2011/11/8 Zhidong <zhidong....@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 -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
