Track hosts that are up
Vlinux6 gave you the answer. You can make it a cron job if you want that's easy, not much to know about cron.
type "nmap -v -A <ip address range>/24
i.e nmap -v -A 192.168.0.254/24
You will get plenty of interesting information.
If Vlinux6 answer confused you go learn some bash,