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MAC flaps on cisco switch connected to ASA 5520

Network is something like this..


MPLS router1-------MPLS router2

        |                               |

MPLS switch1-------MPLS switch2

        |                               |

ASA-Primary---------ASA Secondary 



ASA secondary is active and primary is standby.

MPLS switch1 and switch2 are L2 switch running STP with port fast enabled. All ports part of VLAN 100 and MPLSswitch1 and MPLSswitch2 connected trunk etherchannel.

MPLS switch1 interface gi1/0/1 is connected to MPLS router1 on interface with MAC  "MAC-router1"

MPLS swtich1 interface gi1/0/3 is connected to ASA-Primary.


Now problem is when I disconnected the link between MPLS switch1 and ASA primary and connect back, there are intermittent ping drops from MPLS router1 to ASA primary and ASA secondary, although MPLSswitch2 to ASA secondary link is not touched.

For the link disconnection window, there are no logs on MPLSswitch2 but on MPLSswitch1 it says:

""%SW_MATM-4-MACFLAP_NOTIF: Host MAC-router1 in vlan 100 is flapping between port Gi1/0/3 and port Gi1/0/1""


Now this flap should not happen as the MAC-router1 should never appear on Gi1/0/3 of MPLS switch1.

Can anyone explain me the reason for such flap on MPLS switch1. And also the reason why there were ping drops to ASAsecondary when it was not even touched.


Everyone's tags (1)

Hellois there an active


is there an active/standby state change in ASA while you disconnect the link ? are you running HSRP on MPLS routers ?

Just take the show mac-address table address <MAC-router1) before and during the incident





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