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  • 1.  Power specifications 5400R-zl2 modules

    Posted Jan 19, 2022 09:11 AM
    Hello all,

    In a temporary building I need to power 230 access points which use 15W (or 30W PoE when the access point itself powers another device). We use our standard Aruba 5406R-zl2 switches to provide the location with network connectivity. We only use the following two module types in our switches:
    • Aruba 20-port 10/100/1000BASE-T PoE+/4-port 1G/10GbE SFP+ MACsec v3 zl2 Module (J9990A)
    • Aruba 24-port 10/100/1000BASE-T PoE+ MACsec v3 zl2 Module (J9986A)
    While I know there is a maximum power budget available depending on the power supply used, my question is: What is the maximum power capacity per module? I cannot find anything in documentation (HP Switch v3 zl2 Modules Installation Guide). Everything I find says "each port can deliver 30W power for PoE", but if I calculate 24 ports x 30W then I get 720 Watt / module (which sounds like a lot of power for one module to handle).

    When I look on random production switches I get various "Maximum Power" results. Sometimes I see numbers as low as 388 Watt, sometimes 633 Watt. In the example below the same module is seated in slot A and slot F, but slot F has a couple of access points connected while slot A has not.

    switchA# show power-over-ethernet slot a

 Status and Counters - System Power Status for slot A

  Maximum Power       : 523 W           Operational Status  : On
  PSE Power Reserved  :   0 W           Usage Threshold (%) : 80
  PD Power Draw       :   0 W +/- 6 W

switchA# show power-over-ethernet slot f

 Status and Counters - System Power Status for slot F

  Maximum Power       : 633 W           Operational Status  : On
  PSE Power Reserved  : 104 W           Usage Threshold (%) : 80
  PD Power Draw       :  95 W +/- 6 W​


    So can a single module actually handle 720 Watt of power if it needs to? Meaning: I can actually connect 24 access points that draw 30W on one module? Or is there a maximum per module, and I will have to spread the access points over multiple modules.

    Thanks in advance!

    Kind regards,
    Niels Mejan
    University of Twente


    (P.S. The question is for the purpose of getting the answer. I will be spreading the access points over various switches and modules anyway so I can make the cabling of the switch look nice too. This is a "patch once, don't touch it" situation for ~7 years with 115 access points per rack. Since we use 1100 Watt PSU's that have 900 Watt for PoE available each rack will have 2 switches, and each switch has 4 modules, so in the end it is ~15 access points per module.)

    ------------------------------
    Niels Mejan
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  • 2.  RE: Power specifications 5400R-zl2 modules

    Posted Jan 20, 2022 06:30 AM
    Hi!

    Each PoE+ can supply all the power required by PD but the focus should be on the Power Supply (Power Supplies) used, on a Aruba 5406R zl2 chassis (it can be equipped with a maximum of two PSU) you will face these scenarios:

    • Two PSUs: 2 x J9828A can provide up to 513 W
    • Two PSUs: 2 x J9829A can provide up to 1680 W
    • Two PSUs: 2 x J9830A can provide up to 4668 W
    Mixing of different power supply SKUs on the very same chassis is supported but not recommended and you will face these scenarios:

    • Two PSUs: 1 x J9828A + 1 x J9829A can provide up to 1074 W
    • Two PSUs: 1 x J9828A + 1 x J9830A can provide up to 2509 W
    • Two PSUs: 1 x J9829A + 1 x J9830A can provide up to 3116 W
    Clearly, considering the PS Redundancy mode (Full) running when you have two PSUs, if a PSU fails the total power supplied in case of failure will be the half of the value you have with two PSUs.

    Side note:

    All three PSUs J9828A, J9829A and J9830A support POE+power, if more than one PSU is connected, they provide 92.5% of the total power:

    • J9828A provides a maximum of 254W of PoE/PoE+ power (92.5% of 275W)
    • J9829A provides a maximum of 832W of PoE/PoE+ power (92.5% of 900W)
    • J9830A provides a maximum of 2312W of PoE/PoE+ power (92.5% of 2500W)
    Thus two J9828A are able to provide a maximum of 508W of PoE/PoE+ power (92.5% of 550W).

    All the system power usage for the blades takes precedence and the remainder power is given to the PoE+ pool.
    So to answer your initial question: "So can a single module actually handle 720 Watt of power if it needs to? Meaning: I can actually connect 24 access points that draw 30W on one module?" I believe that the answer - if I'm not mistaken - should be "Yes, provided that you have proper PSUs installed on the chassis to sustain such power draw" (also considering the Power Redundancy that came with usage of two PSUs instead of just one PSU).

    So to deliver an output of 720W to - say - 24 PDs connected to an     Aruba 24-port 10/100/1000BASE-T PoE+ MACsec v3 zl2 (J9986A) module (and considering each PD requiring exactly 30W) then the 6 slots chassis of your Aruba 5406R zl2 must be equipped with one (no PS Redundancy) or two (Full PS Redundancy) J9829A PSUs, if I've read correctly the documentation about PoE/PoE+ planning. The  J9829A PSU indeed provides up to 900W of PoE power, two J9829A can supply up to 1680W.

    The rule is that each chassis provisions (allocates power to) ports 1-24 of each module with the watts associated with the specific power supply unit(s) installed.

    ------------------------------
    Davide Poletto
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    Original Message


  • 3.  RE: Power specifications 5400R-zl2 modules
    Best Answer

    Posted Jan 20, 2022 06:53 AM
    Hello Niels,

    Did you already have a look at the Power over Ethernet (PoE/PoE+) Planning and Implementation Guide (ArubaOS-Switch)?
    Can be found on https://asp.arubanetworks.com
    direct link:
    https://support.hpe.com/hpesc/public/docDisplay?docId=c04344559

    few things to consider in the configuration POE+ redundancy or no redundancy when deploying two PSUs



    Original Message


  • 4.  RE: Power specifications 5400R-zl2 modules

    Posted Jan 20, 2022 11:42 AM
    Hello Parnassus, Sietze,

    Sadly I can only make one "Best answer" but kudo's to you both. The extract of Parnassus is what is described in the "Power over Ethernet (PoE/PoE+) Planning and Implementation Guide (ArubaOS-Switch)" documentation Sietze mentioned. I was not aware of that specific document but that's nicely documented. As you both mention it's all to do with the PSU's used what is possible, but individually each module itself can provide the full PoE+ power budget of 24 x 30 Watt.

    Kind regards,
    Niels Mejan
    University of Twente.

    ------------------------------
    Niels Mejan
    ------------------------------

    Original Message


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