What is Minimum Length between Nodes/patch cables.

[Nuwave]

Hi,

I've been searching a bit on the internet and get some conflicting information that I hope someone can clear up for me.

Is there a minimum length for Cat 5, Cat 5e, Cat 6 patch cables?

Is there a minimum length of cable required between nodes (IE a router plugging into a switch).

Reasons if there is a minimum would also be appreciated.

Thanks!

 

[gsaldivar]

There are maximum length limits, but no minimums as far as I know.

 

[Qrilock]

As long as the link is full duplex there is no minimum cable length requirement. As I understand it there are some issues with CSMA/CD with extremely short cable lengths, but this would only be relevant in an environment where collisions are going to occur. If you have collisions between your router and your switch something is horribly wrong...

I have a routing/switching practice lab set up, I have cables as short as 4 inches. Everything works fine.

 

[imagoon]

Hi,

I've been searching a bit on the internet and get some conflicting information that I hope someone can clear up for me.

Is there a minimum length for Cat 5, Cat 5e, Cat 6 patch cables?

Is there a minimum length of cable required between nodes (IE a router plugging into a switch).

Reasons if there is a minimum would also be appreciated.

Thanks!

I think it is 1 meter total length [from memory]. So a 4 inch patch still works since there is wall cable etc. 4inch cable from a switch to a NIC card may fail since the signal is "too hot"

 

[drebo]

Yeah, minimum recommended is ~3ft. It probably works when shorter, but is out of spec, so I wouldn't recommend it.

 

[spidey07]

Minimum is 1 meter, don't break it. This is between active ports (like a NIC and switchport).

 

[VirtualLarry]

I've got some 1' CAT6 cables, connecting my 10/100 router and gigabit switch. Seems to work for me.

 

[spidey07]

I've got some 1' CAT6 cables, connecting my 10/100 router and gigabit switch. Seems to work for me.

The point is, yeah, it works, but you're outta spec so results aren't guaranteed.

I've seen it cause problems. Don't fuck with the physical layer.

Understand that I'm called in to diagnose "weird shit", my first analysis is cabling. Don't fuck with the physical layer. Huge data centers with "weird shit", first stop is cabling...ALWAYS. Don't fuck with the physical layer.

 

[ScottMac]

The point is, yeah, it works, but you're outta spec so results aren't guaranteed.

I've seen it cause problems. Don't fuck with the physical layer.

Understand that I'm called in to diagnose "weird shit", my first analysis is cabling. Don't fuck with the physical layer. Huge data centers with "weird shit", first stop is cabling...ALWAYS. Don't fuck with the physical layer.

Couldn't have said it better myself.

When you build a network, cabling / the physical layer is the foundation; with a flaky foundation, the chances of having a flaky network is significantly higher.

If there's any issues that ultimately end up being resolved legally, be prepared to explain to the nice judge and jury why you decided to not follow the specified infrastructure guidelines (that are usually based in some physical principle (like feedback loops) or scientific wrinkle ... whether you agree with it or not).

 

[imagoon]

Couldn't have said it better myself.

When you build a network, cabling / the physical layer is the foundation; with a flaky foundation, the chances of having a flaky network is significantly higher.

If there's any issues that ultimately end up being resolved legally, be prepared to explain to the nice judge and jury why you decided to not follow the specified infrastructure guidelines (that are usually based in some physical principle (like feedback loops) or scientific wrinkle ... whether you agree with it or not).

Agreed. People wonder why I am so anal about this also.

 

[Nuwave]

Thanks everyone for your replies. Is there an RFC or IEEE spec that specifically states this?

I have always thought 1 meter was the minimum but I can't actually find an official spec that states this.

 

[spidey07]

Thanks everyone for your replies. Is there an RFC or IEEE spec that specifically states this?

I have always thought 1 meter was the minimum but I can't actually find an official spec that states this.

Should be in EIA/TIA 568

 

[unokitty]

I've always heard that the minimum UTP patch cable length was 1 meter. (If my memory serves me correctly this was due to the possibility of signal reflection?) Though, I haven't actually read the spec.

The Telecommunications Industry Association (EIA/TIA) makes the 568c standard. I would suspect that the minimum length is listed in there.

And for a mere $989, they will sell you a copy.

Note that being out of spec does not necessarily mean that something won't work... It just means that it is "out of spec."

If you are building your home network, it may, or may not, matter to you. If you are building a commercial network that has a contract specification of meeting the 568c standard, then likely it does matter.

Best of luck,
Uno