patch cable length?

[lleo19]

Hi All,
This may be trivial information, but I am having hard time settling the issue on what is the minimal length needed for Cat5e patch cables?

For example: if I want to connect two cascading switches mounted next to each other - how long the patch cable has to be?
I also have a number of devices (NAS, AP, servers, router, etc) in a rack that connect to a switch and is there a minimum length that one has to respect for optimal use?
Thanks, Lleo19

 

[thiggins]

There is no minimum length that I know of.

 

[lleo19]

Great, thanks!
Searching the web for this information yielded conflicting information.
What seems clear is that the IEEE standard specifies a minimum length of 2.5ft between nodes. Now does two switches qualify as two nodes? I think yes, but then again there are many who report no issues with cables only few inches long.
Cheers, Lleo19

 

[Jay_S]

Now does two switches qualify as two nodes? I think yes, but then again there are many who report no issues with cables only few inches long.
Cheers, Lleo19

I'm pretty sure that any sort of "repeater" (a switch = a "multiport repeater") is considered a node. I have a lot of 1-ft cat6 cables in my home (from patch panel to switch, and from PC's to wall plates), but not between 2 nodes. You could always buy some short patch cables and test them. 1-foot cat6 patch cables are $0.75 each:
http://www.monoprice.com/products/subdepartment.asp?c_id=105&cp_id=10232

 

[YeOldeStonecat]

Great, thanks!
Searching the web for this information yielded conflicting information.
What seems clear is that the IEEE standard specifies a minimum length of 2.5ft between nodes. Now does two switches qualify as two nodes? I think yes, but then again there are many who report no issues with cables only few inches long.
Cheers, Lleo19

Where did you find that?

The only specs I've seen..there is no minimum length for cables. You can go to just about any cable manufacturer and get 1' patch cables. Look at many business/enterprise networks..you'll see 1' cables uplinking switches and patch panels...heck even 6" cables.

However....many testing devices will be inaccurate when it comes to attempting to measure short patch cables...such as under 1 foot in length. Thus the rumor started to spread that there is a minimal length.

 

[Jay_S]

Where did you find that?

Here's one reference:
http://www.protocolbase.net/protocols/protocol_Ethernet Type 2.php
Ctrl-F and search "minimum length between nodes" - it says 2.5M for 10Mb/s and 100Mb/s, but not for gigabit. It might not apply for gigabit.

You can go to just about any cable manufacturer and get 1' patch cables. Look at many business/enterprise networks..you'll see 1' cables uplinking switches and patch panels...heck even 6" cables.

Well, since patch panels are just passive devices (if you can even call them "devices"), the additional 6" patch cable length just gets added to the length of structured cabling that terminates at the patch panel. So you're not breaking the 2.5M rule/rumor.

Having said all this, I don't think it's an issue with any copper star topology. I think the min cable length requirement was necessary due to impedance mis-match & subsequent reflections when using a bus topology.

There are lots of differing opinions...
http://forums.overclockers.com.au/showthread.php?t=698623

 

[YeOldeStonecat]

Well, since patch panels are just passive devices (if you can even call them "devices"), the additional 6" patch cable length just gets added to the length of structured cabling that terminates at the patch panel. So you're not breaking the 2.5M rule/rumor.

Guess I should have left out patch panels...but everything else next to them on the COM rack/cabinet, you'll have switches uplinked to each other, a router uplinked to the main switch, etc. Same...under 1 footers.

Still can't find an authoritative reference site.

 

[Jay_S]

Still can't find an authoritative reference site.

Yeah, neither can I. I've tried a few seaches using:

ethernet minimum length +site:cisco.com
ethernet minimum length +site:intel.com

Yields nothing of interest regarding copper.

 

[rickeo]

These little baby's work fine for me. Pretty short.

http://www.hdimage.org/images/580p90g0m0y7knlh4xog_9989.jpg

 

[YeOldeStonecat]

These little baby's work fine for me. Pretty short.

http://www.hdimage.org/images/580p90g0m0y7knlh4xog_9989.jpg

That's what I strive for on my cabinets 'n racks.

 

[NetQ]

I use a lot of short lengths and there is no issue. You need to pick the lengths that gives you the room to dress the cabinet in the best way. I would recommend using patch cables that are UL Rated and made from true 350Ghz Cat 5e cable or if they are Cat 6 they should be made from 550 Ghz cable. I know a lot of stores like monoprice use cheap cat 5e cables that are low in copper content and may be made from cables that are not UL Rated or are lower speed cables. So I would look at what the patch cable is made of. If it isn't documented then you are taking a risk. I use a lot of ICC, Unicom, Panduit, and Siemens patch cables. There is no question of quality and speed. I would pay the extra dollar to ensure quality. Here is a source I recommend.

http://www.cablegiant.com/default.aspx?p_id=1&c_id=69