%PN-4-ERR_DISABLE: loopback error detected on GigabitEthernet1

[alok.sahu]

Hi,

I am facing issue on Cisco Switch 3850 , getting following message & port is getting disabled. Please help to sort out issue

%SW_MATH-4-MACFLAP_NOTIF : HOST in VLAN 3 is flapping between Port gi1/0/14 and port Gi1/0/23
%PN-4-ERR_DISABLE: loopback error detected on GigabitEthernet1/0/14 , putting Gi1/0/14 in err-disable state

[balaji.bandi]

A loopback error occurs when the keepalive packet is looped back to the port that sent the keepalive.

https://www.cisco.com/c/en/us/support/docs/lan-switching/spanning-tree-protocol/69980-errdisable-recovery.html

So suggest :

1. check any loops in the network.

2. check the cables.

3. what is the device connected to G /10/4 and G1/0/23 ?

4. post the configuration for more advise.

[Leo Laohoo]

Post the complete output to the command "sh interface Gi1/0/14" and "sh interface Gi 1/0/23".