Scr47h3
May 8 2005, 02:46 AM
Hey all,
I'm just curious about what something means. In the help file for NMAP, I saw a thing that was an IP address followed by a slash and a number, and I don't know what it means. Is this used to refer to computers behind a router, or something? Here's an example of what it looks like (I'm using a made-up IP, here):
10.4.208.71/16
What is that refering to? I'm pretty sure it's not the same thing as "10.4.208.71-79", because that is what NMAP uses to scan a range of IP addresses. I'm pretty sure that the thing I'm curious about isn't even specific to NMAP, because I think I've seen it somewhere else? Can anyone tell me?
Thanks,
Evan
whenever you get an ip address followed by a slash and a number. the number is the subnet mask.
CODE
example:
1)
10.4.208.71/24
24 255.255.255.0 = 11111111.11111111.11111111.11111111.0
|_________________________________|
|
24
2)
10.4.208.71/16
16 = 255.255.0.0 = 11111111.11111111.0.0
|________________|
|
16
3)
10.4.208.71/15
15 = 255.254.0.0 = 11111111.11111110.0.0
|_______________|
|
15
If you want to learn more about subnetting check out:
http://www.pantz.org/networking/tcpip/subnetchart.shtmlhttp://www.ralphb.net/IPSubnet/http://www.learntosubnet.com/Hopefully i didnt make any mistakes....enjoy
Pro21
May 8 2005, 05:41 AM
/24 like say Jag is the netmask notation
It s a CIDR notation
Tuned
May 8 2005, 06:55 AM
you also can take a look at the ciscosite.
The Doom Master
May 9 2005, 02:51 PM
the /# means the subnet of the IP
for example:
/24 - 255.255.255.0 (24-1bits,8-0bits out of 32bits total)
/16 - 255.255.0.0
/8 255.0.0.0
no_stress
May 17 2005, 11:39 AM
that is a way to describe ranges!
the number after the slash is the length of a mask in bits.
each ip has 32 bits. for example:
200.23.0.0 = 11001000 00010111 00000000 00000000
the mash "holds" the 1st X bits
200.23.0.0/16 = 11001000 00010111 xxxxxxxx xxxxxxxx = 200.23.* = 200.23.0.0-200.23.255.255
200.23.1.0/24 = 11001000 00010111 00000001 xxxxxxxx = 200.23.1.* = 200.23.1.0-200.23.1.255
0.0.0.0/0 is the whole internet...
200.23.1.0/31 is just 2 IP's: 200.23.1.0 and 200.23.1.1
etc..etc...
hope you understand!
