Cisco Support Community
Showing results for 
Search instead for 
Did you mean: 

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. And see here for current known issues.

New Member

C3750 PoE gives out not power until shut/no shut

I have deployed a new stack of five C3750-48 switches. This morning 11 ports on the first(Master) switch were down/down. When I plugged in a spare 7940 directly into the ports, to check the patch cabling, the phone did not power up. The port was down/down and no log was generated. When I plugged my laptop directly into the port I have network connectivity. If I then put the 7940 in, it still didnt power on. The only way to restore power was to do a shut/no shut on the effected interfaces and then the phones worked.

What on earth is going on?

I also saw the switch shut down a couple of ports with 7940's on them due to a BPDU guard error. However this wasnt on all the ports that didnt get power, so I have posted another conversation.

Cisco Employee

Re: C3750 PoE gives out not power until shut/no shut

It would always help to inlude the IOS version. I found few bugs related to inline power.

This one was for 3560 but the architecture is similar to 3750

Check to see if the IOS you are running is past these bugs and if its not, consider getting past it.

For the other issue with BPDU guard, the switch would shut down the port if it receives BPDU on a portfast enabled port. If you are sure nobody connected another switch to the port, I have seen Windows XP PCs with integrated NIC and wireless card send out BPDUs since they are bridging capable. See if this is the case.

New Member

Re: C3750 PoE gives out not power until shut/no shut

I am using 12.2(25)SEB4. I will take a look, thanks.

CreatePlease login to create content