Time-Based PoE using EEM

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Jun 25th, 2008
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Hi Guys,

I'm really interested in getting an idea of how to use EEM Tcl scripts or other method to get PoE for our phones switched off at night to save power. Does anyone know if there's any whitepapers on doing this? I saw the idea on a Cisco slide already and have searched real hard to find a solution but to no avail. All I'm after is PoE being switched off on a port range between 19:00 and 06:00 simple as that!


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paolo bevilacqua Wed, 06/25/2008 - 02:03
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I'm not sure that you will save much power if any at all.

Due to the nature of the power supplies used, absorbtion on mains is not linearly proportional to the number of phones connected.

You can have an electrician measure it, with and without the PoE enabled, then judge yourself if it is worth to do that or not.

paulkbeyer Wed, 06/25/2008 - 02:20
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Hi buddy,

I'm curious why Cisco pimped the idea as a way of being more power efficient if the power supply is pulling constant power regardless of PoE usage. I hope this isn't a case of 'jumping on the green bandwagon' from Cisco. It'd be dissapointing if it is.

I've got a spare 3560PoE switch kicking around so I can power that up - monitor it, then run round to our production switches which are fully PoE enabled and used, then compare the two power consumption results. In the meantime - if anyone does now how to do this using EEM then please post as I'd like to provide the option should my test prove useful. I'll also post my power consumption results for everyones benefit.


paolo bevilacqua Wed, 06/25/2008 - 03:27
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Hi, EEM has a dedicated area on CCO where scripts are collected and discussed I think.

There are also a pair of whitepapers on the subject on CCO.

You can also find that it's easier to use some scripting on a PC based on "expect" that telnet to the switch and issues the commands based on a schedule.

andym1iptech Wed, 06/25/2008 - 06:21
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I can see one problem with this.

What happens if, after the phones are powered off, someone is stuck in the building or their is a fire how do they call anyone ?

Tommer Catlin Wed, 06/25/2008 - 07:36
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Yup! And the script does not run for some reason to turn on the phones in the morning. Business is down. How much does that cost per minute of downtime vs how much you are actually saving on your power bill vs "green marketing" material for your enterprise?




Those are my three. Turning off POE would be great. But safety. Having the screens go blank like a screen saver, much better. They would draw less power from the switch. (assuming)


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