Subnet Mask Table

The following table provides a quick reference guide for subnet masks and their corresponding CIDR notation from /30 up to /8. It helps determine the number of available IP addresses, total network size, and broadcast addresses within a subnet.



CIDR Netmask Total addresses Usable
/30 4 1
/29 8 5
/28 16 13
/27 32 29
/26 64 61
/25 128 125
/24 256 253
/23 512 509
/22 1,024 1,021
/21 2,048 2,045
/20 4,096 4,093
/19 8,192 8,189
/18 16,384 16,381
/17 32,768 32,765
/16 65,536 65,533
/12 1,048,544 1,048,541
/8 16,777,214 16,777,211



The subnet: has 4 addresses - Network Address - Gateway - Usable IP - Broadcast


More information:

  1. Network Address: The network address represents the starting address of a subnet. It is used to identify the network itself and cannot be assigned to a host.
  2. CIDR Notation: CIDR (Classless Inter-Domain Routing) notation represents the subnet mask using a combination of an IP address and a slash ("/") followed by the prefix length. For example, the CIDR notation "" signifies a subnet with a prefix length of 30.

  3. Usable IP Addresses: The usable IP addresses are the range of IP addresses that can be assigned to devices within a subnet. These IP addresses exclude the network and broadcast addresses.

  4. Broadcast Address: The broadcast address represents the last address in a subnet and is used to send a message to all devices within that subnet. It cannot be assigned to a host.

  5. Total IP Addresses: The total IP addresses in a subnet refer to the sum of usable IP addresses, network address, and broadcast address. It provides an overview of the size of the subnet.


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