Working out available power for phones

[GRANT3779]

Hi,

Is there some sort of rule of thumb to follow when working out how many phones you will be able to power on a switch? e.g If I have a stack of  4 x 3750X how do you work out available power for phones? Does it make a difference if the switches run dual PSU etc.. and is there a drop in the available power if a switch loses it's main power and depends on STACK power etc..

Any further info would be appreciated.

Thanks

[Brandon Pierce]

Use the show inline power (or is it power inline.... can never remember) command to see how much each phone is soaking up.  Some phones use more than others if they have the color LCD screen and such.  They all start at 15.4 and then drop to what they need from there.

[GRANT3779]

Hi Brandon,

It was more of how to work out how much power I'd have available before I bought the switches, e.g If I was to buy 5 x 3750x POE, how much POE would be available.

I know how to view the available power on currently owned switches. It was really just to try and work out what I'd have "IF" I purchase this and that. This would then steer me in the direction of what I should buy if I have for example 300 7940G phones for example and 7 APs.

Thanks

[Brandon Pierce]

Also, I dont know about the newer switches as I haven't really messed with them yet but on the older ones you couldn't use anymore than half the ports for PoE with the base power supply unless you upgraded.

[Rob Huffman · Accepted solution]

Hi there,

In addition to the good tips from Brandon (+5) you may want to check out the Cisco Power Calculator tool which is perfect for this type of query.

http://tools.cisco.com/cpc/

Cheers!

Rob