Systems and methods for synchronizing an EMACVLAN FDB among cluster units of an HA cluster are provided. According to one embodiment, real-time synchronization of a first FDB maintained within a kernel space of a first network security operating system running on a primary unit and a second FDB maintained within a kernel space of a second network security operating system running on a secondary unit is performed by: transferring information regarding an entry from the kernel space of the first network security operating system to a first synchronization unit running within a user space of the first network security operating system, and causing the second forwarding database to be updated by the first synchronization unit in response to receipt of the information regarding the entry, by transmitting the information regarding the entry to a second synchronization unit running within the user space of the second network security operating system.