I got a report that all our VoIP phone were down in a particular area that were connected to a Cisco 2960 switch. Upon investigation,
Initially, I ran the following show commands to check the status of the ports and power:
show power inline
The switch output:
It was indicating that there was no device drawing power from the switch which was strange because there were VoIP phones connected to this switch.
With further checks, I came across these errors in the event logs:
This error was telling me either the switch power module failed or some device caused a surge in power that causes the port power module to overload.
My resolution: Restart the switch which restored the switch to normal operations.
Being curious about the error, I researched it and came across this Cisco report:
https://quickview.cloudapps.cisco.com/quickview/bug/CSCsw18530
It was stating that this error is due to a bug in a particular version of IOS for 2960 switches.
The solution is:
Workaround:
Longer cable (>50ft) seems to fix the issue in most cases.
Solution
This issue is fixed in 12,2(55)SE3 , 12.2(58)SE1 and later releases. The
following interface configuration commands have to be applied to resolve the
issue,Switch(config)# int x/y
Switch(config-if)# power inline port 2x-mode
Switch(config-if)# shut
Switch(config-if)# no shutThe fix is present in the following platforms :
3750-E,3560-E, 3750-X, 3560-X, 3560-C, 2960S, 2960,2960C,2960X
The other platforms do not support 2X power mode and the workaround would be to
use a longer cable.
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