This attribute indicates whether the local device specified by mac is
reachable or unreachable from this SNA DLR interface. The
device status is determined by the SNA DLR service by sending a
TEST frame with the Poll bit set to the device periodically. If a
TEST frame with the Final bit set is received from the device then
the device status becomes reachable; otherwise the device status is
unreachable.
When the device status is reachable, connections to this device are
accepted. When the device status is unreachable, existing
connections to the device are cleared and new connections are
cleared to hunt or redirection services.