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How many AP 1130 PoE can I put on 3560? Inline power Problem?

Hi friend,

i've got a big problem and i can't resolve it. I have a switch 3560 PoE with 3 AP 1130 and 10 ipphone. the problem is that the third AP can carry up he's radio interface. On the AP tells that there are no sufficient power. On the switch with the command "Sh power inline" i can see that the other AP(that working good) works with 12.3 Watt and the other (that interface radio don't work) the switch provide only 6.2 watt. So i ask you if there is a maximun power that the switch can provide. Is this possible? or what you think the problem can be? i've tried all, i change the IOS on Switch on AP i change FastEthernet on switch, i issue the command of max power on switch, but nothing change, i try to change the AP but the problem remain the same. The only thing that i see is that if i disconnect the other AP, the AP that don't carry he's interface radio up, coes up immidiatly. Have you an answer?

thanks for all

2 REPLIES
Hall of Fame Super Red

Re: How many AP 1130 PoE can I put on 3560? Inline power Problem

Hi Matteo,

This is possible, as the PoE switch only has so much available power. But in this case the numbers don't seem to add up to me. So, a few questions;

1. how many ports on the 3560- 24 or 48?

2. what make and model of IP Phones?

3. when you do the "sh power inline" what is the power budget?

4. are you running cdp?

Here are some considerations, I'm sure that we can get this working :)

Most Cisco made PDs, pre-standard or standard, support Cisco Discovery Protocol (CDP). Once power is applied to a port that contains a pre-standard or standard Cisco PD, CDP is used in order to determine the actual power requirement, and the system power budget is adjusted accordingly.

For Cisco pre-standard PDs, if CDP is enabled on the switch, 15.4W is initially allocated, and then further refined when the CDP message is received from the PD. If CDP is disabled on the switch, or if the PD does not support the Power requirements field of the CDP message, the initial allocation value of 15.4W is used throughout the duration of the connection.

For Standards based compliant PDs, the Catalyst 3750/3560 Power over Ethernet controller classifies the PD at the detection stage and allocates a required power budget based on the IEEE class. If a PD supports both IEEE 802.3af and Cisco pre-standard, the PD is detected as an IEEE device. The Catalyst 3750/3560 PoE switches classify the PD at the detection stage and allocate a required power budget based on the IEEE class. Then, a CDP message determines the actual power usage for the PD, provided that CDP is enabled on the switch. If the requested power through CDP is higher than the PoE controller classified power, the requested power is adjusted to the PoE controller IEEE class.

Most Cisco made PDs, pre-standard or standard, support Cisco Discovery Protocol (CDP). Once power is applied to a port that contains a pre-standard or standard Cisco PD, CDP is used in order to determine the actual power requirement, and the system power budget is adjusted accordingly.

This management intelligence allows better power resource allocation, because powered devices can return unused power to the PSE power budget. For example, if an IEEE 802.3af Class 3 powered device requires 9W, the PSE must budget for the full 15.4W even though the device only ever draws 9W. This wastes 6.4W on the powered device. If multiple 9W devices are present, it wastes enough power budget to deny power to other lower-power powered devices. Since Cisco Discovery Protocol explicitly signals the actual power required, the wasted power is returned to the PSE power budget.

http://www.cisco.com/en/US/products/hw/phones/ps379/products_qanda_item09186a00808996f3.shtml

PoE IEE 802.3af White Paper

http://www.cisco.com/en/US/products/hw/switches/ps5528/products_white_paper09186a008026641c.shtml

You can also try this;

If you have an earlier Cisco switch without the power negotiation code, or you use another method of power, be it a mid-span device or power injector, you need to configure the AP for injector use rather than leave it at the default power negotiation.

This is the command to specify an injector in use:

Note: This command has been wrapped to a second line due to spatial concerns.

config ap power injector enable

address in xx:xx:xx:xx:xx:xx format>where is the access point name on the controller, and is the MAC address of the switch port to which the access point is connected.

http://www.cisco.com/en/US/products/hw/wireless/ps430/products_qanda_item09186a00806a4da3.shtml

Hope this helps! Let us know,

Rob

Community Member

Re: How many AP 1130 PoE can I put on 3560? Inline power Problem

Hi Rob,

the problem seems to be with the speed negotiation. Unfortunatly we don't see that the speed of the AP were set to 10Full, and the fastEthernet of the switch were set to auto. Now we set the speed on the switch to 10 and all works good!

You think that we have resolved?

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