Cisco 7937 conference phone doesn't power up on 3750 switches

[craig.juhas]

Hi,

I've recently come across a rather strange problem with connecting 7937 conference phones to our 3750 switches.

I connected it to port 48 on a switch and it powered on fine. However, if I connected it to another random port on the same switch nothing happened. I tried several other ports and it was the same affect. I tried using a different network cable and even a different 7937 but the result is the same - no power. The result is even the same on a different stack of 3750s.

On the port it does work on I can see it consumes 10.5 watts and the port has a capacity of 15 watts. So it's not overloading the ports. The switches I've been testing with have less than a dozen POE devices connected so the switch isn't overloaded either.

Does anyone have any ideas why a 7937 would power up in some ports and not others?

[andreas.klein]

Hi, PoE might be disabled on the other ports?

3560PoE(config-if)#power inline ?

auto Automatically detect and power inline devices

consumption Configure the inline device consumption

never Never apply inline power

static High priority inline power interface

Could you give us a complete SH POWER INLINE and a part of SH LOG when you connect it into one of the non fonctionning ports?

[craig.juhas]

Below is the power output:

DUK1LSW0005#sh power inline

Module Available Used Remaining

(Watts) (Watts) (Watts)

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

1 370.0 35.7 334.3

2 370.0 33.6 336.4

Interface Admin Oper Power Device Class Max

(Watts)

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

Gi1/0/1 auto off 0.0 n/a n/a 15.4

Gi1/0/2 auto off 0.0 n/a n/a 15.4

Gi1/0/3 auto off 0.0 n/a n/a 15.4

Gi1/0/4 auto off 0.0 n/a n/a 15.4

Gi1/0/5 auto off 0.0 n/a n/a 15.4

Gi1/0/6 auto off 0.0 n/a n/a 15.4

Gi1/0/7 auto off 0.0 n/a n/a 15.4

Gi1/0/8 auto off 0.0 n/a n/a 15.4

Gi1/0/9 auto off 0.0 n/a n/a 15.4

Gi1/0/10 auto off 0.0 n/a n/a 15.4

Gi1/0/11 auto off 0.0 n/a n/a 15.4

Gi1/0/12 auto off 0.0 n/a n/a 15.4

Gi1/0/13 auto off 0.0 n/a n/a 15.4

Gi1/0/14 auto off 0.0 n/a n/a 15.4

Gi1/0/15 auto off 0.0 n/a n/a 15.4

Gi1/0/16 auto off 0.0 n/a n/a 15.4

Gi1/0/17 auto off 0.0 n/a n/a 15.4

Gi1/0/18 auto off 0.0 n/a n/a 15.4

Gi1/0/19 auto off 0.0 n/a n/a 15.4

Gi1/0/20 auto off 0.0 n/a n/a 15.4

Gi1/0/21 auto off 0.0 n/a n/a 15.4

Gi1/0/22 auto off 0.0 n/a n/a 15.4

Gi1/0/23 auto off 0.0 n/a n/a 15.4

Gi1/0/24 auto off 0.0 n/a n/a 15.4

Gi1/0/25 auto off 0.0 n/a n/a 15.4

Gi1/0/26 auto on 6.3 IP Phone 7940 n/a 15.4

Gi1/0/27 auto off 0.0 n/a n/a 15.4

Gi1/0/28 auto off 0.0 n/a n/a 15.4

Gi1/0/29 auto off 0.0 n/a n/a 15.4

Gi1/0/30 auto off 0.0 n/a n/a 15.4

Gi1/0/31 auto off 0.0 n/a n/a 15.4

Gi1/0/32 auto off 0.0 n/a n/a 15.4

Gi1/0/33 auto off 0.0 n/a n/a 15.4

Gi1/0/34 auto off 0.0 n/a n/a 15.4

Gi1/0/35 auto off 0.0 n/a n/a 15.4

Gi1/0/36 auto off 0.0 n/a n/a 15.4

Gi1/0/37 auto on 6.3 IP Phone 7940 n/a 15.4

Gi1/0/38 auto off 0.0 n/a n/a 15.4

Gi1/0/39 auto on 6.3 IP Phone 7940 n/a 15.4

Gi1/0/40 auto off 0.0 n/a n/a 15.4

Gi1/0/41 auto off 0.0 n/a n/a 15.4

Gi1/0/42 auto on 6.3 IP Phone 7940 n/a 15.4

Gi1/0/43 auto off 0.0 n/a n/a 15.4

Gi1/0/44 auto off 0.0 n/a n/a 15.4

Gi1/0/45 auto off 0.0 n/a n/a 15.4

Gi1/0/46 auto off 0.0 n/a n/a 15.4

Gi1/0/47 auto off 0.0 n/a n/a 15.4

Gi1/0/48 auto on 10.5 IP Phone 7937 3 15.4

[craig.juhas]

...

