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host flapping between two ports ???

Below is a log show a host flapping between two port on a 3550;

%SW_MATM-4-MACFLAP_NOTIF: Host 0004.23d2.b0bc in vlan 2 is flapping between port Fa0/23 and port Fa0/11

%SW_MATM-4-MACFLAP_NOTIF: Host 0004.23d2.b0bc in vlan 2 is flapping between port Fa0/11 and port Fa0/23

Host 0004.23d2.b0bc is connect to port23, and port11 is a Dlink switch. Does that mean i have loop on the Dlink? I checked the dlink but did not find the loop cable. I clear the mac-table and ARP table, issue still exist.

switch is 3550, 12.2(35)SE. I found since I upgraded my 3550 this issue happened on many of my 3550. i did not notice before. is the issue with new IOS?

Thanks for advice.


Re: host flapping between two ports ???

Hi there,

If the message appears for multiple MAC addresses, the behavior is not normal. This behavior indicates a possible network problem because the MAC addresses move quickly from one port to another port before the default aging time. The problem can be looping traffic on the network, it has nothing to do with the upgrade you have done.

Kindly refer to the following link for troubleshooting steps:

HTH, please rate if it does help,

Mohammed Mahmoud.


Re: host flapping between two ports ???

Does the host only have one interface ?

Can it be a dual homing issue?