[230517]BIT별 서브넷정리-네트워크 서브넷을 구성할 때 필수

bit	netmask	Cisco mask	hosts	usable hosts	Class
/ 4	240.0.0.0	15.255.255.255	268435456	268435454 -
/ 5	248.0.0.0	7.255.255.255	134217728	134217726 -
/ 6	252.0.0.0	3.255.255.255	67108864	67108862 -
/ 7	254.0.0.0	1.255.255.255	33554432	33554430 -
/ 8	255.0.0.0	0.255.255.255	16777216	16777214	A Class
/ 9	255.128.0.0	0.127.255.255	8388608	8388606	-
/ 10	255.192.0.0	0.63.255.255	4194304	4194302	-
/ 11	255.224.0.0	0.31.255.255	2097152	2097150	-
/ 12	255.240.0.0	0.15.255.255	1048576	1048574	-
/ 13	255.248.0.0	0.7.255.255	524288	524286	-
/ 14	255.252.0.0	0.3.255.255	262144	262142	-
/ 15	255.254.0.0	0.1.255.255	131072	131070	-
/ 16	255.255.0.0	0.0.255.255	65536	65534	B Class
/ 17	255.255.128.0	0.0.127.255	32768	32766	-
/ 18	255.255.192.0	0.0.63.255	16384	16382	-
/ 19	255.255.224.0	0.0.31.255	8192	8190	-
/ 20	255.255.240.0	0.0.15.255	4096	4094	-
/ 21	255.255.248.0	0.0.7.255	2048	2046	-
/ 22	255.255.252.0	0.0.3.255	1024	1022	-
/ 23	255.255.254.0	0.0.1.255	512	510	-
/ 24	255.255.255.0	0.0.0.255	256	254	C Class
/ 25	255.255.255.128	0.0.0.127	128	126	-
/ 26	255.255.255.192	0.0.0.63	64	62	-
/ 27	255.255.255.224	0.0.0.31	32	30	-
/ 28	255.255.255.240	0.0.0.15	16	14	-
/ 29	255.255.255.248	0.0.0.7	8	6	-
/ 30	255.255.255.252	0.0.0.3	4	2	-
/ 31		point to point links only
/ 32	255.255.255.255	use host notaition	1	1	-

참고 :
https://jjaekjjaek.tistory.com/entry/Subnet-mask%EC%84%9C%EB%B8%8C%EB%84%B7-%EB%A7%88%EC%8A%A4%ED%81%AC-%EB%B9%84%ED%8A%B8-%EB%B3%84-%EC%A0%95%EB%A6%AC