This object holds the port (ifIndex) that a logged MAC address moved away from on the VLAN in zxAnMasMacMoveLogVid, populated only when zxAnMasEnable and zxAnMasMacMoveReportEnable are both enabled and a move was detected. Admins use it, alongside the destination port, to trace exactly where a MAC address relocated from, helping distinguish a legitimate reconnection from a spoofing attempt. For example, an admin investigating an alert would check whether this source port matches where the legitimate device was last known to be connected.