Problems with POE when migrating Cisco Switch IOS

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Feb 4th, 2010
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HI all:


We have several switches PoE Cisco 3560 (cisco WS-C3560-48PS (PowerPC405) processor (revision Q0)  for our IP phones. We needed to migrate to a SSH enabled IOS (c3560-ipbase-mz.122-35.SE5)
The IOS we got was: c3560-advipservicesk9-mz.122-46.SE.bin


Then, we updated and we got problems with some switches as they were delivering 15,4 to all ports PoE ports, therefore, consuming all 370 W in less ports than available. That provoked that some phones were out of energy.


As a workaround, we set power inline to 7 watts in all ports, but there should be another solution, right?


Thanks in advance


W.

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sachinraja Thu, 02/04/2010 - 13:08
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Hello Walter


Do you want to check your CDP settings after IOS upgrades ? your switch uses CDP to do intelligent power management.. did you try power inline auto ? You can look at this document to know more on the POE settings on edge ports:


http://www.cisco.com/en/US/docs/switches/lan/catalyst4500/12.2/25ew/configuration/guide/PoE.html


if you are having issues of the switch supplying power to some POE ports, you might have to look at this bug related to the IOS specified:


CSCsu58581 - Switch stops providing power on PoE ports


It may give the following error message in this case:


%FRNTEND_CTRLR-1-SUB_I2C_ERR: Sub 0 reported 36B5B98 I2C errors
%FRNTEND_CTRLR-2-SUB_INACTIVE: The front end controller 0 is inactive


If the switchport is giving power, but allocation 15.4 mW to all phones, it is a good practice to manually enable power for ip phones using the power-inline command


Hope this helps.. all the best


Raj

glen.grant Thu, 02/04/2010 - 14:28
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Your fix is the correct one for non cisco phones.  You have to figure out the power budget by how much the device draws at max and how much the particular switch is capable of providing .  We just ran thru this with Nortel phones.  I believe only cisco phones will automatically throttle themselves back and it does this thru a mechanism using cdp . Don't know of any other workarounds .  This is all part of the network planning process when using non cisco phones.

walter.perera Fri, 02/05/2010 - 03:03
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Hi Glen:


Thanks for your answer. In fact we are using Cisco 7940, 7931 and 7906 as phones?.


Regards

walter.perera Fri, 02/05/2010 - 03:06
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Hi Raj:


Thanks for your reply. In fact, due to security hardening, we disabled cdp with previous IOS version, without issues (I suppose because phones were already there, and we did not shut down switches), but maybe when changing IOS and restarting, some switches took CDP disabled and then started distributing all 15,4 in all possible ports.


What do you think?


Thanks


W.


BTW: CDP is enabled by default in POE switches?

walter.perera Mon, 02/08/2010 - 03:24
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Problem was that CDP had been disabled. We reenabled it and set power inline as auto, and it solved issue.


Thanks to all


W.

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