What's the minimum Cat5 length?

[MonkeyK]

I seem to recall, from a networking class, that there are minimum cable lengths based on the network type. Can anyone tell me what the minimum length is for Cat5 cable in a Fast Ethernet network? I am trying to add a switch to my router (I already know that it does not need a crossover), but can't find minimum length info anywhere.


Thanks,
Mike

 

[MichaelD]

There is no minimum length for a CAT5 cable. They come premade in as short as 1-foot lengths, used for doing exactly what you need; patching one component to another. Now, there is a MAXIMUM length of 100 meteres or about 324 feet.

 

[spidey07]

minimum length is 1 meter.

 

[eliteorange]

Originally posted by: spidey07
minimum length is 1 meter.

really?, in my networking class, there are crossover cables < 1m for trunk lines

 

[MonkeyK]

lengths depend on the type of network

 

[MichaelD]

Originally posted by: spidey07
minimum length is 1 meter.

You know more than I do; but if what you say is true, how come one-foot patch cables are sold?

 

[HypNoTic]

Your choice,

Respect the IEEE standard and use 1 meter cable CAT5 or CAT5E and avoir all line resistance issues. Same minumum apply to optic fiber but for differents reasons.

-or-

use smaller cable for your home and it will do the job but you might have an error on few millions packet you send. This kind of error is not allowed in high end telecom environnment such as Spidey talk about.


Personnally, for "home" stacking, i would use 1 foot premade cable.

 

[JackMDS]

You people do not get it.

You can go to your local Drug Store, buy over the counter "stuff" and do with it what ever you would like to.

If you are a Physician you are bound by research out come and regulation, concerning the same drugs. If you are not keeping the rules you will end with Big troubles.

Around here guys like Spidey, Scott, and others are the Network Physician. Enjoy their presence.

 

[MichaelD]

Oh...I wasn't aware that MonkeyK wanted to know the IEEE standard...I didn't know that it was 1-meter. I do now, though.

Now you've got me all nervous about the 24, 1-foot premade patch cables I already purchased.

 

[MonkeyK]

Thanks people! I had originally cut my cat5 to about 10', as I try to clean up the mess around my router, knowing 1 meter will come in handy.

No sense degrading the performance of my network needlessly.

 

[Lord Evermore]

You'd probably lose more packets due to simple radio interference or Internet congestion than you'd lose due to the short cable, as far as a home network goes.

The lengths that depend on network type do apply to things like ThinNet coax cable (10Base2). Minimum of 0.5 meters between T-connectors.

 

[cmetz]

Most modern devices try to compensate for common out-of-spec things like short cables, but some still have trouble. For example, I believe that the RTL8139 chips in many cheap NICs will have major receive errors without a software kluge.

 

[spidey07]

Yeah,

When I said the minimum length was 1 meter I was going by the IEEE and EIA/TIA standards.

For home use it doesn't matter.

 

[MichaelD]

Originally posted by: spidey07
Yeah,

When I said the minimum length was 1 meter I was going by the IEEE and EIA/TIA standards.

For home use it doesn't matter.

Why would it matter in a commercial installation, but not at home? I mean, if something is going to break at home, isn't that important too? Trying to learn...thanks.

Now I know why when I've seen pics of major commercial installations, that the patch cables are dangling all over...b/c they are too long b/c they need to be too long...always thought that looked messy...

 

[Smilin]

Originally posted by: MichaelD

Originally posted by: spidey07
Yeah,

When I said the minimum length was 1 meter I was going by the IEEE and EIA/TIA standards.

For home use it doesn't matter.

Why would it matter in a commercial installation, but not at home? I mean, if something is going to break at home, isn't that important too? Trying to learn...thanks.

Now I know why when I've seen pics of major commercial installations, that the patch cables are dangling all over...b/c they are too long b/c they need to be too long...always thought that looked messy...

Hehe no, you probably had it right the first time: It's just messy. We all put a nice neat cable rack together and spend the first few months being all anal about it and keeping it tidy but in the end they are just messy things and always end up that way. Plus it freaks out the newbies and stops them from touching anything.

 

[mcveigh]

Originally posted by: Smilin

Originally posted by: MichaelD

Originally posted by: spidey07
Yeah,

When I said the minimum length was 1 meter I was going by the IEEE and EIA/TIA standards.

For home use it doesn't matter.

Why would it matter in a commercial installation, but not at home? I mean, if something is going to break at home, isn't that important too? Trying to learn...thanks.

Now I know why when I've seen pics of major commercial installations, that the patch cables are dangling all over...b/c they are too long b/c they need to be too long...always thought that looked messy...

Hehe no, you probably had it right the first time: It's just messy. We all put a nice neat cable rack together and spend the first few months being all anal about it and keeping it tidy but in the end they are just messy things and always end up that way. Plus it freaks out the newbies and stops them from touching anything.

LMAO!! I never realized it till now but sometimes I do amke things look very dangerous or complicated to keep people from messing with it ;D

 

[dmcowen674]

Want to hear dangerous?

The reason why less than 1 meter is not recommended is because you don't get enough twists of the copper pairs to sufficiently counter act certain EMF frequencies that may degrade the signal quality.

Told you that was dangerous.

Old Engineer <---------- Now going to sleep, Niters

Edit: Below reply --- Of Course it works Fuzz, just not recommended by the head geeks and Engineers that made the spec.

 

[Fuzznuts]

well i just made up a cat with about 1cm in length excluding thr rj45's (bored ya see) and it works of course if this 1 cm of lovelyness was on a backbone trunk it may fail

 

[FabianS]

From memory, the minimum length was an issue with timing of the Ethernet signal. It only really affected 10Mb Half duplex signals, but the RFC had to allow for all options, hence for fast Ethernet, you can usually get away with much shorter. However, whe dealing with commercial or defence installations, you meet the standard so your customers can't flame you if it fails.

 

[drebo]

One foot cables exist for patching a patch panel into a switch.

Spec calls for up to 5m stranded on each end of up to 90m solid core run. Minimum length for standard is 1m.

So, if you've got a computer connected with a 3m patch cable to a 50m solid core inwall run which patches in with a 1ft patch cable to a switch, you are in spec.

 

[VirtualLarry]

From memory, the minimum length was an issue with timing of the Ethernet signal. It only really affected 10Mb Half duplex signals

That's what I had thought. Provides a minimum delay for collision-detection.

 

[Red Squirrel]

minimum length is kind of irrelevant when you are patching or otherwise plugging into a jack, because there is more cable in the wall anyway. Ex: patching a switch with a 1/2 foot cable is fine because there is more than likely more than a couple meters of wires from the patch panel to the end device.

There's also spec, and what actually works. in a super critical environment you'll follow spec because you KNOW it's been tested to those conditions, but often, you can cheat spec and be fine. For example the max run is 100m, but you could potentially get away with 150, perhaps maybe even 200. (just guessing, never actually tried it) but at that point performance is no longer guaranteed.

 

[RadiclDreamer]

minimum length is 1 meter.

This is for active connections, for switch > router for example. For patches there is no min.