Cat 5e vs 6 and gigabit ethernet

Last year, I bought, maybe, my last box of Min Compliant cat-5e cable. A customer called and wanted to know why he can't send his new GIG ethernet stuff over the cable.

So I got to thinking. Has anyone tried pushing GIG over 5e? The customer says that his manual says it can be done. Gee I wish I'd used better cable and jacks.

It looks like the price is going to be double for jacks and wire, 50% more for patch panels, and Patch cables will retail for $10-20 each. The switch is about 25% more, but he said the network cards were really expensive, but he bought a Dell through Dell.

Anyone have any more input?

Carl Navarro

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Carl Navarro
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About a year ago I wired an office with Cat5E. 30 computers (mostly doing gig), 3 HP 28xx switches, Leviton 5e Jacks.

Are you sure it's not his cheap (or just unable to sync up) switches, nics, patch cables, etc... that are keeping him down? Are his switches managed? If so you might try some long patch cables between one of them and a few computers and see what happens that way vs the existing network.

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Gigabit ethernet (1000base-T) is designed to work over CAT5e cable.

So assuming the cable and everything (jacks, patch panel, patch cords, etc.) is CAT5e compliant, it will work.

On difference is gigabit ethernet uses all 4 pairs instead of 2. So if you have a miswiring problem this creates a scenario where it may work on

100base-TX and not 1000base-T.

Anyway, you don't really say what kind of problems your customer has (he might just have some kind of configuration error). Gigabit ethernet, while in theory is 10x faster, will not give you 10x faster throughput in general usage.

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Well, it's rather hard to base an expensive decision to re-do your customer's cabling on an "it does not work" claim. First of all, if they are trying to measure a throughput, it is never going to be 1000 MBit/s due to lots of redundant info sent along with the actual data. Also, most people (that don't do this for living) measure throughput in MByte/s and forgot to multiply the figure by 8 to get the number of Mbit/s. And, even more importantly, there is only handful of PCs out on the market that can actually generate a 1000Mbit/s stream of data. There are all kinds of hardware limitations INSIDE the PCs, sending and receiving, not even mentioning the Ethernet switches in between.

In any case, if it was minimally *COMPLIANT* CAT5E, you tested it fine and the customer did not use trashy 5-years old patch cords, they should look elsewhere for the real source of the problem.


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Carl Navarro wrote in part:

I've never heard of this stuff. The mfr either claims the cable can be used to make a Cat5e link, or it cannot. It _is_ true that some cable has more headroom than others, and big reels will have test results attached. But I wouldn't expect headroom to matter except on longer, near max links.

This is a customer relations nightmare, and also shows the strongest reason to run cert tests. Once you have cert tests in hand, it becomes the actives' problem. Which it most likely is.

Sure. All day long.

If you have serious doubts about the jacks, rejack. It is much cheaper than repulling, and is most likely the problem, especially on shorter runs.

Sure. As others have said, actually getting 1000 Mbit/s through the actives is hard to do. Very few PCs can keep up, and they're all server-class machines. Regular PCI cards max out around 300 Mbit/s.

-- Robert

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Robert Redelmeier

Ya, Carl as long as you certify the cable your off the hook....

Did you???

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Cat 5e is supposed to do gigabit, and anything less than about 80m I would expect regular Cat5 to do it, also. Note that gigabit is much more sensitive to how much wire is untwisted than 100baseTX, and also that it uses four pairs instead of just two. Still, if it certifies as Cat 5e, it should do it, and most likely also for Cat 5.

Most likely there is some other reason for it not to work.

-- glen

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glen herrmannsfeldt Forums website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.