2011/11/8 Zhidong <zhidong.she@gmail.com>:
> Can you guys explain why it is 10.17.64.0/20? Thanks!
11111111 = 255 in binary
11110000 = 240 in binary
So a CIDR mask of 8 would cover the first 8 bits, 16 the next 8, but
when we reach 20 we've covered 20 bits.
The first 255 is the first 8 bits. The next 255 is bits 9-16. Bits
17-20 brings it up to 240. The rest are zeros.
0.0.0.0 = /0
255.0.0.0 = /8
255.255.0.0 = /16
255.255.255.0 = /24
255.255.255.255 = /32
And inbetween you get:
255.255.240.0 = /20
255 255 240 0
11111111 11111111 11110000 00000000
First 20 binary digits are masked.
--
Thom Brown
Twitter: @darkixion
IRC (freenode): dark_ixion
Registered Linux user: #516935
EnterpriseDB UK: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
