active / passive poe

Posted on 2013-10-09
Medium Priority
Last Modified: 2016-11-23
I was asked today if my switches were passive / active.

I searched quite a lot and only found 1 definition which was

"Active PoE has active components inside and it is able to transfer power up to 100 metres. Passive PoE uses free wires in the Ethernet cable and sends the equipments power along them to the far end. Passive PoEs range is about 30 to 40 metres / 100-130 ft that covers the needs of up to 90% of users according to our statisitics"

so I'm guessing these are not common phrases.

I have dell powerconnect 3448p with dell eps 470

going off the description above I would say we are using passive POE however can anyone else expand a bit on the differences?
Question by:CaptainGiblets
  • 2
LVL 27

Expert Comment

ID: 39559062
the 3448P does POE

i hardly believe any corporate-class switch would be passive

what do you need POE for ?

Author Comment

ID: 39559086
what is the difference between passive / active POE?
LVL 27

Accepted Solution

skullnobrains earned 1000 total points
ID: 39559227
active poe is a standard. the remote equipment and the switch negotiate the required voltage and pins to use for electric power transfer

passive works with no negociation : it makes use of cable layout described in 802.3af mode B
 (which may be selected as well in active poe) and the voltage that is setup on the switch.

note that the length is highly dependent on the required intensity. powerful devices definitively need to use high voltages if you want to go far

the wikipedia page contains more than i know, and i guess more info than you need
LVL 47

Assisted Solution

by:Craig Beck
Craig Beck earned 1000 total points
ID: 39566808
Nearly all switches will use active PoE, especially if CDP or LLDP is used.  Gigabit applications will always use active PoE if coming from an Ethernet switch.

Passive PoE, as skullnobrains said, will not negotiate any power requirements with the connecting device.  It merely supplies whatever is manually set.  This is not something you'd usually see in a network-enabled device these days, but rather in PoE splitters for example.

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