CIDR notation

Here is just a CIDR(Classless Inter-Domain Routing) table for my reference on practicing GCP VPC.

CIDR prefix length	Dotted Decimal Netmask	Number of Classful Networks	Number of Usable IPs	Note
/1	128.0.0.0	128 As	2147483646	2^(32-1)-2
/2	192.0.0.0	64 As	1073741822	2^(32-2)-2
/3	224.0.0.0	32 As	536870910	2^(32-3)-2
/4	240.0.0.0	16 As	268435454	2^(32-4)-2
/5	248.0.0.0	8 As	134217726	2^(32-5)-2
/6	252.0.0.0	4 As	67108862	2^(32-6)-2
/7	254.0.0.0	2 As	33554430	2^(32-7)-2
/8	255.0.0.0	1 A or 256 Bs	16777214	2^(32-8)-2
/9	255.128.0.0	128 Bs	8388606	2^(32-9)-2
/10	255.192.0.0	64 Bs	4194302	2^(32-10)-2
/11	255.224.0.0	32 Bs	2097150	2^(32-11)-2
/12	255.240.0.0	16 Bs	1048574	2^(32-12)-2
/13	255.248.0.0	8 Bs	524286	2^(32-13)-2
/14	255.252.0.0	4 Bs	262142	2^(32-14)-2
/15	255.254.0.0	2 Bs	131070	2^(32-15)-2
/16	255.255.0.0	1 B or 256 Cs	65534	2^(32-16)-2
/17	255.255.128.0	128 Cs	32766	2^(32-17)-2
/18	255.255.192.0	64 Cs	16382	2^(32-18)-2
/19	255.255.224.0	32 Cs	8190	2^(32-19)-2
/20	255.255.240.0	16 Cs	4094	2^(32-20)-2
/21	255.255.248.0	8 Cs	2046	2^(32-21)-2
/22	255.255.252.0	4 Cs	1022	2^(32-22)-2
/23	255.255.254.0	2 Cs	510	2^(32-23)-2
/24	255.255.255.0	1 C	254	2^(32-24)-2
/25	255.255.255.128	1/2 C	126	2^(32-25)-2
/26	255.255.255.192	1/4 C	62	2^(32-26)-2
/27	255.255.255.224	1/8 C	30	2^(32-27)-2
/28	255.255.255.240	1/16 C	14	2^(32-28)-2
/29	255.255.255.248	1/32 C	6	2^(32-29)-2
/30	255.255.255.252	1/64 C	2	2^(32-30)-2
/31	255.255.255.254	1/128 C	0	2^(32-31)-2
/32	255.255.255.255	1/256 C	1	reserved

There are some range of IPv4 address reserved for special uses. More updates coming…

Published: March 20 2022