I have a problem.
I have a Cisco 2960, this switch conect 23 Macs. The problem is that a pc puts the port in err-disable.
When I put the command "show interfaces status err-disabled" the output is this:
Port Name Status Reason Err-disabled Vlans Fa0/23 err-disabled loopback Fa0/24 err-disabled loopback
First it happened with the 23, I changed the machine to 24 and after several hours the same thing.
They only mention this:
A loopback error occurs when the keepalive packet is looped back to the port that sent the keepalive. The switch sends keepalives out all the interfaces by default. A device can loop the packets back to the source interface, which usually occurs because there is a logical loop in the network that the spanning tree has not blocked. The source interface receives the keepalive packet that it sent out, and the switch disables the interface (errdisable). This message occurs because the keepalive packet is looped back to the port that sent the keepalive:
%PM-4-ERR_DISABLE: loopback error detected on Gi4/1, putting Gi4/1 in err-disable state
Keepalives are sent on all interfaces by default in Cisco IOS Software Release 12.1EA-based software. In Cisco IOS Software Release 12.2SE-based software and later, keepalives are not sent by default on fiber and uplink interfaces. For more information, refer to Cisco bug ID CSCea46385 (registered customers only) .
The suggested workaround is to disable keepalives and upgrade to Cisco IOS Software Release 12.2SE or later.
Can someone help me? Please.