TCP/IP Subnet Table

Prefix	Subnet Mask	Number of Hosts	Networks (Class B) *	Networks (Class C) *	Inverse Mask +	Notes
/16	255.255.0.0	65534	1		0.0.255.255	Class B
/17	255.255.128.0	32766	0+1		0.0.127.255	In Class A networks, CIDR, or subnet-zero enabled networks only
/18	255.255.192.0	16382	2+1		0.0.63.255
/19	255.255.224.0	8190	6+1		0.0.31.255
/20	255.255.240.0	4090	14+1		0.0.15.255
/21	255.255.248.0	2046	30+1		0.0.7.255
/22	255.255.252.0	1022	62+1		0.0.3.255
/23	255.255.254.0	510	126+1		0.0.1.255
/24	255.255.255.0	254	254+1	1	0.0.0.255	Class C
/25	255.255.255.128	126	510+1	0+1	0.0.0.127	in class B or larger networks, CIDR, or subnet-zero enabled networks only
/26	255.255.255.192	62	1022+1	2+1	0.0.0.63
/27	255.255.255.224	30	2046+1	6+1	0.0.0.31
/28	255.255.255.240	14	4090+1	14+1	0.0.0.15
/29	255.255.255.248	6	8190+1	30+1	0.0.0.7
/30	255.255.255.252	2	16382+1	62+1	0.0.0.3
/31	255.255.255.254	0				Invalid mask since it leaves no host bits
/32	255.255.255.255	1			0.0.0.0	Special single host mask

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