Very simple subnet question

lukameen · 11-02-2005, 01:24 PM

Okay, this is a dummy type question. When the address range of an IP scope for a subnet is denoted as (for example) 154.83.65.128/25, what does the /25 represent?

stickman · 11-02-2005, 01:33 PM

/25 is equivalent to 255.255.255.128.

lukameen · 11-02-2005, 01:40 PM

Thanks. Could you explain how to translate the /25 to that subnet mask?

michaelk · 11-02-2005, 01:49 PM

/25 is the netmask

/ 25 means:
In binary:
11111111.11111111.11111111.10000000
11111111 b = 255 d
10000000 b = 128 d
therefore 255.255.255.128

Another example
/8 means
255.0.0.0
11111111.00000000.00000000.00000000

lukameen · 11-02-2005, 01:55 PM

Thank-you.

bullium · 11-02-2005, 02:40 PM

Complete list

if you notice there is a pattern.

255.0.0.0 = /8
255.128.0.0 = /9
255.192.0.0 = /10
255.224.0.0 = /11
255.240.0.0 = /12
255.248.0.0 = /13
255.252.0.0 = /14
255.254.0.0 = /15
255.255.0.0 = /16
255.255.128.0 = /17
255.255.192.0 = /18
255.255.224.0 = /19
255.255.240.0 = /20
255.255.248.0 = /21
255.255.252.0 = /22
255.255.254.0 = /23
255.255.255.0 = /24
255.255.255.128 = /25
255.255.255.192 = /26
255.255.255.224 = /27
255.255.255.240 = /28
255.255.255.248 = /29
255.255.255.252 = /30