/23 vs /24 — Subnet Comparison
A /23 subnet is 2× larger than a /24. Every additional bit in the prefix halves the address space — the 1-bit difference between these two means /23 has 21 = 2 times as many addresses.
512 IPs — two /24s combined
Typical Uses
- →Two-floor office network
- →Expanded department VLAN
- →Route aggregation of two /24s
254 usable hosts — the industry standard
Typical Uses
- →Home and SOHO LAN (192.168.1.0/24)
- →Standard office VLAN
- →AWS/Azure subnet per AZ
Key Differences
How 2 /24 Subnets Divide a /23
Example using 10.0.0.0/23 as the parent block.
| # | CIDR | Network | First Usable | Last Usable | Broadcast | Hosts |
|---|---|---|---|---|---|---|
| 1 | 10.0.0.0/24 | 10.0.0.0 | 10.0.0.1 | 10.0.0.254 | 10.0.0.255 | 254 |
| 2 | 10.0.1.0/24 | 10.0.1.0 | 10.0.1.1 | 10.0.1.254 | 10.0.1.255 | 254 |
FAQ
What is the difference between /23 and /24?
A /23 has 510 usable hosts
and a /24 has 254.
The subnet masks differ: /23 uses 255.255.254.0
while /24 uses 255.255.255.0.
Every additional bit in the prefix halves the number of addresses — so the 1-bit gap means
/23 is exactly 2× larger.
How many /24 subnets fit in a /23?
Exactly 2 /24 subnets fit perfectly inside one /23 with no wasted space. To split a /23 into /24s, just increment the last 1 bit of the network address for each new subnet.
Which should I choose?
/23 is typically used for: Aggregated /24 pair. /24 is better for: Standard subnet — home, office, cloud. Choose the smallest prefix that comfortably fits your host count — over-allocating wastes address space, but under-allocating means painful renumbering later.