[Scr47h3]

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

[JaG]

whenever you get an ip address followed by a slash and a number. the number is the subnet mask.

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...bnetchart.shtml
http://www.ralphb.net/IPSubnet/
http://www.learntosubnet.com/


Hopefully i didnt make any mistakes....enjoy

[Pro21]

/24 like say Jag is the netmask notation :)
It s a CIDR notation :P

[Tuned]

you also can take a look at the ciscosite.

[The Doom Master]

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]

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!