CIDR	サブネットマスク	IPアドレス数
/32	255.255.255.255	1
/31	255.255.255.254	2
/30	255.255.255.252	4
/29	255.255.255.248	8
/28	255.255.255.240	16
/27	255.255.255.224	32
/26	255.255.255.192	64
/25	255.255.255.128	128
/24	255.255.255.0	256
/23	255.255.254.0	512
/22	255.255.252.0	1,024
/21	255.255.248.0	2,048
/20	255.255.240.0	4,096
/19	255.255.224.0	8,192
/18	255.255.192.0	16,384
/17	255.255.128.0	32,768
/16	255.255.0.0	65,536
/15	255.254.0.0	131,072
/14	255.252.0.0	262,144
/13	255.248.0.0	524,288
/12	255.240.0.0	1,048,576
/11	255.224.0.0	2,097,152
/10	255.192.0.0	4,194,304
/9	255.128.0.0	8,388,608
/8	255.0.0.0	16,777,216
/7	254.0.0.0	33,554,432
/6	252.0.0.0	67,108,864
/5	248.0.0.0	134,217,728
/4	240.0.0.0	268,435,456
/3	224.0.0.0	536,870,912
/2	192.0.0.0	1,073,741,824
/1	128.0.0.0	2,147,483,648
/0	0.0.0.0	4,294,967,296