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. |