11-11-2013 12:16 AM - edited 03-07-2019 04:31 PM
Recieving Mac flapping on the ports going to Building A and B. Mac address is actually the address of vlan 4 gateway virtual interface at building A. This happens for the most part everday around 1PM. It brings down the Vlan until you reset either int g0/46 or 47 on the 2960. (activity led's on all switches blink in sync). I have verified that there are no switching loops. Syslog sample is below.
2013-10-31 14:53:29 local7.warning 10.1.0.20 26968: Oct 31 14:53:28: %SW_MATM-4-MACFLAP_NOTIF: Host 6416.8db2.8742 in vlan 4 is flapping between port Gi0/1 and port Gi0/47
2013-10-31 14:54:22 local7.warning 10.1.0.20 26972: Oct 31 14:54:20: %SW_MATM-4-MACFLAP_NOTIF: Host 6416.8db2.8742 in vlan 4 is flapping between port Gi0/46 and port Gi0/1
2013-10-31 14:55:07 local7.warning 10.1.0.20 26975: Oct 31 14:55:06: %SW_MATM-4-MACFLAP_NOTIF: Host 6416.8db2.8742 in vlan 4 is flapping between port Gi0/46 and port Gi0/47
when the incident happens, from the tigerswitches perspective, they see the Mac originating from g0/1 which is what I would expect. Can anyone point me in the right direction? I am about ready to chalk it up to tigerswitches malfunctioning, but the static timeline has me hesitant. Let me know if you need further logs.
Thoughts:
MITM spoofing gateway mac address?
Malfunctioning Tigerswitches injecting learned mac address back into network (logs dont show any issues)
Thanks,
Mark.
11-11-2013 03:07 AM
This looks very strange. You don't even have a physical loop according to your diagram. Does this always happen at the same time? Are you aware of anything that happens at that time? Some automatic system running or anything?
I would look into the Tiger switches.
Daniel Dib
CCIE #37149
11-12-2013 10:52 AM
Only physical loop is the stacked 3750 core(with stacking cables) if you can call that a loop. Single ptp to the other switches. I am not aware of any processes that run at the same time. I am going to try replacing one of the SMC's and see if it alleviates the flapping from that port at least.
Thanks for your reply,
-Mark
11-12-2013 12:34 PM
Very Starnge, indeed. Are there any wireless devices at building A, B, or C? Also what IOS version is on the 3750 stacks?
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