/27 Subnet: Mask 255.255.255.224, 30 Usable Hosts

A /27 subnet has a subnet mask of 255.255.255.224 and contains 32 total IP addresses, of which 30 are usable host addresses (the network and broadcast addresses are reserved). 8 /27 networks fit inside a single /24.

Usable hosts in a /27 by platform

Cloud providers reserve more than the usual two addresses per subnet, so the same /27 gives you fewer usable IPs in the cloud than on a standard LAN.

Good to know

A /27 (30 usable hosts) splits a /24 into eight. Often used for small VLANs, management networks, or a handful of servers.

How a /27 is calculated

• The /27 means the first 27 bits are the network portion, leaving 5 host bits.
• Total addresses = 2^(32 - 27) = 2^5 = 32.
• Usable hosts (standard) = 32 - 2 (network + broadcast) = 30.
• Subnet mask = 255.255.255.224; wildcard mask = 0.0.0.31.