/23 Subnet Mask (255.255.254.0)

/23 subnet summary
Prefix/23
Subnet mask255.255.254.0
Wildcard mask0.0.1.255
Binary mask11111111.11111111.11111110.00000000
Total addresses512
Usable hosts510
Host bits9
Subnets of /23 in a /16128

e.g. 10.0.0.5/22 or 10.0.0.5 255.255.252.0

Network address172.16.0.0
Broadcast address172.16.1.255
First usable host172.16.0.1
Last usable host172.16.1.254
Total addresses512
Usable hosts510
Subnet mask255.255.254.0
Wildcard mask0.0.1.255
CIDR notation172.16.0.0/23
IP classClass B (legacy)
Address typePrivate (RFC 1918)
IP address (binary)10101100.00010000.00000000.00000000
Subnet mask (binary)11111111.11111111.11111110.00000000

■ network bits ■ host bits

Runs entirely in your browser. Nothing you enter is sent to a server.

What is a /23 subnet?

A /23 subnet uses the first 23 bits of an IPv4 address for the network and leaves 9 bits for hosts. Its subnet mask is 255.255.254.0, and it contains 2⁹ = 512 addresses, of which 510 can be assigned to devices. Typical use: Two /24s combined; used when a VLAN outgrows 254 hosts. Use the subnet calculator above to check any /23 network.

/23 subnet example

For 172.16.0.0/23: network address 172.16.0.0, usable hosts 172.16.0.1 – 172.16.1.254, broadcast address 172.16.1.255, wildcard mask 0.0.1.255.

/23 networks in 172.16.0.0/16

A /16 holds 128 /23 networks:

Frequently asked questions

How many usable IPs are in a /23?

510. The block has 512 addresses; the first is the network address and the last is the broadcast address.

What is the subnet mask for /23?

255.255.254.0, or 11111111.11111111.11111110.00000000 in binary.

How many /23 subnets are in a /16?

128 (2⁷), because a /23 uses 7 more network bits than a /16.

What is the difference between /23 and /22?

A /22 (255.255.252.0) is twice as large: 1,024 addresses and 1,022 usable hosts, spanning two consecutive /23 blocks such as 172.16.0.0–172.16.3.255.

Nearby prefixes