/24 vs /25 — Subnet Comparison
A /24 subnet is 2× larger than a /25. Every additional bit in the prefix halves the address space — the 1-bit difference between these two means /24 has 21 = 2 times as many addresses.
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
126 usable hosts — half a /24
Typical Uses
- →Public vs private half of a /24
- →Department sub-segment
- →Smaller cloud application subnets
Key Differences
How 2 /25 Subnets Divide a /24
Example using 10.0.0.0/24 as the parent block.
| # | CIDR | Network | First Usable | Last Usable | Broadcast | Hosts |
|---|---|---|---|---|---|---|
| 1 | 10.0.0.0/25 | 10.0.0.0 | 10.0.0.1 | 10.0.0.126 | 10.0.0.127 | 126 |
| 2 | 10.0.0.128/25 | 10.0.0.128 | 10.0.0.129 | 10.0.0.254 | 10.0.0.255 | 126 |
FAQ
What is the difference between /24 and /25?
A /24 has 254 usable hosts
and a /25 has 126.
The subnet masks differ: /24 uses 255.255.255.0
while /25 uses 255.255.255.128.
Every additional bit in the prefix halves the number of addresses — so the 1-bit gap means
/24 is exactly 2× larger.
How many /25 subnets fit in a /24?
Exactly 2 /25 subnets fit perfectly inside one /24 with no wasted space. To split a /24 into /25s, just increment the last 1 bit of the network address for each new subnet.
Which should I choose?
/24 is typically used for: Standard subnet — home, office, cloud. /25 is better for: Half a /24 — public/private split. Choose the smallest prefix that comfortably fits your host count — over-allocating wastes address space, but under-allocating means painful renumbering later.