Nmap online course

Host discovery

Ping sweeps and when ICMP is the wrong question.

Before you scan ports, ask which addresses answer. Nmap’s default discovery mix (ICMP, TCP 80/443, and more depending on privilege) is a starting point, not a promise.

nmap -sn 172.16.10.0/24

On networks that drop ping, a host can be alive and invisible to -sn. If you already know the box exists, skip discovery with -Pn and go to ports — only on targets you are allowed to test.