I didn't get what ports does Nmap scan. Does Nmap start from zero or one when scan subnet or all the ports?
- 0/24 is it 0-255 or is it 1-255
- -p is it 0-65535 or is it 1-65535
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Connecting to port 0 is not possible, see
https://unix.stackexchange.com/a/180500/85039
It is a special port allowing programs to obtain random port for outgoing connection, and should not be used for incoming connections
Therefore, use -p 1-65535 for nmap, especially if you are using TCP or UDP scans
As for /24 notation that is entirely different thing: it is called CIDR notation and used to match range of hosts on network. For instance, 192.168.0.0/24 will specify all addresses between 192.168.0.0 to 192.168.0.255
answered Jan 2 '20 at 10:58
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@VenVen You can use
-p 0-65535. But trying to scan port 0 is pointless - it's never open to outside world, only to programs on the host itself. – Sergiy Kolodyazhnyy Jan 3 '20 at 6:48 -
As for
/24, yes, address range starts at 0 and goes to 255. That's 256 hosts in total theoretically. But remember that in practice 192.168.0.255 is broadcast address for the whole 192.168.0.0/24 network. Typically it's not used for a host andpingutility for example will throw an error, but it is perfectly valid address. On a different subnet other than/24, it could be a perfectly valid host. See also stackoverflow.com/a/14915309/3701431 and unix.stackexchange.com/a/407395/85039 – Sergiy Kolodyazhnyy Jan 3 '20 at 6:48
Nmap can scan all TCP UDP ports. You must to know subnetting and network knowledge. 0 port is not a standart port. For subnet if you use 24 subnetmask you will not scan 192.168.0.0 address because 24 subnetmask have a useable range for hosts. 0.0 is out of subnet useable scope. You can learn from here: http://www.steves-internet-guide.com/subnetting-subnet-masks-explained/
