Subnet Mask
/28 Subnet Mask
A /28 prefix means the subnet mask is 255.255.255.240. It has 4 host bits, giving 16 total addresses and 14 usable hosts.
/28 at a glance
| Property | Value |
|---|---|
| CIDR prefix | /28 |
| Subnet mask | 255.255.255.240 |
| Wildcard mask | 0.0.0.15 |
| Total addresses | 16 |
| Usable hosts | 14 |
| Host bits | 4 |
How it is calculated
A /28 sets the first 28 bits to 1 (network) and the remaining 4 bits to 0 (host). Usable hosts = 24 − 2 = 14.
The wildcard mask 0.0.0.15 is the inverse — used in Cisco ACLs and OSPF network statements.
Frequently asked questions
What is a /28 subnet mask?
A /28 equals 255.255.255.240 in dotted decimal (wildcard 0.0.0.15). It provides 16 total addresses and 14 usable hosts.
How many hosts are in a /28?
A /28 has 4 host bits, so it supports 14 usable hosts.
What is the wildcard mask for /28?
The wildcard (inverse) mask for /28 is 0.0.0.15, used in Cisco ACLs and OSPF statements.
Related
Learn networking hands-on
Master IP addressing, subnetting and Cisco configuration on real lab devices with placement support at Attila Technologies, Ahmedabad.