Unable to use Power over Ethernet with a cisco 3500
Submitted by vrillusions on Tue, 11/20/2007 - 7:25am.
I have a Cisco 3500 XL switch that supports power over ethernet. We have a couple cisco ip phones and they run just fine. I plug in a gxp-2000 and nothing. It doesn't show it's connected on the switch or anything. Has anyone else had luck getting the 3500 switch to work or would I need something some special PoE switch? My other thought is these phones have run for months off a power adapter. Is there something I need to set so the grandstream knows to check for power over ethernet instead of trying to rely on the power adapter?
Would that be a 3524XL with Inline Power?
Tue, 11/20/2007 - 9:10am
Older Cisco "Inline Power" switches like the WS-C3524-PWR-XL-EN were designed before the 802.3af "Power over Ethernet" standard was finalized. As such it will ONLY work with Cisco phones and access points. Inline Power and PoE are 2 different animals.
Grandstream (and all other PoE devices) are designed to work with PoE switches or injectors.
Yep, that's exactly the
Tue, 11/20/2007 - 11:24am
Yep, that's exactly the model we're using. Had a feeling that may be the case since I had no idea till I saw the switch came with a couple cisco ip phones. Be more motivation to get cisco phones as the sound quality--especially the speakerphone--is much better than the grandstream. Thanks for the quick reply.
The issue is that switches
Wed, 11/21/2007 - 1:45pm
The issue is that switches talk via CDP with Cisco devices regarding inline power support. If a device can't talk CDP the switch doesn't enable inline power to protect his port from overload.
The only thing you can do is use inline power injectors. Even pre-AF Cisco Injectors work by changing the pin layout. While normally using a straight cable to connect a device to a switch port you just need to swap pin 4/5 with 7/8.
Switch ---Swap cable --- Cisco AF Injector --- Straight cable --- Grandstream
Swap Cable:
1-----1
2-----2
3-----3
4-----7
5-----8
6-----6
7-----4
8-----5
inaccuracy
Mon, 06/01/2009 - 1:45pm
"Inline Power and PoE are 2 different animals."
not to be nit-picky but: Inline Power is PoE. I think what you meant to say is: Inline Power PoE and 802.3af(industry standard) PoE are two different animals.
Power over ethernet is just a generic term to describe supplying power through an ethernet cable. Inline is pre-IEEE standared Power over Ethernet and still qualifies as PoE, just a different flavor. This is similar to the way that 802.3at is/will be considered PoE.
Great post, I just thought I'd throw that out there.
vrillusions
Fri, 06/19/2009 - 4:42pm
Hi vrillusions,
You have a WS-C3524-PWR-XL-EN right? Can you please tell me the model number of the power adaptor for that switch?
I have been looking and can't find the part number for the adaptor providing the POE...
By the way we have Linksys/CISCO SPA942 phones and they are CDP (Cisco Discovery Protocol) compliant. They are priced right and work well in case you buy more phones...
Thanks!
Member Since:
2007-07-16