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3750 flapping messages

Hi,

I have two Cisco Catalyst 3750-48-TS-E stacked for 2 years. Today, it started showing this logs....

%SW_MATM-4-MACFLAP_NOTIF: Host 0000.0000.fe00 in vlan 120 is flapping between port Fa2/0/20 and port Fa1/0/20

%SW_MATM-4-MACFLAP_NOTIF: Host 0000.0000.fe01 in vlan 120 is flapping between port Fa1/0/20 and port Fa2/0/20

%SW_MATM-4-MACFLAP_NOTIF: Host 0000.0000.fe00 in vlan 120 is flapping between port Fa2/0/20 and port Fa1/0/20

%SW_MATM-4-MACFLAP_NOTIF: Host 0000.0000.fe00 in vlan 120 is flapping between port Fa1/0/20 and port Fa2/0/20

%SW_MATM-4-MACFLAP_NOTIF: Host 0000.0000.fe01 in vlan 120 is flapping between port Fa1/0/20 and port Fa2/0/20

%SW_MATM-4-MACFLAP_NOTIF: Host 0000.0000.fe00 in vlan 120 is flapping between port Fa1/0/20 and port Fa2/0/20

%SW_MATM-4-MACFLAP_NOTIF: Host 0000.0000.fe01 in vlan 120 is flapping between port Fa1/0/20 and port Fa2/0/20

%SW_MATM-4-MACFLAP_NOTIF: Host 0000.0000.fe01 in vlan 120 is flapping between port Fa2/0/20 and port Fa1/0/20

%SW_MATM-4-MACFLAP_NOTIF: Host 0000.0000.fe00 in vlan 120 is flapping between port Fa2/0/20 and port Fa1/0/20

%SW_MATM-4-MACFLAP_NOTIF: Host 0000.0000.fe01 in vlan 120 is flapping between port Fa2/0/20 and port Fa1/0/20

%SW_MATM-4-MACFLAP_NOTIF: Host 0000.0000.fe00 in vlan 120 is flapping between port Fa2/0/20 and port Fa1/0/20

"show arp" doesn't show those two MAC.

Any idea what causing this?

Thanks,

Dandy

  • LAN Switching and Routing
6 REPLIES
Bronze

Re: 3750 flapping messages

It sounds like a layer2 loop. You might want to shutdown one interface and check your config.

Bronze

Re: 3750 flapping messages

From Cisco site:

"Error Message SW_MATM-4-MACFLAP_NOTIF: Host [enet] in [chars] [dec] is flapping

between port [chars] and port [chars]

--------------------------------------------------------------------------------

Note This message applies to Catalyst 3750 and 3560 switches.

--------------------------------------------------------------------------------

Recommended Action The switch found the traffic from the specified host flapping between the specified ports. [enet] is the host MAC address, [chars] [dec] is the switch ID, the first and second [chars] are the ports between which the host traffic is flapping.

Recommended Action Check the network switches for misconfigurations that might cause a data-forwarding loop."

Hall of Fame Super Silver

Re: 3750 flapping messages

Hello Dandy,

verify if on the two ports f1/0/20 and f2/0/20 a server with multiple NICs is connected.

They may have changed the configuration on their side to active/active.

This would require an etherchannel to be handled correctly by the switch.

Hope to help

Giuseppe

Re: 3750 flapping messages

Hi Giuseppe,

The connected device is Firewall (HA). I'm still checking with the customer what type of firewall and whether it active/active or active/passive.

Regards,

Dandy

New Member

3750 flapping messages

Hi,

This indicates that FW cluster is sending hearbit on this VLAN. If you observe high CPU on switch or if you have other traffic on same VLAN, you should consider shifting hearbit on dedicated LAN/cable. It may cause impact if your traffic increases.

Hall of Fame Super Gold

3750 flapping messages

I agree with Giuseppe's recommendation, you only get this type of error message if etherchannel is not setup correctly.

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