What is a /28 subnet? 16 IPs for small server groups and point-to-point links

How this is calculated

With 14 usable addresses, a /28 fits a small cluster of web servers, a database HA pair with monitoring, or a dedicated management network. Cloud providers like AWS and Azure let you create /28 subnets within a VPC or VNet, which is useful for security groups that isolate specific application tiers. The subnet mask 255.255.255.240 means each /28 block increments the last octet by 16 (e.g., .0-.15, .16-.31, .32-.47).

Verdict

The /28 mask 255.255.255.240 reserves 28 bits for the network and leaves 4 bits for hosts, which is 16 total addresses minus the network and broadcast reservations, leaving 14 usable. Each /28 block increments the last octet by 16 (.0-.15, .16-.31, .32-.47), which is why /28 is the natural size for small server clusters, DMZ segments, and isolated cloud security groups where you want isolation without burning an entire /24. The growth case matters: if you might add a failover node or a monitoring sidecar later, the 14-host budget absorbs it. For a true point-to-point router link that only needs 2 addresses, drop to a /30 or /31 to save the wasted space.