/30 Subnet: Mask 255.255.255.252, 2 Usable Hosts

A /30 subnet has a subnet mask of 255.255.255.252 and contains 4 total IP addresses, of which 2 are usable host addresses (the network and broadcast addresses are reserved). 64 /30 networks fit inside a single /24.

Usable hosts in a /30 by platform

Cloud providers reserve more than the usual two addresses per subnet, so the same /30 gives you fewer usable IPs in the cloud than on a standard LAN.

Good to know

A /30 (2 usable hosts) is the classic point-to-point link size, one address for each end of a router-to-router connection.

How a /30 is calculated

• The /30 means the first 30 bits are the network portion, leaving 2 host bits.
• Total addresses = 2^(32 - 30) = 2^2 = 4.
• Usable hosts (standard) = 4 - 2 (network + broadcast) = 2.
• Subnet mask = 255.255.255.252; wildcard mask = 0.0.0.3.