/16 Subnet
65K IPs — standard VPC or site block
A /16 is one of the most commonly used prefix lengths in cloud and enterprise networking. At 65,536 total addresses, it comfortably serves a medium-to-large site or a cloud VPC. AWS default VPC is 172.31.0.0/16.
Common Use Cases
- → AWS / Azure VPC or VNet CIDR
- → Enterprise campus or data centre segment
- → Docker overlay network
- → Kubernetes cluster network
Example /16 Networks
| CIDR | Network | First Usable | Last Usable | Broadcast | Hosts |
|---|---|---|---|---|---|
| 10.0.0.0/16 | 10.0.0.0 | 10.0.0.1 | 10.0.255.254 | 10.0.255.255 | 65,534 |
| 172.16.0.0/16 | 172.16.0.0 | 172.16.0.1 | 172.16.255.254 | 172.16.255.255 | 65,534 |
| 172.31.0.0/16 | 172.31.0.0 | 172.31.0.1 | 172.31.255.254 | 172.31.255.255 | 65,534 |
| 192.168.0.0/16 | 192.168.0.0 | 192.168.0.1 | 192.168.255.254 | 192.168.255.255 | 65,534 |
| 192.168.0.0/16 | 192.168.0.0 | 192.168.0.1 | 192.168.255.254 | 192.168.255.255 | 65,534 |
| 10.0.0.0/16 | 10.0.0.0 | 10.0.0.1 | 10.0.255.254 | 10.0.255.255 | 65,534 |
How /16 Compares
| Prefix | Total IPs | Usable Hosts | Subnet Mask | Typical Use |
|---|---|---|---|---|
| /13 | 524,288 | 524,286 | 255.248.0.0 | — |
| /14 | 262,144 | 262,142 | 255.252.0.0 | — |
| /15 | 131,072 | 131,070 | 255.254.0.0 | — |
| /16 ◀ | 65,536 | 65,534 | 255.255.0.0 | Cloud VPC CIDR, campus network |
| /17 | 32,768 | 32,766 | 255.255.128.0 | Large segment within a /16 |
| /18 | 16,384 | 16,382 | 255.255.192.0 | VPC segment |
| /19 | 8,192 | 8,190 | 255.255.224.0 | — |
Frequently Asked Questions
How many IPs are in a /16?
A /16 subnet contains 65,536 total IP addresses and 65,534 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 /16?
The subnet mask for a /16 is 255.255.0.0.
In CIDR notation, the prefix length /16 means
the first 16 bits of the address are the network portion.
The wildcard (inverse) mask is 0.0.255.255.
How many /16 subnets fit in a /15?
Exactly 2 — a /15 can be split into two /16 subnets of equal size.