Nmap (“Network Mapper”) is another great tool for network monitoring and security auditing.
It is a free and open source multi-platform utility designed to scan networks for host discovery, port scanning (opened port number as well as associated service, amount of closed ports ), distance to host, Mac Adresses, host OS detection, etc.
Using a terminal
To check whether you have it installed in your shell
nmap –version
If you do not have it you will have to use the command line to install it. On a distribution with package manager, it is going to be:
sudo pacman -S nmap
Some examples of commands
There are far more options available in the reference guide of Nmap. -O requires elevated privileges and is necessary for OS detection and manufacturer’s Mac address identification.-sP can be used to skip port scan in the results.
Scanning one IP address
nmap -O 192.168.1.10
Scanning the IP range from 1 to 10 in the subnet
nmap -O 192.168.1.1-10
Scanning an entire subnet = the whole range from 0 to 255
nmap -O 192.168.1.0/24
Scanning an entire subnet but exclude hosts from 120 to 140
nmap -O 192.168.1.0/24 –exclude 192.168.1.120-140
The last device to appear in the list is the scanning machine (if not excluded).
Nmap is installed by default in Mac OS and some Linux distributions as a command line tool. However a GUI version called (zenmap) is also available for other Oses.