Ethernet PoE bandwidth


Need confirmation
With Cat6 cabling and PoE enabled what is the best bandwidth one can obtain ?
100 Mbps full duplex right ?

Yann ShukorOwnerAsked:
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James BunchSystems EngineerCommented:
CAT6 cabling is 1Gb/s, or 1000 Mb.
Yann ShukorOwnerAuthor Commented:
Thanks for your response James
I thought that one couldn't get full bandwidth if some of the wires were being used for PoE ?
Phillip MonkIT ManagerCommented:
From Wikipedia:

Three modes, A, B, and 4-pair are available. Mode A delivers power on the data pairs of 100BASE-TX or 10BASE-T. Mode B delivers power on the spare pairs. 4-pair delivers power on all four pairs. PoE can also be used on 1000BASE-T Ethernet, in which case there are no spare pairs and all power is delivered using the phantom technique.

...This is similar to the phantom power technique commonly used for powering condenser microphones. Power is transmitted on the data conductors by applying a common voltage to each pair. Because twisted-pair Ethernet uses differential signaling, this does not interfere with data transmission. The common-mode voltage is easily extracted using the center tap of the standard Ethernet pulse transformer. For Gigabit Ethernet and faster, all four pairs are used for data transmission, so both Alternatives A and B transport power on wire pairs also used for data.

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Yann ShukorOwnerAuthor Commented:
ok thanks Phillip, what about passive PoE then, same situation ?
Phillip MonkIT ManagerCommented:
Passive behaves like type "B", and therefore cannot accommodate Gig PoE since it expects two pair to be unused and therefore available for power injection.  It is my understanding that "Passove PoE" isn't a documented standard, so if that is what you are using I'd suggest contacting the manufacturer, as many non standard PoE implementations are commonplace.
Yann ShukorOwnerAuthor Commented:
Thanks Phillip
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