MAC address flapping between Cisco 3020 switch ports

[Harutyun Hakobyan]

Hi all,

On my two Cisco 3020 switches (please see attached pic) I see many syslog messages:

%SW_MATM-4-MACFLAP_NOTIF: Host MAC_ADDRESS_OF_SW3 in vlan 100 is flapping between port Gi0/21 and port Gi0/23

This interface flapping messages are for all vlans on both switches.

When I ping to Server, there are no timeouts and all ok.

This is config of Gi0/21 and Gi0/23 interfaces on both 3020:

!
interface GigabitEthernet0/21
 switchport mode trunk
!
interface GigabitEthernet0/23
 switchport mode trunk
 media-type internal
 spanning-tree link-type point-to-point
!

When I down internal link Gi0/23, connection to Server is lost.

So what is right configuration for my topology ?

Thanks

[Madhukrishnan Gopinathan Nair]

Is the server dual homes to both these ports?

Thanks,

Madhu.

[Harutyun Hakobyan]

Server has two ethernet ports from which created Team interface.

One ethernet port connected to C3020_SW1, another to C3020_SW2.

[Madhukrishnan Gopinathan Nair]

I wouldn't think its an issue with Switch. You should check with Server team why it is sending same mac over two nics..something is wrong with its config.

PS : please always rate useful posts.

HTH

Thanks,

Madhu.

[Harutyun Hakobyan]

Dear Madhu,

In Server two phisical ethernet links teamed to one virtual interface and Server sends traffic with MAC address of that Team virtual interface. That's OK.

Flapping MAC address is MAC of SW3, which is L3 switch.