A /23 is two /24s side by side: 512 addresses, 510 usable, mask 255.255.254.0. It’s the usual next step when a 254-host network runs out. One catch: in a /23, an address ending in .255 or .0 can be a normal host. 192.168.0.255 is a valid host in 192.168.0.0/23, which surprises people used to /24s.
Facts
- Prefix
- /23
- Subnet mask
- 255.255.254.0
- Wildcard mask
- 0.0.1.255
- Binary mask
- 11111111.11111111.11111110.00000000
- Total addresses
- 512
- Usable hosts
- 510
- Example range
- 192.168.0.0/23: 192.168.0.0 – 192.168.1.255
- Typical use
- Office networks that outgrew a /24.
Try it
Try: , ,
- CIDR block
- 192.168.0.0/23
- IP range
- 192.168.0.0 – 192.168.1.255
- Addresses
- 512
- Usable hosts
- 510
- Subnet mask
- 255.255.254.0
- Wildcard mask
- 0.0.1.255
Frequently asked questions
How many hosts are in a /23?
A /23 has 512 addresses. Subtracting the network and broadcast addresses leaves 510 usable hosts.
What is the subnet mask for /23?
/23 is 255.255.254.0 (wildcard mask 0.0.1.255). In binary that’s 23 ones followed by 9 zeros.