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New Member

IP Phone issue on 3750. Network dies when 28th Phone is plugged in!!!!

Hi, I am currently trying to resolve a issue i have with 2, 3750's which are stacked together. I currently have 27 Cisco IP PoE Phones plugged in across both switches, (18 on Master, 9 on Slave) models are both 7940's and 7960's. However when I plug in a 28th phone, the network dies, all the PC's and phones (other than the one just plugged in) reset and lose their connections, and will not come back until the 28th phone is unplugged. However if i remove one phone, and then re-plug another phone in, everything is fine. Below are some tests that i performed to find out if it was a PoE issue on the switches.

When i say PoE was Disabled, i mean i had turned the power inline to never, and had the phone powered by the AC Adapter.

Had 27 phones plugged in, plugged in number 28 with PoE enabled = Network Dies

Had 27 phones plugged in, plugged in number 28 with PoE DISABLED = Network Dies

Had 26 phones plugged in, plugged in number 27 with PoE enabled = Network stays active

Had 26 phones plugged in, plugged in number 27 with PoE DISABLED = Network stays active

Also, when i issue the sh power inline command it tells me following:

Module Available Used Remaining

(Watts) (Watts) (Watts)

------ --------- -------- ---------

1 370.0 113.4 256.6

2 370.0 56.7 313.3

On the 3750's i am running C3750-IPSERVICESK9-M Version 12.2(25)SED1 IOS.

Any help is greatly appreciated, thanks for the help in advance.

Regards,

Robert N.

CCNA.

2 REPLIES
Bronze

Re: IP Phone issue on 3750. Network dies when 28th Phone is plug

Bizarre. Turn the logging up to debugging and rerun those tests.

New Member

Re: IP Phone issue on 3750. Network dies when 28th Phone is plug

Ok, well this is another twist. Turned on logging and nothing to exciting turned up. Went to that office after hours to try and force the network down, however no matter how many phones i plugged in, nothing would happen (plugged in 6 phones, 7940's, 7960's 7912's)... So my thoughts are it may be the Gbit link we have from this office to our Co-Location, so i have set up some MRTG graphs to help try and find out if it is the link under intense strain.

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