Cisco 3750: Howto enable err-disabled ports

Personnel Reference Guide:

To enable err-disabled ports on Cisco 3750 switch series. Follow the below . . .

First make telnet connection with the switch

telnet 10.0.0.1

(change the ip as required,)
Enter Password to continue.

To view Disabled Ports:

show interfaces status err-disabled

e.g:

NOC_SWITCH>show int status err-disabled

Port      Name               Status                    Reason               Err-disabled Vlans
Gi2/0/10                     err-disabled         link-flap

NOC_SWITCH>

To Enable Port:

enable
config t
int G2/0/10
no switchport port-security  (< You probably dont need this line, its just to disable pot security feature, I used it to perform various tests)
shut
no shut
exit

Change the interface name to match your. In above example I had two 3750-e models in stack mode. so its showing G2, you may get G1 if you have single switch.

TIP:
Link flap means that the specific port continuously goes up and down. The port is put into the errdisabled state if it flaps more than four-five times in few seconds. The common cause of link flap is a Layer 1 issue such as a bad cable, duplex mismatch.

Regard’s
Syed Jahanzaib