Re: POE 802.3af standard and catalyst 3560 (8 port switch)

From: WorkerBee (ciscobee@gmail.com)
Date: Sat Sep 29 2007 - 02:37:13 ART

In very layman term, there are 2 methods:

# Cisco prestandard powered device

Uses a low pass filter to allow low frequency discovery signal to loop
back to the PoE switch. This filter will detect if a PoE device is
connected.

# IEEE 802.3af device

The PoE switch uses voltage across the trx/rx pair and measure
current/voltage across the connected PoE device. A valid PoE device
will have an 25Kohm resistor across trx/rx pair to generate the
voltage the PoE switch is looking for.

http://www.cisco.com/en/US/netsol/ns340/ns394/ns147/ns412/networking_solutions_white_paper09186a008026641c.shtml

Note: If you use a power patch panel to supply voltage, it may not be
able to auto-detect if the device plug in is PoE or a non-PoE device.

On 9/29/07, Radioactive Frog <pbhatkoti@gmail.com> wrote:
> There are different implementation of 802.3af standards in different
> vendor's switches..
>
>
> I have tested that found out that cisco 3560 switch implements it using
> DATA-PAIR i.e. pin 1,2 and 3, 6.
>
> My questions are:
>
> 1. How does it actually works? supplying DC voltage and ethernet data
> through the same wires?
> 2. Do they use some sort of DSL technology stuffs (phone and data on
> different frequency?)
> 3. How does 3560 POE switch detects non-POE device? For example, plugging a
> laptop on Cisco 3560 switch and it does't blow up?
>
>
> Just curious to know.
>
>
> POE pinouts from different manufacturers STANDARDSOURCELOADREMARKS Ethernet
> RJ-45 connector pin number Source Voltage 1 2 3 4 5 6 7 8 Load Voltage DC
> Load Connector IEEE 802.3af
> using data pairs 48 V DC, protectedRX, DC+RX, DC+TX, DC-sparespareTX, DC-
> sparespare(embedded)Industry Standard for embedded PoE IEEE 802.3af
> using spare pairs48 V DC, protectedRXRXTXDC+DC+TXDC-DC-(embedded)Industry
> Standard for embedded PoE Intel, Symbol, OrinocoUsually
> 12 or 24 V DCRXRXTXDC+DC+TXDC-DC-(embedded)Most Brands of PoE Cisco
> (OLD old standard)48 V DCRXRXTXDC-DC-TXDC+DC+(embedded)Older Cisco polarity
> is
> REVERSED Cisco
> (NEW old standard)48 V DCRXRXTXDC+DC+TXDC-DC-(embedded)New Cisco is IEEE
> compliant D-Link (Adapter)48 V DCRXRXTXDC??DC??TXDC??DC??5VDC @ 2.5ADC
> coaxial
> 5.5/2.5mmD-Link PoE Adapter for non-PoE products. Apple MacIntosh AirPort
> PoE, Extreme48 V DCRXRXTXDC??DC??TXDC??DC??Converted to ???DC coaxial
> (???)Mac Polarity Unknown HyperLinkMany DC Voltages AvailableRXRXTXDC+DC+TX
> DC-DC-same as inputDC coaxial and others availableVariety of Options
> Available to Fit Most Brands of PoE NYC Wireless
> "Roll Your Own"12 or 24 or 48 V DCRXRXTXDC+DC+TXDC-DC-same as inputDC
> coaxial
> or as reqdNew York City Wireless PoE
>
> PoE - powered devices should obey following specifications:
>
>
>
>
> Frog..
>
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