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AP-535 and single 802.3bt POE

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  • 1.  AP-535 and single 802.3bt POE

    Posted May 25, 2022 10:41 AM
    We currently have some AP-535s connected to a Cisco Mgig capable switch on a single power supply, but the AP is still only requesting 802.at POE+ instead of 802.3bt POE++ despite the switch being capable of allocating 60w per switchport. 

    Interface Admin  Oper       Power   Device              Class Max


    --------- ------ ---------- ------- ------------------- ----- ----

    Fi1/0/36  auto   on         27.5    Ieee PD             4     60.0 

    The switch has more than enough power budget: 

    Module   Available     Used     Remaining

              (Watts)     (Watts)    (Watts) 

    ------   ---------   --------   ---------

    1          1745.0      272.0      1473.0

    It may be difficult for us to get an additional power supply to the APs for various complicated reasons, so we were hoping to be able to power the APs with a single 802.3bt power supply - as stated on the 530 data sheet, in order to run without restriction. Currently these APs will be operating in restricted mode, due to inefficient power supply. 

    We have other AP-535s across our estate which have 2x 802.3at power supplies which then run at 802.3bt. It is definitely possible to run on a single 802.3bt?

    Where does the problem lie?

    Adam Newson

  • 2.  RE: AP-535 and single 802.3bt POE

    Posted May 25, 2022 08:38 PM

    Is the POE source 802.3bt compliant or is this Cisco's UPOE proprietary variant?
    The AP-535 definitely can be powered from a single 802.3bt source and operate without restrictions, but it may not identify the switch as such.
    Can you check the output from the following CLI command?
        show ap debug system-status ap-name <name> | begin "Power Status"
    Note that even when it's on class 4 POE. the AP-535 only applies two restrictions: the USB port is disabled, as well as the second/other Ethernet port.
    If those features are critical, you could consider enabling the IPM feature, which will only apply restrictions when really needed (based on real power consumption), and allows you to define the order/priority of restrictions that may get applied.
    Since there's a big difference between typical and worst-case power consumption, of APs and most APs are operated and configured in a way that worst case power consumption is never reached, the IPM feature can help to take advantage of that.
    In 99% of AP-535 deployments, this AP will not need more than class 4.

    Onno Harms

  • 3.  RE: AP-535 and single 802.3bt POE

    Posted May 27, 2022 07:00 AM
    Thanks for comments. 

    As it turns out there is an additional command to run on the Cisco 9300 switch which enables 802.3bt negotiation. This is not enabled by default, the switch will negotiate at 802.3at automatically. This has been tested and now the AP-535 is running at 802.3bt on a single power supply. The command does reload the entire switch, though. The AP-535 was then able to negotiate at 35.2w on a single and 2x 22.1w on an LACP dual link.

    Adam Newson

  • 4.  RE: AP-535 and single 802.3bt POE

    Posted May 26, 2022 02:31 AM
    Look at Cisco switch LLDP Poe settings, and the TLV
    start here:
    show interface-profile lldp-profile PoE
    show lldp neighbor interface gigabitethernet X/X/X detail
    show neighbor-devices interface gigabitethernet x/x/x detail

    and, subsequently at your own discretion:

    (config) # interface-profile lldp-profile PoE

    (LLDP Profile "PoE") #lldp transmit

    (LLDP Profile "PoE") #lldp receive

    (LLDP Profile "PoE") #lldp tlv-select power-management

    (LLDP Profile "PoE") #lldp med-tlv-select power-management

    (config) #interface gigabitethernet x/x/x

    (gigabitethernet "x/x/x") #lldp-profile PoE

    or try a external power..

    Steinar Grande