/23 Subnet Mask

/23 subnet mask is a subnet mask with 255.255.254.0 as the dotted decimal notation and 0.0.1.255 as the wildcard mask.

/23 subnet mask divide larger network like class B network and Class A networks into a smaller networks(subnetworks). Each of the subnetworks has 512 range of IP addresses. The first IP address in this range is the network address and the last IP address in this range is the broadcast IP address. Hence, there are 510 usable IP addresses in a /23 subnet mask.

A /23 network can be further subneted with a /24 subnet mask, a /25 subnet mask, a /26 subnet subnet, and higher prefix lengths, which we covered earlier.

For example, If we subnet the network; 192.168.0.0/16 which is a class B network with a /23 subnet mask, the network address for the first subnet is 192.168.0.0, the usable IP address range is 192.168.0.1 to 192.168.1.254 and the broadcast IP address is 192.168.1.255. The network address for the second subnet is 192.168.2.0, the usable IP range is 192.168.2.1 to 192.168.3.254 and the broadcast IP address is 192.168.3.255.

Here is a table of class B network subnetted with a /23 subnet mask;

Network AddressUsable IP RangeBroadcast IP
192.168.0.0192.168.0.1 - 192.168.1.254192.168.1.255
192.168.2.0192.168.2.1 - 192.168.3.254192.168.3.255
192.168.4.0192.168.4.1 - 192.168.5.254192.168.5.255
192.168.6.0192.168.6.1 - 192.168.7.254192.168.7.255
.........
192.168.250.0192.168.250.1 - 192.168.251.254192.168.251.255
192.168.252.0192.168.252.1 - 192.168.253.254192.168.253.255
192.168.254.0192.168.254.1 - 192.168.255.254192.168.255.255

/23 Subnet Mask Usable IP Address

There are 512 ranges of IP addresses in a /23 subnet mask. The first in this range is the network address, and the last in this range is the broadcast IP address. Hence, there are 510 usable IP addresses in a /23 subnet mask.

/23 Subnet Mask Dotted Decimal Notation

The dotted decimal notation for a /23 subnet mask is 255.255.254.0 This value is gotten by setting the first 23 bits of the 32-bit IPv4 address to ‘1s’, setting the remaining 9 bits to ‘0s’, and converting from binary to decimals.

Dotted decimal notation for /23 subnet mask

Subnetting Class B Network with /23 Subnet Mask

To subnet a Class B network with a /23 subnet mask, 7 bits need to be borrowed from the host bits and added to the network bits.

subnetting class B network with /23 prefix length

When subnetting a Class B network with a /23 prefix length, 128 subnetworks are derived from the calculation 2^7 = 128, where 7 represents the number of borrowed bits for subnetting. It’s important to note that according to RFC guidelines, the first and last subnetworks resulting from this subnetting process cannot be utilized. These reserved subnetworks serve specific functions and are excluded from regular use within the subnetted space.

Subnetting Class A Network with /23 Subnet Mask

For a class A network to be subnetted with a /23 prefix length, 15 bits need to be borrowed from host bits and added to the network bits.

subnetting Class A network with /23 subnet mask

When subnetting a Class A network with a /23 prefix length, 32769 subnetworks are obtainable. This comes from the calculation 2^15 = 32769, where 15 represents the number of borrowed bits for subnetting.

It’s important to note that according to RFC guidelines, the first and last subnetworks resulting from this subnetting process cannot be utilized. These reserved subnetworks serve specific functions and are excluded from regular use. Hence, there are 32767 usable subnetworks.

How Many host in /23

There are 512 ranges of IP addresses in a /23 prefix length; the first IP address in this range is the network ID, and the last IP address in this range is the broadcast address. Hence, there are 510 IP addresses available to be assigned to a host in a /23 subnet mask.

Related Contents
/16 subnet maskEverything About /24 Subnet Mask
Everything About /17 Subnet Mask/25 Subnet Mask
Everything About /18 Subnet Mask/26 Subnet Mask
Everything About /19 Subnet Mask/27 Subnet Mask
Everything About /20 Subnet Mask/30 Subnet Mask
/21 Subnet Mask | /21 IP Range/31 Subnet Mask
/22 Subnet Mask/32 Subnet Mask
/23 Subnet Mask/28 Subnet Mask
/29 Subnet Mask
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