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Author Topic: Failure of POE on BS460/470's  (Read 2498 times)

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Offline pat2012

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Failure of POE on BS460/470's
« on: July 14, 2013, 02:52:28 PM »
Hi folks.

We've been using VoIP for several years at many sites/buildings.  Over these years we've been having too many instances of BS 460's and 470's POE failing. In some cases the individual ports would fail (no longer able to properly power up IP phones). The techs would simply move to a next port.

In other cases, the entire POE on the switch would fail with no chance of recovery. The POE power utilisation is never even close to the limit of the switch/port.

We have a mix of i2000's and 1100 phones.

In some cases the ports would no longer be able to forward traffic and are deemed "bad ports". Resetting doesn't help.

I want to believe that there is some electrical problem that is causing these failures.  Like I said, we have VoIP in many buildings - some buildings have no issues while others have more instances of POE failure.

We have in the past suspected poor electrical grounding in the buildings.  Most of our switches are protected by online Powerware UPSes.  But that is no protection against bad grounding, especially at the phones/PCs.

Is there anything else we should be looking at?  I admit this issue is more electrical in nature.  How can I determine what is causing the POE failures?  There has to be something that is causing the POE to fail.

Have any of you experienced unusually high rates of POE port failures with the 460/470's?

Can poor cabling also be a contributing factor?  Excessive Electrical interference inducing high currents in the UTP cable, maybe?  Is there a way to test that?

I'm also thinking we need to go on a massive equipment cabinet grounding program.  But what if the switch is not installed in a rack or cabinet?  There is nothing to ground!

We've recently deployed some ERS 4000's and so far I haven't gotten any reports of POE issues - knock on wood.....


Offline TankII

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Re: Failure of POE on BS460/470's
« Reply #1 on: July 16, 2013, 01:04:10 PM »
POE needs:
Properly grounded racks - Which, BTW, is the national code requirement
On-Line Double-Conversion UPS' - Line interactive units don't hold up so well with the POE midplanes

460's and 470's have POE firmware available.  Verify you have it on the boxes, along with the latest diags and software.

Other notes:
Put your switches in pure 802.3af mode rather than support legacy.
Verify your patch cords are not on the 'wanted' list for faulty conductors with improper coatings.  It could cause corrosion of the individual switch ports.  There have been multiple recalls of cables, ends, and patch cords that are not meeting the standards but have labels stating they do.  The problem is getting quite severe in the industry the past three years.  BTW, this does not even include those knockoffs that keep showing up all the time.


Offline Michael McNamara

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Re: Failure of POE on BS460/470's
« Reply #2 on: July 17, 2013, 09:22:38 AM »
We've experienced the same high failure rate on the BayStack 460. I originally suspected the heat in our closets had something do-to with it but eventually we started having problems in closets with no cooling issues.

Thankfully we've replaced most of those switches over the years through consolidation and other projects.

The ports would generally work but they wouldn't provide PoE...only had a handful of 470s which were PoE capable so I can't speak to those... the regular 470s were work horses for us and served us well - those are also being phased out there days for the ERS 5520 and ERS 4850.

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