I was looking for a device on a x460 switch by mac. I ran sh fdb . The return listed the machine's mac on our gateway port. I found the correct port by using the phone's mac which showed the correct port that the device was connected. The machine had no physical connection to the gateway port !!!! Anyone have any ideas how this could happen. The device port was a netlogin configured port.
Most likely switch recieved packet on port 4:4 with SMAC *:13:d2:dd. Do you always see the issue or it happened once? What happenes when FDB entry ages out?
A topology diagram showing your network layout particular is there are any redundant links would help better answer your question. Also, do you have CDP enabled devices communicating through the switch or sending CDP packets to the switch?