Subnet mask cheat sheet

This cheat sheet provides a quick reference guide for subnet masks and their corresponding CIDR notation. It helps determine the number of available IP addresses, network, and broadcast addresses within a subnet.

IPv4

 

CIDR Netmask Total addresses Usable
/30 255.255.255.252 4 1
/29 255.255.255.248 8 5
/28 255.255.255.240 16 13
/27 255.255.255.224 32 29
/26 255.255.255.192 64 61
/25 255.255.255.128 128 125
/24 255.255.255.0 256 253
/23 255.255.254.0 512 509
/22 255.255.252.0 1024 1021
/21 255.255.248.0 2048 2045
/20 255.255.240.0 4096 4093
/19 255.255.224.0 8192 8189
/18 255.255.192.0 16384 16381
/17 255.255.128.0 32768 32765
/16 255.255.0.0 65536 65533
/12 255.240.0.0 1048544 1048541
/8 255.0.0.0 16777214 16777211

 

Example:

The subnet: 192.168.5.0/30 has 4 addresses

192.168.5.0 - Network Address

192.168.5.1 - Gateway

192.168.5.2 - Usable IP

192.168.5.3 - 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 "192.168.10.0/30" 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.

 

  • subnet, netmask, mask
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