nmap

to probe a single target, specify the host name or address

nmap -v target.example.com
nmap -v 10.12.104.200
nmap -v 122.166.23.91,20-25

by default , nmap uses both TCP and ICMP pings for host discovery. if these are blocked by an intervening firewall, the nmap -P options provide alternate ping strategies. if you know that your targets are up , you can disable host discovery with the -P0 option.


run nmap as root if possible. some of its more advanced tests intentionally violate IP protocols., and require raw sockets that only the super user is allowed to access.

use -F option to quickly scan only the well known ports, or the -p option to select different, specific, numeric range of ports. if you want to exhaustively scan all ports, use -p 0 - 65535
disable port scanning entirely with nmap -sP option.

nmap -O enables the operating system fingerprinting.