/27 vs /28 — Subnet Comparison
A /27 subnet is 2× larger than a /28. Every additional bit in the prefix halves the address space — the 1-bit difference between these two means /27 has 21 = 2 times as many addresses.
30 usable hosts — small workgroup
Typical Uses
- →Small workgroup LAN
- →Network device management subnet
- →Cloud NAT gateway subnet
14 usable hosts — tiny segment
Typical Uses
- →AWS VPC endpoint subnet
- →NAT gateway dedicated subnet
- →Small server cluster
Key Differences
How 2 /28 Subnets Divide a /27
Example using 10.0.0.0/27 as the parent block.
| # | CIDR | Network | First Usable | Last Usable | Broadcast | Hosts |
|---|---|---|---|---|---|---|
| 1 | 10.0.0.0/28 | 10.0.0.0 | 10.0.0.1 | 10.0.0.14 | 10.0.0.15 | 14 |
| 2 | 10.0.0.16/28 | 10.0.0.16 | 10.0.0.17 | 10.0.0.30 | 10.0.0.31 | 14 |
FAQ
What is the difference between /27 and /28?
A /27 has 30 usable hosts
and a /28 has 14.
The subnet masks differ: /27 uses 255.255.255.224
while /28 uses 255.255.255.240.
Every additional bit in the prefix halves the number of addresses — so the 1-bit gap means
/27 is exactly 2× larger.
How many /28 subnets fit in a /27?
Exactly 2 /28 subnets fit perfectly inside one /27 with no wasted space. To split a /27 into /28s, just increment the last 1 bit of the network address for each new subnet.
Which should I choose?
/27 is typically used for: Small workgroup / management subnet. /28 is better for: AWS NAT/endpoint dedicated subnet. Choose the smallest prefix that comfortably fits your host count — over-allocating wastes address space, but under-allocating means painful renumbering later.