VLAN Flapping in 3750x

[jaydenle]

Hi Everyone,

I recently upgraded my network to have two 3750x core, one interface on the cisco is connecting to a Netgear switch via a fiber converter. I am keep getting the vlan flapping error message in my log as below.

003396: Sep 17 01:46:16.328: %SW_MATM-4-MACFLAP_NOTIF: Host 5c0e.8ba7.0a5c in vlan 2 is flapping between port Gi2/0/15 and port Gi2/0/13

003397: Sep 17 01:46:19.843: %SW_MATM-4-MACFLAP_NOTIF: Host 5c0e.8ba7.0a5c in vlan 2 is flapping between port Gi2/0/15 and port Gi2/0/13

003400: Sep 17 01:49:58.769: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet2/0/17, changed state to down

003401: Sep 17 01:49:59.658: %LINK-3-UPDOWN: Interface GigabitEthernet2/0/17, changed state to down

003402: Sep 17 01:53:50.311: %LINK-3-UPDOWN: Interface GigabitEthernet2/0/17, changed state to up

003403: Sep 17 01:53:51.318: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet2/0/17, changed state to up

003404: Sep 17 01:57:53.262: %SW_MATM-4-MACFLAP_NOTIF: Host 5c0e.8ba7.094c in vlan 2 is flapping between port Gi2/0/15 and port Gi2/0/13

003405: Sep 17 02:05:05.435: %EC-5-CANNOT_BUNDLE2: Gi2/0/17 is not compatible with Po2 and will be suspended (flow control receive of Gi2/0/17 is on, Po2 is off)

003406: Sep 17 02:05:06.433: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet2/0/17, changed state to down

003408: Sep 17 02:07:23.470: %SW_MATM-4-MACFLAP_NOTIF: Host 000b.6cc8.39cd in vlan 2 is flapping between port Gi1/0/15 and port Gi2/0/15

003409: Sep 17 02:14:15.845: %SW_MATM-4-MACFLAP_NOTIF: Host 0023.68c9.a40c in vlan 2 is flapping between port Gi2/0/15 and port Gi1/0/15

003410: Sep 17 02:18:30.607: %SW_MATM-4-MACFLAP_NOTIF: Host 000b.6cc9.99a3 in vlan 2 is flapping between port Gi1/0/13 and port Gi2/0/15

003411: Sep 17 02:21:45.265: %SW_MATM-4-MACFLAP_NOTIF: Host 000b.6cc9.5282 in vlan 2 is flapping between port Gi2/0/15 and port Gi1/0/13

After my research i think this is a looping issue but i'm unsure how to address it. Can anyone please point me into the right direction. Many thanks your help.

[m.kafka]

this looks like a misconfigured or incorrectly patched etherchannel.

a mac address flapping between two interfaces could mean, that a port channel is avtive on the other side, unconditionally and without negotiation.

look carefully through your config, compare the patching and verify settings/configuration on your netgear (why would you connect a netgear to an enterprise grade distribution switch?)

try to disconnect either gi1/0/13 or gi1/0/15 if you can't find out about the configuration/settings of the netgear.

find out, whats about gi1/0/17, maybe that's connected to your issue.

rgds,

MiKa

[jaydenle]

Thanks for your reply Mika,

Our company was running on a mix network ie we do not have a unified network platfrom. My focus at the moment is slowly upgrading this network to use cisco but because we have a budget so we cannot replace everything at once hence have netgear connecting to cisco etc. do you think this is a sign of looping in my network? If so what can i do to prevent this? FYI, i do have RSTP enable as well as loopguard.

I will look into the netgear to see if anything is unusual about port channel setting.