First step in the process of penetration testing is “Information gathering”, the phase where it is useful to get as much information about the target(s) as possible. While it might be different for the different type of penetration tests, such as web application or mobile application pentest, network scanning is a crucial step in the infrastructure or network pentest.
Let’s take a simple scenario: you are a penetration tester and a company want to test one of its servers. They send you the IP address of the server. How to proceed? Although nmap allows to easily specify multiple IP targets or IP classes, to keep things simple, I will use a single target IP address which I have the permission to scan (my server): 220.127.116.11.