Nmap scans are divided in several phases. Some of them require some arguments to be set to run, but others, such as the reverse DNS resolution, are executed by default. Let's review the phases that can be skipped and their corresponding Nmap flag:
- Target enumeration: In this phase, Nmap parses the target list. This phase can't exactly be skipped, but you can save DNS forward lookups using only the IP addresses as targets.
- Host discovery: This is the phase where Nmap establishes if the targets are online and in the network. By default, Nmap sends an ICMP echo request and some additional probes, but it supports several host discovery techniques that can even be combined. To skip the host discovery phase (no ping), use the flag ...
