NMAP is probably best port scanner and network exploration/security auditing tool what you can find for free. So here is some really basic things how to use it.
There is many ways to scan with nmap:
Using wildcard mask: nmap 192.168.0.* Scan’s 192.168.0.0 – 192.168.0.255
With range: nmap 192.168.0.1-100 Scan’s 192.168.0.1 – 192.168.0.100
Using notation: […]