Cisco switch PoE problems

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Feb 19th, 2009
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please can someone tell me when does a switch Catalyst 3560 power on the port configured with PoE inline power auto ?

I've a customer with PoE Thomson phones and the switch bring on the Giga ports after 15/30 minutes.

I've checked the power used by the phones with the command "sh power inline" and there's enought power.

#sh power inline

Available:370.0(w) Used:74.2(w) Remaining:295.8(w)


Roberto Taccon

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Eric Hansen Thu, 02/19/2009 - 06:22
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We use 3560's with Avaya phones and dont have any problems. Do you know what the distance of your cable is between the phone and the switch? Ive had problems getting power to anything that is over 100feet away. Have you certified your cable plant? When the phones finally get power do they actually work?

ericn8484_2 Thu, 02/19/2009 - 06:23
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We have around 80 3560 switches in our environment using mostly 7940 Cisco IP phones. The PoE starts immediately when we plug in our phones. I have never seen a delay to get power to the phones unless the PoE is disabled on the switch. However since you say it starts after 15 to 30 mins, its not because the switch has PoE disabled.

Do you have more than one 3560 switch to test on to ensure its not something faultly with your switch. It would seem to me that it is more likely a problem with your phones.

srinivas_816 Thu, 02/19/2009 - 06:34
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1) Switches that support Cisco Enhanced PoE use Cisco Discovery Protocol to auto-negotiate a power level in excess of 15.4W per port.

2) The Cisco Enhanced PoE switch informs the powered device (PD) of the power level it is capable of providing, and the powered device then selects the appropriate power level.

3)The connector automatically senses when the internal power supply of a connected device fails and provides power to the failed device, preventing loss of network traffic

Leo Laohoo Thu, 02/19/2009 - 14:11
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Depends on the model of the switch. Do you have the STANDARD 48-port PoE switch? If yes, then the 48-port switch (2960/2975/3560-3750) can only power 24 out of 48 ports.

Does this help?


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