Nmap.org
Dorothy Parrott
Sometimes you wish to scan a whole network of adjacent hosts. Forthis, Nmap supports CIDR-style addressing. You can append/ to an IPaddress or hostname and Nmap will scan every IP address for which thefirst are the same as for thereference IP or hostname given. For example,192.168.10.0/24 would scan the 256 hostsbetween 192.168.10.0(binary: 11000000 10101000 00001010 00000000)and 192.168.10.255(binary: 11000000 10101000 00001010 11111111),inclusive.192.168.10.40/24 would scan exactly the same targets. Giventhat the hostscanme.nmap.orgis at the IP address 64.13.134.52, the specificationscanme.nmap.org/16 would scan the 65,536 IP addressesbetween 64.13.0.0 and 64.13.255.255. The smallest allowed value is/0, which targets the whole Internet. The largestvalue for IPv4 is /32, which scans just the named host or IPaddress because all address bits are fixed. The largest value for IPv6 is/128, which does the same thing.
Nmap accepts multiple host specifications on the command line,and they don't need to be the same type. The command nmapscanme.nmap.org 192.168.0.0/8 10.0.0,1,3-7.- does whatyou would expect.
As a starter you should check the scanme.nmap.org provided by Nmap. Then download the Metasploitable Virtual Machine provided by Offensive Security. With the Metasploitable VM you'll also practise your exploitation techniques. After these, i'd suggest you to sign up to several penetration testing online labs such us Hack The Box, TryHackMe and RootMe. When you are familiar with Nmap and other network scanning and packet capturing tools (Wireshark very useful), you could setup your own virtual or physical Lab for more Advanced - Field Testing.
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