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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