What is the purpose of MAC masquerading.

MAC masquerading does not prevent ARP cache errors; it reduces the time routers need to learn the new MAC after failover, which is a latency and availability concern rather than an error prevention mechanism.

MAC masquerading does not reduce the number of ARP table entries on routers; it ensures the floating MAC is quickly reassociated with the correct device, not that fewer entries are created.

Without MAC masquerading, a failover causes the newly active device to present a different hardware MAC address, requiring all upstream routers to refresh their ARP caches before traffic can flow - this delay drops connections. MAC masquerading provides a consistent floating MAC that moves with the active role, so after the new active device sends a gratuitous ARP, traffic resumes with minimal interruption.

Both BIG-IP devices do not simultaneously use the same MAC address; only the currently active device uses the masquerade MAC, and it transfers exclusively to the new active device upon failover.