How Many IPs in a /23?
512 addresses, 510 usable, mask 255.255.254.0.
A /23 joins two /24 networks, a handy size when one /24 is too small but a /22 would be wasteful.
| Subnet mask | 255.255.254.0 |
|---|---|
| Wildcard mask | 0.0.1.255 |
| Total addresses | 512 |
| Usable hosts | 510 |
| In /24 terms | It contains 2 /24 networks. |
| Example (10.0.0.0/23) | 10.0.0.0 - 10.0.1.255 |
Usable addresses in cloud subnets
Cloud providers reserve extra addresses in every subnet, so fewer than 510 are available to your machines.
| AWS | 507 usable |
|---|---|
| Azure | 507 usable |
| Google Cloud | 508 usable |
| Oracle Cloud | 509 usable |
Limits and reserved counts are commonly documented values; check your provider's current documentation before you plan around them.
Other sizes
/22 | /23 | /25 | /26 | /27 | /28
Split a block into /23 subnets with the subnet splitter, or calculate any block with the CIDR calculator.
FAQ
How many usable IP addresses are in a /23?
510 usable addresses out of 512. The network and broadcast addresses are reserved.
What is the subnet mask for /23?
255.255.254.0, with wildcard mask 0.0.1.255.
How many usable addresses does a /23 have in AWS?
507, because AWS reserves five addresses in every subnet.