09-28-2011 01:59 AM - edited 03-07-2019 02:28 AM
Hi all,
Please waht'is the usefulness of "power inline consumption" command if poe requirement can be set with command 'power inline {auto [max milli-watts] | never | static [max milli-watts]}' ?
thanks a lot
ima
09-28-2011 05:00 AM
Hi,
There are two scenarios in which the Consumption Command Line Interface (CLI) can be used to manually configure the PoE allocation much more efficiently than the automatic algorithms:
++ Currently, the Cisco Catalyst 3750 Series budgets 15.4 W for Class 0 PDs. However, some of these PDs require a maximum of much less than 15.4 W (for example, the Siemens IP phone requires 5 W).
++ Without the Power Inline Consumption feature, customers could only deploy 24 of these devices. Customers can deploy up to 48 of these devices with the power inline consumption command for configuration of switchport power requirements.
++ Class 3 PDs are allocated 15.4W normally. Some IEEE Class 3 PDs (8-15 W range) use considerably less than 15.4 W maximum.
++ An example is the Avaya 2620SW, which uses 8W in the worst case scenario. If the Consumption CLI configured ports that support this phone to 8 W, a 3750-48PS could safely power 46 phones instead of 24.
++ Any misconfiguration on the switch (an over-subscription of the power supply) can reduce its reliability or damage the switch. If the power supply is over-subscribed by up to about 20 percent, the switch continues to operate but its reliability can be reduced. Above about 20 percent, the short-circuit protection circuitry triggers and shuts the switch down.
++ Issue the power inline consumption global or interface configuration command on the switch stack or on a standalone switch to override the amount of power specified by the IEEE classification for the device. Then, specify the wattage used by each powered device.
Hope this answers your question.
Cheers
Somu
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09-28-2011 05:58 AM
Hi Jayaraman,
thank u for your reply.
++ Without the Power Inline Consumption feature, customers could only deploy 24 of these devices. Customers can deploy up to 48 of these devices with the power inline consumption command for configuration of switchport power requirements.
this is the problem : we can limit the consumption by issuing ' power inline auto max milli-watts' without appling the power inline consumption command !! is it true ????
thx
ima
09-28-2011 06:31 AM
Hi,
By default, when the switch detects a powered device on an interface, it assumes the powered device consumes the maximum the port can provide (7 W on a legacy Power over Ethernet (PoE) module and 15.4W on the IEEE PoE modules introduced in Release 12.2(18)EW).
Then, when the switch receives a CDP packet from the powered device, the wattage automatically adjusts downward to the specific amount required by that device. Normally, this automatic adjustment works well, and no further configuration is required or recommended.
However, you can specify the powered device's consumption for the entire switch (or for a particular interface) to provide extra functionality from your switch. This is useful when CDP is disabled or not available.
When manually configuring the consumption for powered devices, you need to account for the power loss over the cable between the switch and the powered device
This link might interest you
-http://www.cisco.com/en/US/docs/switches/lan/catalyst4500/12.2/25ew/configuration/guide/PoE.html
Cheers
Somu
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