SRW2024P Phantom Power

Answered Question
Oct 20th, 2009
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Do you know if this switch is capable on providing PoE over data lines (i.e. phantom power), so that a 1000Base-T device can be powered up with PoE?

I cannot find any such information on the manual or the net.


I am going to buy a Routerboard 600 (http://www.routerboard.com/pricelist.php?showProduct=55) that supports 1000Base-T and PoE at the same time, and I would like to check if the switch supports it too.


Thanks.

Correct Answer by chrcoope about 7 years 6 months ago

This test was conducted from a windows seven workstation plugged into an slm2005 switch plugged into an sge2010p plugged into a sge2000 to an xp workstation using "eththrough". screen shots are in the attached document.


Chris

Correct Answer by chrcoope about 7 years 6 months ago

I have had a chance to lab this. The results are positive. I will post screen shots sometime today.

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Glenn Quesenberry Tue, 10/20/2009 - 07:23
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The SRW2024P provides 24-10/100/1000 ports as well as 802.3af compliant Power over Ethernet (PoE).  It will provide 7.5W of PoE per port on all 24 or the 802.3af maximum of 15.4W on 12 ports simultaneously.  If this is what you mean by "phantom power" then you should have what you need.  I've personally only encountered that term with audio devices like say a microphone that needs "phantom" power, but I guess the concept is the same.  This information is contained in the Data Sheet here.


Hope this helps!


Glenn

CostaTsaousis Sat, 10/24/2009 - 02:01
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Thanks for the answer.


Check this in wikipedia (http://en.wikipedia.org/wiki/802.3af):


Power over Ethernet is usually implemented following the specifications in IEEE std. 802.3af-2003 which added clause 33 to the IEEE 802.3 standard. It allows the powering device to use a voltage between 44–57 V DC, though the nominal voltage is 48 V, over two of the four available pairs on a Cat. 3/Cat. 5e cable with a selectable current of 10–350 mA subject to a maximum load power of 15.40 W. Only about 12.95 W are available after counting cable losses, and most switched power supplies will lose another 10–25% of the available power. A "phantom power" technique is used to allow the powered pairs to also carry data. This permits its use not only with 10BASE-T and 100BASE-TX, which use only two of the four pairs in the cable, but also with 1000BASE-T (gigabit Ethernet), which uses all four pairs for data transmission.


In other words, I want to provide power to a device while having a gigabit speed with it. This is also called "power over datalines". Do you know if SRW2024P support it? The datasheet does not nention it, and I don't know if this is a 802.3.af feature.


Thanks.

chrcoope Mon, 10/26/2009 - 07:26
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Costa,


802.3af is the standard that will allow you to push PoE over full duplex gigabit Ethernet. Excellent question and good research on you part.


The SRW2024P does not appear to fully support 802.3af according to the data sheet unlike the SGE2010P for instance. 802.3af is either listed under standards, or it is not.


Thank you,

Christopher

CostaTsaousis Mon, 10/26/2009 - 13:08
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Thanks.


So, you are suggesting that, most proabably, SRW2024P will fail to provide PoE and gigabit speed on the same port.

Is that right?


This is important for me, since I am going to buy the specific routerboard just because it can be powered by PoE and have a gigabit speed at the same time.

If it is not going to work on the switch, I'll buy something completely different.


Thanks again.

chrcoope Tue, 10/27/2009 - 06:06
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That is what the data sheet seems to indicate. I would like to test this in my lab but time is precious. I would like to think I can test this sometime today though. I will let you know how I test, and what I find.


Regards,

Christopher

chrcoope Wed, 10/28/2009 - 06:07
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Unfortunately I was unable to fully test this yesterday. I was going to take an SRW2024P and uplink an SLM2008 as it uses PoE from the SRW to power itself and then do an ftp across the uplink with two gigabit computers. This morning I was informed that I would not be able to continue this until next week. If you call in to the SBSC at 866.606.1866 and start a case and remain on the phone with an engineer while this test is performed, we can get it done then.


Regards,

Christopher

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chrcoope Fri, 11/06/2009 - 07:26
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I have had a chance to lab this. The results are positive. I will post screen shots sometime today.

Correct Answer
chrcoope Fri, 11/06/2009 - 07:54
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This test was conducted from a windows seven workstation plugged into an slm2005 switch plugged into an sge2010p plugged into a sge2000 to an xp workstation using "eththrough". screen shots are in the attached document.


Chris

CostaTsaousis Mon, 11/09/2009 - 03:56
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Thank you very much.


I can confirm that. I brought the RB600 mentioned at the beginning and yes, it is powered from SRW2024P via PoE and its network speed is 1Gbps.


Thank you very much.


Costa

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