NMAP - Fast Discovery

nmap -sP -T5 --min-parallelism 100 --max-parallelism 256 172.16.0.0/16 -oG - | awk '/Up$/{print $2 $3}' | nl

T5: From 1-5, 5 = insane and 3 = normal speed
-oG-: Greppable output
awk: IP and reverse name of Up devices