/15 Subnet Mask
A /15 prefix means the subnet mask is 255.254.0.0. It has 17 host bits, giving 131,072 total addresses and 131,070 usable hosts.
/15 at a glance
| Property | Value |
|---|---|
| CIDR prefix | /15 |
| Subnet mask | 255.254.0.0 |
| Wildcard mask | 0.1.255.255 |
| Total addresses | 131,072 |
| Usable hosts | 131,070 |
| Host bits | 17 |
How it is calculated
A /15 sets the first 15 bits to 1 (network) and the remaining 17 bits to 0 (host). Usable hosts = 217 − 2 = 131,070.
The wildcard mask 0.1.255.255 is the inverse — used in Cisco ACLs and OSPF network statements.
Frequently asked questions
What is a /15 subnet mask?
A /15 equals 255.254.0.0 in dotted decimal (wildcard 0.1.255.255). It provides 131,072 total addresses and 131,070 usable hosts.
How many hosts are in a /15?
A /15 has 17 host bits, so it supports 131,070 usable hosts.
What is the wildcard mask for /15?
The wildcard (inverse) mask for /15 is 0.1.255.255, used in Cisco ACLs and OSPF statements.
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