Network › network, the scan bar above the device table. The tick saves immediately. Scan now still needs the machine online.
Open the machine, then network › network. The bar under the address tiles is the scan. Weekly scan is clear, and the note says off. Spare laptop has no snapshot yet. Scan now is there because the machine is online; leave it. The weekly tick is the schedule, and it saves on its own. Read devices found on the LAN is the table a scan fills.
Tick weekly scan. It saves on its own: Sundays at 02:00 Australia/Melbourne, on this machine's subnet. Active probe stays a choice for a scan you start by hand. A host that misses two scheduled passes is marked gone. Clear the tick to stop the weekly pass. The next online heartbeat is when a scan can actually run.
Accounts server already has this on, Sundays at 02:00, for 10.1.1.0/24. Pinging each address on the next scan is Probe the LAN instead of only listening. Reading the rows is Read devices found on the LAN. The address tiles above the bar are See how a machine is connected.