PoE power issue with 5312/5212's

[Devolution]

Hi Guys,

Have any of you experienced a problem with 5312/5212's not working because they are drawing too much power from the PoE switch?

The switch port is showing 7Watts is being drawn rather than the 4.7/4.2W that is needed. The only way to get the phone working again is to reset the switch port.

Could a power surge cause this problem? The network guys have washed their hands of it claiming it is the handset at fault.

System spec:
Mitel MXe Server with Mxe trunking gateway ver 4.1
Cisco 3750 switch.

Cheers.

 

[dryaquaman]

What PoE switch are you using?
If I remember right, in the cisco, you can limit the power to each port.

Ralph

 

[Devolution]

The customer uses Cisco 3750's and the switch port is limited to 7W. I have found that the switch port will show this figure only and not the actual amount of power being used so this is not helpful.
I have also found that there might have been a power surge around the time these problems started occurring so I'm putting my money on this.

 

[LoopyLou]

Are 7 watts really being drawn or does the Cisco think that it has to supply 7 Watts?

There may be no i in team but there are three f's in fudge off.

 

[Devolution]

7 Watts is the maximum a device attached can draw. If it has to provide any more, it will lock up. There is no way of seeing what the actual amount being drawn is on the cisco switch.
The phones all have PCs attached and the PCs were unaffected. The phones are dead but the PC's still worked.

 

[stsguy]

put a -power brick on 1 of the phones, if it stays up it's not the phone

 

[LoopyLou]

Either the Cisco is misreading what is sent by the Mitel phones or the phones are transmitting wrong values. Do you have other Mitel phones working or is it only 5312/5212 sets?

There may be no i in team but there are three f's in fudge off.

 

[JimHilton]

As a prove out, you could make yourself a spiffy cable where you could an amp meter inline get the current draw. Then use Ohms law to learn what the real wattage consumption is.

Also did the sets ever work with this switch or was it after the power surge they started flaking out?

 

[JimHilton]

Do you have the complete model number of that switch? It appears there are a couple that are not 802.3af capable.

Heres a link that if want to check it out:

http://www.cisco.com/en/US/prod/col...s5023/product_data_sheet09186a008016136f.html

 

[LoopyLou]

If the Cisco doesn't support 802.3af then the phones will have issues. Some older Cisco stuff did not support the standard.

There may be no i in team but there are three f's in fudge off.

 

[slapin]

Running Cisco 3750-48 PoE fully loaded with 52xx and 53xx phones without any issues. No limits specified.

Try to remove the limit and let switch auto-detect.

 

[Supernova99]

You could always invoke CDP (LLDP) as this will let the Cisco assign the exact power requirements. As a fully populated 3750 cannot provide enough power at 7 watts per port. Using CDP should ensure that all ports have the correct power settings and allow all ports to provide PoE

LoopyLou is correct about the 802.3af early Cisco switches had to have a power dongle to work correctly the 53xx series phones do not support the power dongle

Share what you know - Learn what you don't

 

[LoopyLou]

Agree with Supernova99. CDP is the way to go and that CDP is how the phones transmit their power requirements to the Cisco gear. Is CDP and option.

There may be no i in team but there are three f's in fudge off.

 

[Devolution]

I will get the IT guys to set this up on that switch to see if it helps. Certainly makes sense.
Haven't had any more issues since the original one, but then again there have not been any power disruptions /surges since.
I will keep you updated with my findings.
Cheers for the suggestions.

 

[LoopyLou]

It should help as part of CDP is that the phones tell the Cisco there power requirement on boot so even after a power disruption they would tell the Cisco what to supply when everything comes back up.

There may be no i in team but there are three f's in fudge off.