EX2300-C-12P PoE issues

[Richard McGovern]

Chris what is actually happening here is not so much class setting but LLDP/LLDP MED.  By default EX switches support LLDP MED POE-Negotiation, and use this method 1st.  So whatever wattage the external device requests is taken into the total power budget.  Once the switch calculation for these reaches max POE for the switch, no additional POE power will be provided.  This is even if the device pulls much less power than it negotiated for or asked for.  The switch needs to reserve that power calculation as a 'just in case'.  We actually reserve more than the value with LLDP MED tlv, to account for potential cable loss; this is approximately 10% more.

So if you disable LLDP MED, then class value will take over, and there is no need to set static.  Of course setting static is always an option, and if set that value is used regardless of other settings.

FYI only, Rich

Richard McGovern
Sr Sales Engineer, Juniper Networks 
978-618-3342
 
I’d rather be lucky than good, as I know I am not good
I don’t make the news, I just report it
 

On 9/5/19, 8:49 PM, "Chris Lee" <chris at datachaos.com.au> wrote:

    For the benefit of the archives have found a solution for this, it appears
    to come down to power budgets and defaults of class based PoE management.
    Have never noticed this before as on all our 24-port EX2300 and 48-port
    EX3400 and 4300's there's always at least sufficient total power budget to
    allocate 15.4 watts across every interface.
    
    So class 3 devices allocated 15.4watts of power theoretically means you
    could effectively only have 9x class 3 ports power up with a total of 138.6
    watts, unfortunately I currently don't have enough class 3 PoE devices in
    the lab to fully test this theory, and what I saw in the field was the
    switch would only provide power to the first 7x ports even though there was
    still sufficient power remaining to allocate 2x more ports, maybe it's
    something to do with internal power bank architecture/design or additional
    power reserves per class 3 device.
    
    The workaround was to define PoE management type as static and set max
    power for all interfaces to 12 watts, and then the remaining cameras
    interfaces ge-0/0/7 to 9 that previously wouldn't power up all started fine
    and are online. Note there's a bit of lag even after committing the
    configuration, seems to take a minute or two for the config change to flow
    onto the PoE controller and reflect the change from class to static
    management with max power of 12 watts defined.
    
    z at z> show configuration poe
    management static;
    interface all {
        maximum-power 12;
    }
    
    Regards,
    Chris
    
    On Thu, Sep 5, 2019 at 8:34 PM Chris Lee <chris at datachaos.com.au> wrote:
    
    > Hi,
    >
    > Wondering if anyone is successfully running EX2300-C-12P switches with at
    > least 8x PoE devices connected ?
    >
    > We've just encountered an issue in the last week across 2 of these
    > switches at different locations with around 10x PoE CCTV cameras connected,
    > and only the first 7 ports (ge-0/0/0 to ge-0/0/6) providing PoE power.
    >
    > One switch is running JUNOS 15.1X53-D591.1 and the other is JUNOS
    > 18.1R3-S7.1.
    >
    > Both have had the PoE firmware controller update done on them that comes
    > with releases beyond 15.1X53-D58 I think it was, which when you look at
    > firmware detail the PoE version on chassis is  2.1.1.19.3
    >
    > I have an active JTAC case open for it, I've done PR Search and can't see
    > anything against POE or Power for either of those two releases that relate
    > to the EX2300/3400 series.
    >
    > In both cases the PoE cameras on the end of the line are very low power
    > bullet / fixed style cameras only drawing around 3 watts each, and the most
    > I've seen reported on show poe controller is around 25 watts power draw
    > which is no where near the EX2300-C-12Ps max power budget of 146watts.
    >
    > If I deliberately disable PoE on an interface like ge-0/0/0, then after a
    > minute or so interface ge-0/0/7 will then magically start providing power,
    > and as soon as I rollback the config and commit it will revert right back
    > to port ge-0/0/7 providing no power, and ge-0/0/0 powering up.
    >
    > Thanks,
    > Chris
    >