/28 Subnet
14 usable hosts — tiny segment
A /28 is the smallest subnet commonly assigned to end-devices, with 16 addresses and 14 usable hosts. AWS recommends /28 subnets for VPC endpoints, NAT gateways, and transit gateway attachments.
Common Use Cases
- → AWS VPC endpoint subnet
- → NAT gateway dedicated subnet
- → Small server cluster
- → VPN concentrator subnet
Example /28 Networks
| CIDR | Network | First Usable | Last Usable | Broadcast | Hosts |
|---|---|---|---|---|---|
| 10.0.0.0/28 | 10.0.0.0 | 10.0.0.1 | 10.0.0.14 | 10.0.0.15 | 14 |
| 172.16.0.0/28 | 172.16.0.0 | 172.16.0.1 | 172.16.0.14 | 172.16.0.15 | 14 |
| 172.31.0.0/28 | 172.31.0.0 | 172.31.0.1 | 172.31.0.14 | 172.31.0.15 | 14 |
| 192.168.0.0/28 | 192.168.0.0 | 192.168.0.1 | 192.168.0.14 | 192.168.0.15 | 14 |
| 192.168.1.0/28 | 192.168.1.0 | 192.168.1.1 | 192.168.1.14 | 192.168.1.15 | 14 |
| 10.0.1.0/28 | 10.0.1.0 | 10.0.1.1 | 10.0.1.14 | 10.0.1.15 | 14 |
How /28 Compares
| Prefix | Total IPs | Usable Hosts | Subnet Mask | Typical Use |
|---|---|---|---|---|
| /25 | 128 | 126 | 255.255.255.128 | Half a /24 — public/private split |
| /26 | 64 | 62 | 255.255.255.192 | Cloud per-tier subnet, small VLAN |
| /27 | 32 | 30 | 255.255.255.224 | Small workgroup / management subnet |
| /28 ◀ | 16 | 14 | 255.255.255.240 | AWS NAT/endpoint dedicated subnet |
| /29 | 8 | 6 | 255.255.255.248 | Tiny server cluster or infra segment |
| /30 | 4 | 2 | 255.255.255.252 | WAN point-to-point link |
| /31 | 2 | 2 | 255.255.255.254 | Modern P2P links (RFC 3021) |
Frequently Asked Questions
How many IPs are in a /28?
A /28 subnet contains 16 total IP addresses and 14 usable host addresses. The network address (first IP) and broadcast address (last IP) are reserved and cannot be assigned to hosts.
What is the subnet mask for /28?
The subnet mask for a /28 is 255.255.255.240.
In CIDR notation, the prefix length /28 means
the first 28 bits of the address are the network portion.
The wildcard (inverse) mask is 0.0.0.15.
How many /28 subnets fit in a /27?
Exactly 2 — a /27 can be split into two /28 subnets of equal size. Each /28 subnet has 14 usable hosts, compared to 30 in the parent /27.