Power inline issues with 3850 switches

[Jeffrey Garcia]

Would like to know how 3850  Version 03.02.02.SE computes and allocates poe requirements.

As seen below we have stacked 4 3850 and switch 3 only has about 160+ watts. Is there a fix to this problem. 

We have connected avaya phones to all switches but no errors found except on stack 3.

Module       Available     Used Remaining
(Watts)       (Watts)         (Watts)
------ --------- -------- ---------
1 616.0         585.0             31.0
2 719.0         688.8             30.2
3 162.0         161.0             1.0
4 568.0          221.2            346.8
5 390.0          8.0                382.0

Jan  7 04:23:43.277: %ILPOWER-5-ILPOWER_POWER_DENY: Interface Gi3/0/48: inline power denied. Reason: insufficient power

[Philip D'Ath]

The switch tries to negotiate with the attached device its PoE requirement.  If that works, that is what it gets.  If the device does not support the negotiation the switch has to allow the full power allowance that the port can handle to be safe.

Have you got the power stacking cables plugged in (not the data stacking but the power stacking)?  If you have, then the stack of switches can share the power from all power supplies amongst all switches, and it should even up nicely.

Either that or you can buy a bigger power supply (or a second one if it only has one) for the third switch - but using the power stacking connectors would give you a good solution.

[Jeffrey Garcia]

Ok, thanks for the info. Greatly appreciate it.

[Philip D'Ath]

This has info on physically connecting up StackPower.

http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3850/hardware/installation/guide/b_c3850_hig/b_c3850_hig_chapter_010.html#concept_971E5E644A094ABEB52C4911E6BA154B

[Jeffrey Garcia]

I will try to contact on-site engineer to check the power stacking cables since this switch is located at a remote site. Thanks.

[Philip D'Ath]

You can try a " show stack-power" to verify that the stacking cables are plugged in correctly.

http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3850/software/release/3se/int_hw_components/configuration_guide/b_int_3se_3850_cg/b_int_3se_3850_cg_chapter_01000.html