MAC Flaps in a switch network with no redundancy

[Derick Needham]

I am working on a customer site and in the current topology, there are 3 daisy chained switches.

The switches are generating MAC flaps between multiple ports resulting in very poor performance.

These events occur sporadically and eventually quiet down. The connection improves eventually until the next event:

Jun  8 07:58:22.928: %SW_MATM-4-MACFLAP_NOTIF: Host 0026.bb6c.20fd in vlan 1 is flapping between port Gi0/15 and port Gi0/25

The  current code is :

c2960l-universalk9-mz.152-5c.E/c2960l-universalk9-mz.152-5c.E.bin

Thanks

Derick

[Mark Malone]

any current stp changes happening when you see the logs , did you check the cdp to make sure they were definitely not looped somewhere

any wireless controllers or aps involved in local network

sh spanning-tree de | i ieee|is from|occurr|exec

[Derick Needham]

Hello Mark,

There are several low end access points such NetGear are connected to these switches.

No physical loops and no recent changes in STP configuration.

 I will run the suggested command above when I am at the customer site probably tomorrow.

Thanks

Derick.

[johnd2310]

HI,

What end devices do you have a connect to the switches, Wireless access points, phones?

Thanks

John

[farcosre]

Hi

-When did the problem start?
- Are you still seeing the error?
- Who owns the MAC 0026.bb6c.20fd? Is the owner (device) directly connected
to the switch?
- What devices are connected to ports Gi0/15 and Gi0/25?
- Do you have a server with 2 NIC cards or access-points associated with
these interfaces?
- How are these ports configured?
- Are you only seeing one MAC address flapping between these two ports?
- What are the recent changes done prior to encountering the issue?
- So far, what initial troubleshooting steps have you done for this device?
- Could you please send me the "show tech", "sh mac-address-table" and "show
log" of the switch?
 
Also, could you please provide:
- Network Topology.
- Specific port numbers on where the other devices are connected (if the
issue involves connectivity issues or multiple switches).
- Significant addresses (IP and MAC address).

Host [mac-addr] in vlan [dec] is flapping between port [char] and port
[char]
This message indicates that the specified host is detected as a source
address on multiple ports. Normally, a host is supposed to be learned on only one port. The most
common cause of this condition is spanning tree loops. All traffic from the specified
host is temporarily dropped. After 15 seconds, forwarding is reenabled.