I've seen this trap a few times, and it can mean a lot of things depending on the service being provided over the vlan. In my experience, it can happen in large layer-2 service provider networks, where a vlan will carry a customer point-to-point link, and two links are bundled outside of your layer-2 network.
If you are providing layer-2 circuits through these vlans, it would indicate that your vlans 402 and 403 are bundled by the end user and load-sharing is performed between the two links. If spanning-tree takes these two vlans through different paths, it could confuse the CAM table, and make it see that mac address coming from two different ports thus giving you an error like this. This mostly happens in larger layer-2 service provider networks. Does this make sense to you? Allan On Thu, Oct 16, 2008 at 12:56 PM, Church, Charles <[EMAIL PROTECTED]> wrote: > Sounds like an attempt at a man in the middle attack, where an infected > host attempts to act as the gateway to see all the network traffic, > analyze it, then forward it to the real gateway. Definitely not a good > thing. > > Chuck > > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Wyatt Mattias > Gyllenvarg > Sent: Thursday, October 16, 2008 6:27 AM > To: Ozgur Guler; [email protected] > Subject: Re: [c-nsp] %SW_MATM-4-MACFLAP_NOTIF > > > Hi all > > We have seen 3 instances of this the last days where a host (probably > infected with a virus) has been broadcasting the mac of the local GW. > > Effectivly switching alla outbound traffic too his port. > > Fix has been too shutdown the offending port. > > So far this has only effected older setups. > > //Mattias Gyllenvarg > > > > 2008/10/16 Ozgur Guler <[EMAIL PROTECTED]>: >> >> "no mac address-table notification mac-move" might help. >> >> >> >> --- On Thu, 16/10/08, Jimmy Halim <[EMAIL PROTECTED]> wrote: >> From: Jimmy Halim <[EMAIL PROTECTED]> >> Subject: [c-nsp] %SW_MATM-4-MACFLAP_NOTIF >> To: [email protected] >> Date: Thursday, 16 October, 2008, 7:51 AM >> >> Hi guys, >> >> Recently I am getting the following log messages every 2 mins on the > 3750 >> switch. >> >> Oct 16 06:45:50 UTC: %SW_MATM-4-MACFLAP_NOTIF: Host 0017.cbb3.08fc in > vlan >> 403 is flapping between port Fa1/0/3 and port Gi1/0/1 >> Oct 16 06:45:50 UTC: %SW_MATM-4-MACFLAP_NOTIF: Host 0017.cbb3.08fc in > vlan >> 402 is flapping between port Fa1/0/2 and port Gi1/0/1 >> Oct 16 06:46:43 UTC: %SW_MATM-4-MACFLAP_NOTIF: Host 0017.cbb3.08fc in > vlan >> 402 is flapping between port Fa1/0/2 and port Gi1/0/1 >> >> This is non service impacting so far. However, I would like to know > whether >> we can disable this logging or not. Anyone has any suggestions? >> >> Many Thanks, >> Jimmy >> >> _______________________________________________ >> cisco-nsp mailing list [email protected] >> https://puck.nether.net/mailman/listinfo/cisco-nsp >> archive at http://puck.nether.net/pipermail/cisco-nsp/ >> >> >> >> >> _______________________________________________ >> cisco-nsp mailing list [email protected] >> https://puck.nether.net/mailman/listinfo/cisco-nsp >> archive at http://puck.nether.net/pipermail/cisco-nsp/ >> > _______________________________________________ > cisco-nsp mailing list [email protected] > https://puck.nether.net/mailman/listinfo/cisco-nsp > archive at http://puck.nether.net/pipermail/cisco-nsp/ > _______________________________________________ > cisco-nsp mailing list [email protected] > https://puck.nether.net/mailman/listinfo/cisco-nsp > archive at http://puck.nether.net/pipermail/cisco-nsp/ > _______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
