NDP Status

The RFC 4861 defines a number of statuses:

Status	Description	Comment
INCOMPLETE	Address resolution is in progress and the link-layer address of the device has not yet been determined.
REACHABLE	Device is known to have been reachable recently (within tens of seconds ago).
STALE	Device is no longer known to be reachable but until traffic is sent to the neighbor, no attempt should be made to verify its reachability.
DELAY	Device is no longer known to be reachable, and traffic has recently been sent to the neighbor. Probes should be delayed in order to give upper-layer protocols a chance to provide reachability confirmation.
PROBE	Device is no longer known to be reachable, and unicast Neighbor Solicitation probes are being sent to verify reachability.