The purpose of this post is to introduce a user to the nmap command line tool to scan a host and/or network, so to find out the possible vulnerable points in the hosts. You will also learn how to use Nmap for offensive and defensive purposes.

via Top 30 Nmap Command Examples For Sys/Network Admins.

Nmap can be very useful which is why I have a link to it in the Tools section on this page.