Syed Jahanzaib Personal Blog to Share Knowledge !

December 7, 2012

Cisco 3750: Howto enable err-disabled ports

Filed under: Cisco Related — Tags: , , — Syed Jahanzaib / Pinochio~:) @ 2:09 PM

Personnel Reference Guide:


Errdisable is a feature that automatically disables a port on a Cisco Catalyst switch and is supported on most Catalyst switches running the Cisco IOS software.

The Errdisable error disable feature was designed to inform the administrator when there is a port problem or error.  The reasons a catalyst switch can go into Errdisable mode and shutdown a port are many and include:

  • Duplex Mismatch
  • Loopback Error
  • Link Flapping (up/down)
  • Port Security Violation
  • Broadcast Storms

When a port is in error-disabled state, it is effectively shut down and no traffic is sent or received on that port. The port LED is set to the orange color and, when you issue the show interfaces command, the port status shows as Errdisabled.

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

First make telnet connection with the switch


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

To view Disabled Ports:

show interfaces status err-disabled


NOC_SWITCH>show int status err-disabled

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


To Enable Port:

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)
no shut

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.

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.

For more detailed and brief descriptions, please visit

Syed Jahanzaib


  1. Hello,

    You don’t need to remove the port-security on the port. just shut the port and no shut it.

    config t
    int G2/0/10
    no shut

    Comment by Germain — December 7, 2012 @ 4:13 PM

    • Yes you really don’t need to disable port security, its good, but in my test lab I had to disable it to perform various tests.
      thanks for sharing.

      Comment by Syed Jahanzaib / Pinochio~:) — December 7, 2012 @ 8:33 PM

  2. […] 5. link-flap,这个大多是物理链路造成的 […]

    Pingback by channel-misconfig (STP) 分析防范 | Jasey Wang — March 11, 2013 @ 5:49 PM

  3. Hello Everyone Assalamu alikum, I have a new problem at hand. Recently i add a new Cisco Catalyst 2960 TCS with my network, Using Mikrotik CCR-1016 for Routing, When I add This new switch with mikrotik interface, getting some packet loss, Like If i ping my gateway its showing Replay from 2ms or sometime 30ms+, also miss 1 packet after 15-20 replay from gateway. I have another old Catalyst 2960TCL which is ok no ping loss from gateway, If i connect my new Catalyst 2960 with old Catalyst 2960TCL, then no packet loss also getting ping from gateway <1ms-2ms.
    From Mikrotik I connected to Giga Ethernet port to switch with Machine made Cable. In Mikrotik Auto Port Negotiation is on also selected 100 full, 1000full, I changed MSS in firewall.
    If i Reboot my Mikrotik or change port then there is no Ping loss or getting good ping time for only 5 minute then again its starts to loss after every 20 replay.
    Mikrotik Configuration: All user connect with DHCP, No Filter Rules, NAT set to Masquerade, In mangle only rules for FTP servers,
    Please Anyone solve this issue, Thanks in Advance.

    Comment by MD. Nahid — July 30, 2015 @ 3:59 PM

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