How to See All Devices on Your Network With nmap on Linux
nmap is a network mapping tool. It works by sending various network messages to the IP addresses in the range we’re going to provide it with it. It can deduce a lot about the device it is probing by judging and interpreting the type of responses it gets.
Let’s kick off a simple scan with nmap. We’re going to use the -sn (scan no port) option. This tells nmap to not probe the ports on the devices for now. It will do a lightweight, quick scan.
Even so, it can take a little time for nmap to run. Of course, the more devices you have on the network, the longer it will take. It does all of its probing and reconnaissance work first and then presents its findings once the first phase is complete. Don’t be surprised when nothing visible happens for a minute or so.
The IP address we’re going to use is the one we obtained using the ip command earlier, but the final number is set to zero. That is the first possible IPAddress on this network. The «/24» tells nmap to scan the entire range of this network. The parameter «192.168.4.0/24» translates as «start at IP address 192.168.4.0 and work right through all IP addresses up to and including 192.168.4.255».
Note we are using sudo.
sudo nmap -sn 192.168.4.0/24