/28 vs /30 — Subnet Comparison
A /28 subnet is 4× larger than a /30. Every additional bit in the prefix halves the address space — the 2-bit difference between these two means /28 has 22 = 4 times as many addresses.
14 usable hosts — tiny segment
Typical Uses
- →AWS VPC endpoint subnet
- →NAT gateway dedicated subnet
- →Small server cluster
2 usable hosts — point-to-point link
Typical Uses
- →WAN point-to-point link between routers
- →BGP peering session
- →Dedicated leased line addressing
Key Differences
How 4 /30 Subnets Divide a /28
Example using 10.0.0.0/28 as the parent block.
| # | CIDR | Network | First Usable | Last Usable | Broadcast | Hosts |
|---|---|---|---|---|---|---|
| 1 | 10.0.0.0/30 | 10.0.0.0 | 10.0.0.1 | 10.0.0.2 | 10.0.0.3 | 2 |
| 2 | 10.0.0.4/30 | 10.0.0.4 | 10.0.0.5 | 10.0.0.6 | 10.0.0.7 | 2 |
| 3 | 10.0.0.8/30 | 10.0.0.8 | 10.0.0.9 | 10.0.0.10 | 10.0.0.11 | 2 |
| 4 | 10.0.0.12/30 | 10.0.0.12 | 10.0.0.13 | 10.0.0.14 | 10.0.0.15 | 2 |
FAQ
What is the difference between /28 and /30?
A /28 has 14 usable hosts
and a /30 has 2.
The subnet masks differ: /28 uses 255.255.255.240
while /30 uses 255.255.255.252.
Every additional bit in the prefix halves the number of addresses — so the 2-bit gap means
/28 is exactly 4× larger.
How many /30 subnets fit in a /28?
Exactly 4 /30 subnets fit perfectly inside one /28 with no wasted space. To split a /28 into /30s, just increment the last 2 bits of the network address for each new subnet.
Which should I choose?
/28 is typically used for: AWS NAT/endpoint dedicated subnet. /30 is better for: WAN point-to-point link. Choose the smallest prefix that comfortably fits your host count — over-allocating wastes address space, but under-allocating means painful renumbering later.