Cisco switch “inline power denied”

I had a curios problem with the new Cisco Aironet access points “AIR-AP2702I-UXK9”. This are universal (country-independent) APs. After several seconds, the access points from this series (connected directly to the PoE switches) made a power reset. Powering this APs with PoE-Injector solved the problem. The Cisco switches used in the environment are 3550 series. The installed firmware is from 2004 and I thought it could be a problem with CDP and PoE. So I debugged CDP events on the Cisco switch. The AP starts again (without the injector) and after the reset, I could see the following debug messages:

012844: Aug 22 09:51:45: CDP-EV: Unrecognized type (22) seen in TLV
012845: Aug 22 09:51:45: CDP-EV: Number of addresses <0> in Address Tlv is NOT > 0
012846: Aug 22 09:51:45: CDP-EV: Number of addresses <0> in Mgmt Address Tlv is NOT > 0
012847: Aug 22 09:51:52: CDP-EV: Unrecognized type (22) seen in TLV
012848: Aug 22 09:51:52: CDP-EV: Invalid protocol type (0)
012849: Aug 22 09:51:53: CDP-EV: Unrecognized type (22) seen in TLV
012850: Aug 22 09:51:53: CDP-EV: Invalid protocol type (0)
012851: Aug 22 09:52:49: CDP-EV: Unrecognized type (19) seen in TLV
012852: Aug 22 09:52:49: CDP-EV: Unrecognized type (22) seen in TLV
012853: Aug 22 09:52:49: CDP-EV: Invalid protocol type (0)
012854: Aug 22 09:52:49: %ILPOWER-5-ILPOWER_POWER_DENY: Interface Fa0/11: inline power denied

Normally, the APs are taking 15 or 15.4 watt power but the 2700er series needs at least 16.8 watt to run at “PoE/Full Power”. So it asks via CDP to get more. The old switch (or maybe the old firmware) doesn’t understand the new AP CDP, so the switch denys inline power as a precaution. Deactivating CDP on this specific port also solves the problem, but the AP is running in “PoE/Medium Power” (which is not good; Cyclic Shift Diversity (CSD) disabled, 2 of 4 transmitters disabled, data rates MCS  8-15 disabled), no spatial stream possible, etc.; see here and here).

Maybe a firmware update could solve the problem, we couldn’t test this by now. The customer will use newer switches at the new aimed location.

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