Host discovery

A network comprises many hosts based on the subnet provided. For example, a subnet with a mask value of 27 will have 32 hosts, whereas a subnet with a mask value of 24 will have 256 hosts. A full port scan on 256 hosts, without knowing which of those hosts are live, could take a lifetime. In order to reduce the traffic generated and processed by Nmap we can filter the network hosts based on live and non-live hosts. This will allow Nmap to reduce unwanted analysis and obtain results quicker.