What are IP address blocks or IP ranges? -


sometimes web developers use ip address blocks or range handle traffic coming ip range (ip block), ip range used when want block robots accessing websites & lots more uses.

i unable understand 1 thing, seeing info ips here http://ipinfo.io/as16509 , read "103.246.150.0/23 has 512 ip addresses",

ok "/23" means in "103.246.150.0/23" ? in past whenever read "103.246.150.0/23" thought means 23 ip addresses 103.246.150.0, 103.246.150.1, 103.246.150.2....... 103.246.150.23 . not true, contains 512 ips, read here http://ipinfo.io/as16509 ,

then "/23" means?

and facebook provide range of ips handle bots, example

31.13.24.0/21

66.220.144.0/20

so above ips , how many ips?

see classless inter-domain routing (cidr) notation.

the number after slash / indicates how many bits form subnet mask. /23 contains 512 addresses because subnet specified in first 23 bits , remaining 32 - 23 = 9 bits give 29 = 512 addresses in subnet. (ipv4 addresses 4 bytes, or 32 bits.)

for more detailed answer, see same question on network engineering stack exchange.


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