Subnet Masks Reference Table

Subnetting is the process of dividing one network into smaller networks. Collectively, the smaller networks are referred to as subnetworks (or subnets), and the singular subdivision is a subnetwork (more commonly referred to as a subnet). Every single computer that is connected to a subnet shares an identical portion of the IP address. This shared information is known as a routing prefix, and in IPV4 (Internet Protocol Version 4), the routing prefix is called a subnet mask. The subnet mask is a "quad-dotted decimal representation".

This IPv4 Subnet Chart can assist you in looking up how a network is broken up into subnets.

Class address ranges:

• Class A = 1.0.0.0 to 126.0.0.0
• Class B = 128.0.0.0 to 191.255.0.0
• Class C = 192.0.1.0 to 223.255.255.0

Reserved address ranges for private (non-routed) use:

• 10.0.0.0 -> 10.255.255.255
• 172.16.0.0 -> 172.31.255.255
• 192.168.0.0 -> 192.168.255.255

Other reserved addresses:

• 127.0.0.0 is reserved for loopback and IPC on the local host
• 224.0.0.0 -> 239.255.255.255 is reserved for multicast addresses

Chart notes:

• Number of Subnets - "( )" Refers to the number of effective subnets, since the use of subnet numbers of all 0s or all 1s is highly frowned upon and RFC non-compliant.
• Number of Hosts - Refers to the number of effective hosts, excluding the network and broadcast address.

Class A

Network Bits	Subnet Mask	Number of Subnets	Number of Hosts
/8	255.0.0.0	0	16777214
/9	255.128.0.0	2 (0)	8388606
/10	255.192.0.0	4 (2)	4194302
/11	255.224.0.0	8 (6)	2097150
/12	255.240.0.0	16 (14)	1048574
/13	255.248.0.0	32 (30)	524286
/14	255.252.0.0	64 (62)	262142
/15	255.254.0.0	128 (126)	131070
/16	255.255.0.0	256 (254)	65534
/17	255.255.128.0	512 (510)	32766
/18	255.255.192.0	1024 (1022)	16382
/19	255.255.224.0	2048 (2046)	8190
/20	255.255.240.0	4096 (4094)	4094
/21	255.255.248.0	8192 (8190)	2046
/22	255.255.252.0	16384 (16382)	1022
/23	255.255.254.0	32768 (32766)	510
/24	255.255.255.0	65536 (65534)	254
/25	255.255.255.128	131072 (131070)	126
/26	255.255.255.192	262144 (262142)	62
/27	255.255.255.224	524288 (524286)	30
/28	255.255.255.240	1048576 (1048574)	14
/29	255.255.255.248	2097152 (2097150)	6
/30	255.255.255.252	4194304 (4194302)	2

 

Class B

Network Bits	Subnet Mask	Number of Subnets	Number of Hosts
/16	255.255.0.0	0	65534
/17	255.255.128.0	2 (0)	32766
/18	255.255.192.0	4 (2)	16382
/19	255.255.224.0	8 (6)	8190
/20	255.255.240.0	16 (14)	4094
/21	255.255.248.0	32 (30)	2046
/22	255.255.252.0	64 (62)	1022
/23	255.255.254.0	128 (126)	510
/24	255.255.255.0	256 (254)	254
/25	255.255.255.128	512 (510)	126
/26	255.255.255.192	1024 (1022)	62
/27	255.255.255.224	2048 (2046)	30
/28	255.255.255.240	4096 (4094)	14
/29	255.255.255.248	8192 (8190)	6
/30	255.255.255.252	16384 (16382)	2

 

Class C

Network Bits	Subnet Mask	Number of Subnets	Number of Hosts
/24	255.255.255.0	0	254
/25	255.255.255.128	2 (0)	126
/26	255.255.255.192	4 (2)	62
/27	255.255.255.224	8 (6)	30
/28	255.255.255.240	16 (14)	14
/29	255.255.255.248	32 (30)	6
/30	255.255.255.252	64 (62)	2

 

Class D

CIDR Block	Supernet Mask	Number of Class C Addresses	Number of Hosts
/14	255.252.0.0	1024	262144
/15	255.254.0.0	512	131072
/16	255.255.0.0	256	65536
/17	255.255.128.0	128	32768
/18	255.255.192.0	64	16384
/19	255.255.224.0	32	8192
/20	255.255.240.0	16	4096
/21	255.255.248.0	8	2048
/22	255.255.252.0	4	1024
/23	255.255.254.0	2	512