Nmap Host Discovery

When we try to gain access to a network, it’s important to find the list of devices connected to the network. We have to make sure the system we are trying to scan is up and running. This is where we use host discovery techniques.

Subnets

Let’s assume we have a home network that is Wi-Fi enabled. We would connect all our devices (mobile phone, PC, smart TV, etc.) to that Wi-Fi access point. When an IP address is assigned to us by our internet service provider (ISP), it’s for our entire network and not an individual device. For example, if our IP address is 17.172.333.20, this applies to our entire network.

But every device connected to the internet should always have an IP address. So, where do we get these extra IP addresses? That’s the job of the router. Each device in our network will have its own sub-IP address in a different range than that of our network.

So, assuming our IP address is 17.172.333.20, every device in our network will have an IP address starting with the format 10.x.x.x or 192.168.x.x. If the range assigned by our router is 192.168.0.x, the router will have the IP 192.168.0.1 followed by the other devices.

Here’s an example of a home network: