«

[super1435]

I have three stacked C3750G-12 switches running as a core. There is a pair of FW's connected to this stack on gig2/0/11 and 3/0/11. Theses ports are on a VLAN 991 that has 130.151.254.120 /29 subnet assigned. The switch is getting the following error ....

Jul 10 11:56:49.080 CDT: %SW_MATM-4-MACFLAP_NOTIF: Host 0000.0000.fe21 in vlan 991 is flapping between port Gi2/0/11 and port Gi3/0/11

The FW group does not see any MAC Flap errors on their FW interfaces. How can I correct this problem? I just upgraded to the 122-44 code two days ago with no success in eliminating this issue.

Flap is occurring between 2/0/11 & 3/0/11At this time, we have not setup anything other than plugging the two firewalls into separate ports.

[kadar]

We were facing the same problem. The answer we got from the company which is supporting us is:
"Because both appliances are configured as “part of a cluster” but none of them has yet taken the role of the primary, this MAC is broadcasted by both appliances"

So if you eventually configure your appliances to work in cluster mode, the issue should be resolved.

HTH

[kadar]

Surely you have resolved the issue, since your post has been up since 2008, but maybe this answer can benefit someone else.