nmap -sn -PR 192.168.18.110
other nmap scans to discover host.
sudo nmap -sn -PU 192.168.18.110 //UDP ping scan
nmap -sn -PE 192.168.18.110 //ICMP ping scan. Normal ping scan
nmap -sn -PE 192.168.18.1-255 //check live hosts on network range
nmap -sn -PM 192.168.18.1-255 //Mask Ping scan (use if ICMP is blocked)
nmap -sn -PP 192.168.18.1-255 //ICMP timestamp scan
nmap -sn -PS 192.168.18.1-255 //tcp syn ping scan
nmap -sn -PO 192.168.18.1-255 //IP protocol scan.use different protocols to test the connectivity