Subnet Mask
/16 Subnet Mask
A /16 prefix means the subnet mask is 255.255.0.0. It has 16 host bits, giving 65,536 total addresses and 65,534 usable hosts.
/16 at a glance
| Property | Value |
|---|---|
| CIDR prefix | /16 |
| Subnet mask | 255.255.0.0 |
| Wildcard mask | 0.0.255.255 |
| Total addresses | 65,536 |
| Usable hosts | 65,534 |
| Host bits | 16 |
How it is calculated
A /16 sets the first 16 bits to 1 (network) and the remaining 16 bits to 0 (host). Usable hosts = 216 − 2 = 65,534.
The wildcard mask 0.0.255.255 is the inverse — used in Cisco ACLs and OSPF network statements.
Frequently asked questions
What is a /16 subnet mask?
A /16 equals 255.255.0.0 in dotted decimal (wildcard 0.0.255.255). It provides 65,536 total addresses and 65,534 usable hosts.
How many hosts are in a /16?
A /16 has 16 host bits, so it supports 65,534 usable hosts.
What is the wildcard mask for /16?
The wildcard (inverse) mask for /16 is 0.0.255.255, used in Cisco ACLs and OSPF statements.
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