cancel
Showing results for 
Search instead for 
Did you mean: 
cancel
415
Views
0
Helpful
2
Replies

C3750 PoE gives out not power until shut/no shut

Nicholas Poole
Level 1
Level 1

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.

2 Replies 2

Prashanth Krishnappa
Cisco Employee
Cisco Employee

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

http://www.cisco.com/cgi-bin/bugtool/onebug.pl?bugid=CSCeg10954

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

http://www.cisco.com/cgi-bin/bugtool/onebug.pl?bugid=CSCsc10999

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.

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

Getting Started

Find answers to your questions by entering keywords or phrases in the Search bar above. New here? Use these resources to familiarize yourself with the community: