Subnet Ninja /16 Subnet Mask
A /16 subnet mask is 255.255.0.0. It has 65,536 addresses, 65,534 usable hosts and the wildcard mask 0.0.255.255.
| CIDR prefix | /16 |
|---|---|
| Subnet mask | 255.255.0.0 |
| Wildcard mask | 0.0.255.255 |
| Binary mask | 11111111.11111111.00000000.00000000 |
| Total addresses | 65,536 |
| Usable hosts | 65,534 |
| Block size | 1 (second octet) |
Example: 172.16.0.0/16
| Network address | 172.16.0.0 |
|---|---|
| First usable host | 172.16.0.1 |
| Last usable host | 172.16.255.254 |
| Broadcast address | 172.16.255.255 |
Where /16 subnets start
/16 networks start on multiples of 1 in the second octet (0, 1, 2, 3, …). A /16 is one block of the private range 172.16.0.0/12, which holds 16 of them.
How to calculate a /16 subnet
- Host bits: 32 − 16 = 16.
- Total addresses: 216 = 65,536.
- Usable hosts: 65,536 − 2 = 65,534, because the network and broadcast addresses can't be assigned to hosts.
- Subnet mask: 16 one-bits followed by 16 zero-bits. The second octet is 255 (256 − 1), which gives 255.255.0.0.
- Wildcard mask: 255.255.255.255 − 255.255.0.0 = 0.0.255.255.
When to use a /16
A /16 is commonly used as the address space for a whole site or cloud network, then split into smaller subnets. Its 65,534 usable hosts are far more than a single broadcast domain should hold.
Updated . Calculate any network with the subnet calculator, or compare all prefixes in the subnet cheat sheet.