of that. Only that the pair you choose for each of Rx and Tx are to be the same color (twist) for that pair.

I think you're fine.
 
....cross talk only happends when you untwist everything like a moron..

I r teh not


thx invar.. like I said.. I have seen cisco ethernet cables that are only 2 pair.. I'm just wondering why everyone uses all 8... if not for the electric guys charging per drop.. *shrug*?
 
if it works, it works... you may get a little reduction in performance, but no biggie.
incidentally, doing this works better w/ higher quality cable (more twists per inch)
 
expansion ..to.. GBbaseT?

..my friend was tryin to convince me its so if you are in a crunch you can swap pairs.. but I still think the wiring closet would be oh-so-clean if you only used 1 drop for.. um.. 2 drops.. hehe.. but what do I know my cisco book is only good for the fire..
 
Ire said:
expansion ..to.. GBbaseT?

..my friend was tryin to convince me its so if you are in a crunch you can swap pairs.. but I still think the wiring closet would be oh-so-clean if you only used 1 drop for.. um.. 2 drops.. hehe.. but what do I know my cisco book is only good for the fire..
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yep, Gigabit uses all 8

and halving the number of drops would likely have an effect on network performance; adding crosstalk / interference to the whole network :p
 
You can use whatever you want to use, just don't expect it to live up to the bandwidth or distance specs of the Cat5 standards. I've seen a single pair run over a 10Mbit repeater setup before, but I wouldn't recommend it.
 
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