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I've noticed that quite a many VOIP phones support PoE. While the idea seems great in principle (no worrying about power adapters anywhere), have you found it to be effective for enterprise-wide deployment?

My main concern is that all switches need to support PoE: so far as I can tell, plugging in a non-PoE switch in front of a PoE switch will mean that all devices under the non-PoE will not have power. Because PoE switches are quite a bit more expensive than non-PoE, and with PoE standards changing, this seems like it could be a dodgy investment.

That, and if you want users to take their VOIP phones on the road, then they'll need to remember to pick up an adapter or injector, and figure out how to hook it all together.

Is PoE better for point-to-point applications, such as running a WAP in some remote place that's not powered? Or, is it effective at the enterprise level?

Dennis Williamson
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Alex Papadimoulis
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4 Answers4

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I don't know about the standards changing for PoE, haven't heard of any issues there. We run many Cisco VOIP phones and while we do have some issues (the phones are basically computers; they do lock up and resetting them is a matter of unplugging and plugging them back in) we haven't have direct issues due to PoE.

If you don't have PoE switches you have to plug in a power injector or a power adapter on the phone.

Taking VOIP phones...on the road? These are desktop phones, usually. I mean...do you have a lot of people taking their desktop phones with them on the road? If it's a portable phone, it's already got mechanisms for being carried...just like you already would have to do. Or they use cell phones.

PoE does work well for remote WAPs as well since you can reset them at the switch and it's less cabling (just ethernet instead of ethernet plus power).

I'd say that yes...it is effective at the enterprise level and investing in PoE switches is no more dodgy than installing any other technology available today.

Bart Silverstrim
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  • Well put. For phones on the road, I was thinking more like extended trips or working from home situation... not like an overnight thing. – Alex Papadimoulis Sep 15 '09 at 14:15
  • They'd have to have access to your network in order for the VOIP to work, though. That's why it's kind of unusual to go through the trouble of VPN'ing remote sites for phones at homes when most go with corporate cells or something like that...less of a security risk. – Bart Silverstrim Sep 15 '09 at 14:17
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plugging in a non-PoE switch in front of a PoE switch will mean that all devices under the non-PoE will not have power

That ^^ would be correct.

PoE switches in the enterprise are really becoming the norm now, especially edge switches. The cost differences are pretty minimal at least with the big players like Cisco, HP, Extreme, etc.

WAPs, VOIP phones, server cameras, etc. can all benefit from the ease of PoE switch ports. Most switches that have it are "auto-sensing" and will automatically apply the power if needed.

I would say it is "more effective" at the enterprise level than elsewhere. Small deployments can get by with power bricks/adapters but for large scale it ends up being cheaper to go with PoE switches then to buy power bricks for every PoE device.

For VOIP phones on the road, yeah you'll need a power adapter, but usually it is easier to just use a softphone app on a laptop that connects over the web to the enterprise PBX (remember you were asking what enterprises do).

TheCleaner
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I've seen a lot of PoE switches powering thin-accesspoints for managed WLAN solutions (like Trapeze or Ruckus). Works like a charm and you only have to get a cat5/6 cable to the point where the access point will be located - no need to bother with power cords and such.

PoE itself (802.3af) is a well known standard and well implemented by the major networking hardware manufacturers. Never had any problems with it (speaking of several thousands of ports).

PEra
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3Com makes 'power injectors' that allow you to turn a switched port into a powered switch port. We use 4 of these for our PoE-based WiFi access points. Considerably cheaper than buying a switch with PoE based ports.

The injectors plug into wall power, and take a patch cable from the switch, and another cable out to the equipment that needs to be powered.

http://www.3com.com/products/en_US/detail.jsp?tab=prodspec&sku=3CNJPSE&pathtype=purchase

Dennis Wurster
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