NMAP, short for Network Mapper, is a powerful open-source tool primarily used for security auditing and network exploration. Using NMAP, you can not only identify active IP addresses on a network but also discover open ports, running services, OS versions, and much more within those active hosts.
To use NMAP to find active IP addresses in a network, you first need to install the tool. NMAP can be downloaded and installed on various platforms following the instructions from the official website (https://nmap.org/download.html) or via package managers like apt, yum, or homebrew, depending on your operating system.
The simplest command to scan a single IP address is “nmap [IP Address]”. For example, “nmap 192.168.1.1” would scan that specific IP address.
A range of IPs can also be scanned by specifying the range. For example, “nmap 192.168.1.1-10” would scan IP addresses from 192.168.1.1 through 192.168.1.10. You can also use the wild card “” to scan an entire subnet. For instance “nmap 192.168.1.” would scan all 254 potential IP addresses in that subnet.
To find active IP’s, you’ll generally use the “-sn” parameter, or alternatively, the “-sP” parameter for older versions of NMAP. This command initiates what’s called a “ping scan”. The full command would be “nmap -sn [IP Range]”. This will provide a list of “hosts up”.
Following is a sample command and output:
```
$ nmap -sn 192.168.1.0/24
Starting Nmap at some-time
Nmap scan report for 192.168.1.1
Host is up (0.013s latency).
Nmap scan report for 192.168.1.2
Host is up (0.013s latency).
Nmap done: 256 IP addresses (2 hosts up) scanned in 3.29 seconds
```
The command “nmap -sn 192.168.1.0/24” initiates a ping scan for the subnet 192.168.1.0/24 and the output provides a list of active IP addresses.
NMAP may not work properly for larger IPs as some network administrators block ping requests to counteract scanning. Therefore, when using the tool for scanning larger IPs or over the internet, please exercise caution and respect as unauthorized scanning may violate laws and result in being banned from networks.
The official documentation can be accessed for further information regarding the NMAP (https://nmap.org/book/man.html). Note that you should have permission to scan any network and always respect privacy and legal guidelines.
Referenced Sources:
1. NMAP Download – https://nmap.org/download.html
2. NMAP Manual – https://nmap.org/book/man.html
