How to scan multiple networks with NMAP?

Nmap, which stands for Network Mapper, is a popular and powerful open source tool used by network administrators, system administrators, and cybersecurity professionals for network discovery, auditing, and security scanning. Developed by Gordon Lyon, also known as Fyodor, this tool is widely used to identify available hosts, the services these hosts provide, their operating systems, packet filters/firewalls, and many other features. Source: (Nmap.org, n.d.)

Scanning multiple networks with Nmap is relatively straightforward. Here’s a general technical guide on how to do that.

First, you should install Nmap on your system. Nmap can be installed on multiple operating systems, including Windows, Mac OS X, and Linux distributions. After the installation, you should open the command line interface (CLI)—such as Bash, PowerShell or Terminal—depending on your operating system. Source: (Harris, 2012)

To scan multiple networks, you need to set their IP ranges in your command. Here’s an example:

nmap 192.168.1.1-255 192.168.2.1-255

This command will scan all the hosts in two different networks: 192.168.1.0/24 and 192.168.2.0/24.

Alternatively, you can scan multiple networks using a different netmask, for instance:

nmap 192.168.1-2.0-255

This command will scan all hosts in the range from 192.168.1.0 all the way to 192.168.2.255. Source: (Lyon, 2009)

Bear in mind that Nmap without any command switch will only perform a ping sweep, which will tell you which hosts are online. If you want to know more about these hosts, like their open ports or operating systems, you can add command switches like:

-sS for SYN scan -sU for UDP scan -p for specific port range -O for OS detection

Always remember that scanning a network that you do not own or do not have permission to scan is illegal. Always obtain proper authorization before conducting a network scan.

In conclusion, Nmap is a highly versatile tool used for network mapping and auditing. Scanning of multiple networks can be achieved by defining the IP ranges in the CLI. Although the application is powerful, users should always remember to obtain required permissions to avoid illegal activities.

References: 1. Nmap.org. (n.d.). Nmap: the Network Mapper – Free Security Scanner. https://nmap.org/ 2. Harris, O. (2012). Nmap in the Enterprise: Your Guide to Network Scanning. Syngress. 3. Lyon, G. (2009). Nmap Network Scanning: The Official Nmap Project Guide to Network Discovery and Security Scanning. Nmap.