IP ADDRESS

IP address classes

Class	1st Octet Decimal Range	1st Octet High Order Bits	Network/Host ID (N=Network, H=Host)	Default Subnet Mask	Number of Networks	Hosts per Network (Usable Addresses)
A	1 – 126*	0	N.H.H.H	255.0.0.0	126 (27 – 2)	16,777,214 (224 – 2)
B	128 – 191	10	N.N.H.H	255.255.0.0	16,382 (214 – 2)	65,534 (216 – 2)
C	192 – 223	110	N.N.N.H	255.255.255.0	2,097,150 (221 – 2)	254 (28 – 2)
D	224 – 239	1110	Reserved for Multicasting
E	240 – 254	1111	Experimental; used for research

Note: Class A addresses 127.0.0.0 to 127.255.255.255 cannot be used and is reserved for loopback and diagnostic functions.

Private IP Addresses

Class	Private Networks	Subnet Mask	Address Range
A	10.0.0.0	255.0.0.0	10.0.0.0 - 10.255.255.255
B	172.16.0.0 - 172.31.0.0	255.240.0.0	172.16.0.0 - 172.31.255.255
C	192.168.0.0	255.255.0.0	192.168.0.0 - 192.168.255.255

Subnet Masks

Prefix Format	Decimal	Available Host Addresses
/8	255.0.0.0	16777214
/9	255.128.0.0	8388606
/10	255.192.0.0	4194302
/11	255.224.0.0	2097150
/12	255.240.0.0	1048574
/13	255.248.0.0	524286
/14	255.252.0.0	262142
/15	255.254.0.0	131070
/16	255.255.0.0	65534
/17	255.255.128.0	32766
/18	255.255.192.0	16382
/19	255.255.224.0	8190
/20	255.255.240.0	4094
/21	255.255.248.0	2046
/22	255.255.252.0	1022
/23	255.255.254.0	510
/24	255.255.255.0	254
/25	255.255.255.128	126
/26	255.255.255.192	62
/27	255.255.255.224	30
/28	255.255.255.240	14
/29	255.255.255.248	6
/30	255.255.255.252	2