What is the minimum Ethernet cable length for a Cat 6 gigabit connection?
Solution 1:
This question is still missing an authoritative reference, so here it goes:
There is no minimum length specification to a 1000BASE-T segment.
Charles E. Spurgeon - Ethernet, the Definitive Guide, p. 163.
Solution 2:
According to http://www.ctrlink.com/2006_07_01_archive.html there is no minimum length when using a star topology (one node connected to each port of a switch). In the older times, when you had an Ethernet ring, there had to be minimum distances between devices to prevent impedance problems on the ring.
Concerning the low power mode, are you sure that isn't related to POE? I don't see how you can lower the power and still meet the guideline for voltage. Based on the impedance of the cable, the power consumed will be directly related to the voltage put on the cable by the NIC... See Ohms law, which isn't perfect when you are talking high-frequency waveforms, but the same principles still apply.
Solution 3:
I've never seen a minimum cable length recommendation. This feature seems like a fairly straightforward power-saving feature. Shorter cable runs incur lower power loss.
According to the NetGear documentation, there are actually two separate power modes, both of which can be enabled. One of the modes is for cable less than 10 meters.
http://kb.netgear.com/app/answers/detail/a_id/11701
"What are the Green Ethernet Features?
"GS716Tv2 and GS724Tv3 support two power saving modes: Auto Power Down Mode and Short Cable Mode. Both features can be enabled at the same time. When Auto Power Down mode is enabled, power will saved for ports that have no link. When Short Cable Mode is enabled, the device will check the cable length and reduce the output power if the cable length is less than 10 meter."
Here is a fairly good overview of the TIA-568-B recommendations and practices:
Solution 4:
I can't find a link to the spec (which isn't suprising as TIA sells it) however seimon has a pretty good selection of summaries. There is no mention of a minumum length but there is one since the minimum bend radius dictates it for the cable (4 times the cable diameter for horizontal UTP cables under no load conditions- I'll let some math wizard figure that arc length out). It's certainly less than 1M. Here is the summary of cable practices here: TWISTED-PAIR CABLING INSTALLATION PRACTICES
There is a guideline in ANSI/TIA/EIA-568-B.1 that says the consolidation point should be located at least 15 meters away from the telecommunications room to reduce the effect of connectors in close proximity.
Also note that (particularly older cat6 cable) some cat6 cable has splines that will prevent the cable from exceeding the minimum bend radius and will most certainly not be useful shorter than about 2 ft. I haven't seen much of that out there but it's out there.
Solution 5:
To the best of my knowledge there is no minimum cable length beyond the practical (how closely can you get the connectors to each other and successfully terminated).
I have personally used Cat5e cables in the 4 and 6 inch range at Gig speeds without any issues. (This was with Cisco 3500/3550/2960 switches it should be noted).
This is pure speculation but, the "Lower Power Mode" sounds like the switch will energize the conductors/pins with less electric power at shorter distances. I don't know how much power savings this could possibly be -- perhaps their literature has projections?