A /23 subnet mask is 255.255.254.0, with 512 addresses and 510 usable hosts.
| CIDR prefix | /23 |
|---|---|
| Subnet mask | 255.255.254.0 |
| Subnet mask (binary) | 11111111.11111111.11111110.00000000 |
| Wildcard mask | 0.0.1.255 |
| Network bits / host bits | 23 / 9 |
| Total addresses | 512 |
| Usable hosts | 510 |
| /23 subnets in a /8 | 32,768 |
| /23 subnets in a /16 | 128 |
The mask ends 7 bits into octet 3, so blocks step in increments of 2 in that octet. Two contiguous /24 networks in one block, a common choice when a /24 runs out of addresses.
| Network | First usable host | Last usable host | Broadcast |
|---|---|---|---|
| 192.168.0.0/23 | 192.168.0.1 | 192.168.1.254 | 192.168.1.255 |
| 192.168.2.0/23 | 192.168.2.1 | 192.168.3.254 | 192.168.3.255 |
| 192.168.4.0/23 | 192.168.4.1 | 192.168.5.254 | 192.168.5.255 |
| 192.168.6.0/23 | 192.168.6.1 | 192.168.7.254 | 192.168.7.255 |
| 192.168.8.0/23 | 192.168.8.1 | 192.168.9.254 | 192.168.9.255 |
| 192.168.10.0/23 | 192.168.10.1 | 192.168.11.254 | 192.168.11.255 |
| 192.168.12.0/23 | 192.168.12.1 | 192.168.13.254 | 192.168.13.255 |
| 192.168.14.0/23 | 192.168.14.1 | 192.168.15.254 | 192.168.15.255 |
A /23 subnet mask is 255.255.254.0. In binary that is 11111111.11111111.11111110.00000000: 23 network bits followed by 9 host bits. The wildcard mask is 0.0.1.255.
A /23 holds 512 addresses in total. Subtracting the network and broadcast addresses leaves 510 usable hosts.
A /16 divides into 128 subnets of size /23, because each extra mask bit doubles the number of subnets.
Calculate this over HTTP: curl https://networkcalc.com/api/ip/192.168.1.0/23.
See the Subnet Calculator API.