[c-nsp] 3560g PoE issue

[Jay Hennigan]

Nilesh Sawant wrote:
> Hi,
> 
> I am observing the problem with 48 ports 3560G in LAN infrastructure. We have alcatel IP phone which are connected to 3560G switches. Sometimes these IP phone are not getting power up , after restarting the switch IP phone gets power up. As per cisco theory it's deliver average 7.7w on all 48 ports or 15.4 w on 24 ports.
> 
> i tried shut, no shut after IP phones gets power down, also tries to allocate 10-14w power on that particular interface, but no use.
> 
> What could be the issue ?

Not sure about Alcatel, but we have seen a similar issue with some 
Polycom phones.  The Polycom phones have the capability of adding 
"sidecar" units with additional display and buttons for DSS/BLF and the 
like.

Even with no sidecars installed, the phones default to having the 
sidecar power enabled and as such request the full 15.4 watts from the 
switch.  The Cisco switch will detect the requested power as 15.4 and 
deny power to additional phones once the aggregate power limit is 
reached based on this calculation.

A configuration setting on the phone allows one to disable sidecar power 
and once this is done the phone requests a more reasonable six watts. 
In this mode all ports can be used.

Keep in mind that TTBOMK power calculations in the switch are done by 
layer 2 messages indicating desired power from the connected device and 
not by an ammeter in the switch measuring actual power consumption.

Check your Alcatel phones and see if they are capable of powering 
accessories that you aren't using.  If so and you can disable this 
capability the phones may then negotiate with the switch to deliver less 
power and allow the use of more/all ports.

--
Jay Hennigan - CCIE #7880 - Network Engineering - jay at impulse.net
Impulse Internet Service  -  http://www.impulse.net/
Your local telephone and internet company - 805 884-6323 - WB6RDV