GratuitousARPAmbiguousTerminology

The difference between ARPAnnouncement and GratuitousARPRequest is one of context (the packets are identical), with ARPAnnouncement being a specific use case of GratuitousARPRequest @ref

The term “ARP Announcement” comes from RFC5227 (IPv4 Address Conflict Detection) which is about ARPDuplicateAddressDetection. @ref

RFC5227 introduced the new name partly because GratuitousARP had become ambiguous, since people used it for both requests and replies. @ref

The real difference is that ARPAnnouncement refers to a specific step in a defined procedure, ARPDuplicateAddressDetection @ref

GratuitousARPRequest is the older, more generic term. It describes the packet itself, sent for any reason at any time, such as a failover, a MAC change, or a periodic refresh. It doesn’t imply that any probing happened first. @ref

So every ARP Announcement is a gratuitous request, but calling something an “announcement” usually signals it’s being sent as part of RFC 5227 conflict detection. @ref