We run a Netgear GS724Tv3 switch and part of the configuration per port is an option for "Lower Power Mode". The documentation for the switch lists this feature as a "Green Ethernet Configuration" feature:
A cable test is performed when this is
enabled and the port link is up at 1
Gbps: if the cable is less than 10 m,
PHYs are placed in low power mode
(nominal power)
We have purchased a set of short patch cables of lengths less than 1 m, and we might possibly be having issues with a few of them (testing is still under way). We have this feature disabled at the moment.
Should this feature be enabled if the cables between a NIC / SWITCH are less than 10 m where power consumption is not a concern? As a follow-up question, is there a minimum cable length requirement for Cat 6 gigabit?
Best Answer
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.