Problem on Cat3560-E

[dennisopiso]

our network went down, upon checking got this error message from the switch:

%SW_MATM-4-MACFLAP_NOTIF: Host 0024.0000.0000 in vlan xx is flapping between port Po1 and port Gi0/1

found a recommendation from cisco saying "check configuration of data forwarding loop". checked and double checked the config and i found nothing suspicious.

help please

[andrew.prince]

I have seen something like this before - on a server that had 2 nics, that were dual homed.

The NIC's were fighting to become the master NIC.

HTH>

[glen.grant]

you can also this when someone has bridged 2 ports together on the swith and that will bring it to its knees.

[dennisopiso]

here is what my network looks like

core switch

|

|

|

distribution switch (3560E)

|

|

|-- access switch1

|-- access switch2

|-- access switch3

3560e is connected to the core via etherchannel

[Leo Laohoo]

Mabuhay kabayan.

You'll need to trace down the physical port of both macs, disconnect it and observe if the MAC flapping still occurs. If it has stopped then disable the bridging of the server before connecting the 2nd NIC back.

I am curious how this MAC flapping can cause a network outage. I've seen my fair share of this type of logs but never to a point that it could bring your network to it's knees ... unless you had an STP loop.

Hope this helps.