2960-24PC-L PoE cable pairs

Unanswered Question
Mar 25th, 2008

Planning VoIP implementation on new 2960-24PC-L switches, using PoE for handsets. These switches will be dedicated VoIP network, no data. Because of physical wiring politics, would like to split pairs from existing Cat5e. From reading, it seems that modern 802.3af implementations use the data pairs for power, not requiring any spare pairs. Can anyone confirm that this is the case with the 2960-24PC-L? I would like to know if 2 pairs are enough for PoE here or whether we will need new drops.

Secondly, we will be using Polycom 501 handsets that seem to require special expensive "PoE cables" to work with many PoE switches and infusors. However, in some cases they work with standard patch cables, e.g. when using Foundry switches with loop detection mechanisms. Can anyone confirm whether the 2960-24PC-L switches would work without these special cables?


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Paolo Bevilacqua Tue, 03/25/2008 - 14:31

Hi, I have such a switch and I can tell you that like any other PoE works with the two data pairs only. What requires four pairs, is gigabit ethernet, you would not be able to use gigabit over wiring splitters.

About the polycom handsets, can you point us to some documentation about the special cables ? Again the 2960 PoE is like any other cisco PoE standard .3af and if something works with them will work work on the 2960.

thedealllc Tue, 03/25/2008 - 14:47

Thanks for the reply. My confusion was over documentation re midspan configs, where sometimes it uses two spare pairs for power. In any case, thanks for confirming re the two pairs only.

Re the Polycom, it seems the 501 phones are not internally PoE compatible without a special cable. We would need 550 phones for that. Oddly, some people claim that they have their working with specific switches, but in most cases it should not work. Nothing Cisco-specific it appears. We'll have to assume it won't work without the cables.

Thanks again for the reply!

Paolo Bevilacqua Tue, 03/25/2008 - 15:02

Hi, I don't know much you're committed already to that phone choice and the sip proxy that you're likely to use with it, but have you considered the cisco 7931G ?

- standard PoE

- backlighted display

- 24 lighted line buttons

- "hard" transfer, hold and other keys.

- full duplex speakerphone and dedicated headset socket

- SCCP only

- approx USD 35 less than the 501

Good luck!


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