Detecting systems on your network with NMAP

If you have heard of nmap before, it was likely as a hacker tool. These days it is most commonly used as a port scanner, but it actually started its life as a network-mapping tool for discovering hosts. In fact, nmap stands for Network Mapper. It can utilize ICMP, UDP, and TCP.

Let us look at how to utilize it to discover what systems exist on your network.

How to do it…

First, we need to make sure that we have nmap installed. Luckily, it is a common enough tool to be available in the package repository for your selected distribution, and it will be accessible either by running sudo apt-get install nmap or sudo yum install nmap.

Next, we will do a simple ICMP sweep of the network to see who responds:

# nmap -sP 10.0.0.0/24
Starting Nmap 6.40 ( http://nmap.org ) at 2016-05-03 15:43 EDT
Nmap scan report for 10.0.0.1
Host is up (0.00053s latency).
MAC Address: 52:54:00:65:7D:0A (QEMU Virtual NIC)
Nmap scan report for 10.0.0.10
Host is up.
Nmap done:...