[craig.juhas]

Gi2/0/1 auto off 0.0 n/a n/a 15.4

Gi2/0/2 auto off 0.0 n/a n/a 15.4

Gi2/0/3 auto off 0.0 n/a n/a 15.4

Gi2/0/4 auto off 0.0 n/a n/a 15.4

Gi2/0/5 auto off 0.0 n/a n/a 15.4

Gi2/0/6 auto off 0.0 n/a n/a 15.4

Gi2/0/7 auto off 0.0 n/a n/a 15.4

Gi2/0/8 auto off 0.0 n/a n/a 15.4

Gi2/0/9 auto off 0.0 n/a n/a 15.4

Gi2/0/10 auto on 10.5 IP Phone 7937 3 15.4

Gi2/0/11 auto off 0.0 n/a n/a 15.4

Gi2/0/12 auto off 0.0 n/a n/a 15.4

Gi2/0/13 auto off 0.0 n/a n/a 15.4

Gi2/0/14 auto on 10.5 IP Phone 7937 3 15.4

Gi2/0/15 auto on 6.3 IP Phone 7960 n/a 15.4

Gi2/0/16 auto on 6.3 IP Phone 7960 n/a 15.4

Gi2/0/17 auto off 0.0 n/a n/a 15.4

Gi2/0/18 auto off 0.0 n/a n/a 15.4

Gi2/0/19 auto off 0.0 n/a n/a 15.4

Gi2/0/20 auto off 0.0 n/a n/a 15.4

Gi2/0/21 auto off 0.0 n/a n/a 15.4

Gi2/0/22 auto off 0.0 n/a n/a 15.4

Gi2/0/23 auto off 0.0 n/a n/a 15.4

Gi2/0/24 auto off 0.0 n/a n/a 15.4

Gi2/0/25 auto off 0.0 n/a n/a 15.4

Gi2/0/26 auto off 0.0 n/a n/a 15.4

Gi2/0/27 auto off 0.0 n/a n/a 15.4

Gi2/0/28 auto off 0.0 n/a n/a 15.4

Gi2/0/29 auto off 0.0 n/a n/a 15.4

Gi2/0/30 auto off 0.0 n/a n/a 15.4

Gi2/0/31 auto off 0.0 n/a n/a 15.4

Gi2/0/32 auto off 0.0 n/a n/a 15.4

Gi2/0/33 auto off 0.0 n/a n/a 15.4

Gi2/0/34 auto off 0.0 n/a n/a 15.4

Gi2/0/35 auto off 0.0 n/a n/a 15.4

Gi2/0/36 auto off 0.0 n/a n/a 15.4

Gi2/0/37 auto off 0.0 n/a n/a 15.4

Gi2/0/38 auto off 0.0 n/a n/a 15.4

Gi2/0/39 auto off 0.0 n/a n/a 15.4

Gi2/0/40 auto off 0.0 n/a n/a 15.4

Gi2/0/41 auto off 0.0 n/a n/a 15.4

Gi2/0/42 auto off 0.0 n/a n/a 15.4

Gi2/0/43 auto off 0.0 n/a n/a 15.4

Gi2/0/44 auto off 0.0 n/a n/a 15.4

Gi2/0/45 auto off 0.0 n/a n/a 15.4

Gi2/0/46 auto off 0.0 n/a n/a 15.4

Gi2/0/47 auto off 0.0 n/a n/a 15.4

Gi2/0/48 auto off 0.0 n/a n/a 15.4

It's not worth showing the logs at the moment as there's another port that's filled up the buffer with flapping. I'll get the logs while connecting a 7937 next time I'm in front of those

[craig.juhas]

I've discovered a solution although I'm still not totally sure why it works. What I've had to do is plug a 7940 handset into the port first, which works, the disconnect 7940 and connect the 7937. It then powers up and works no problem. Odd!!