Developer Tools

Subnet
Calculator

Q: What is the difference between a subnet mask and a wildcard mask?

The subnet mask (e.g. 255.255.255.0) marks the network bits. The wildcard mask is its inverse (0.0.0.255) and is used in ACLs and OSPF to match the host bits.

Q: How many hosts are in a /30?

A /30 has 4 addresses and 2 usable hosts — commonly used for point-to-point links between two routers.

Enter any IPv4 address with a CIDR prefix and instantly get the network, broadcast, usable host range, subnet mask and total hosts.

CIDR /0–/32

Host range

Wildcard mask

# CIDR notation
192.168.1.0/24
# 256 addrs, 254 hosts
net 192.168.1.0
bcast 192.168.1.255
mask 255.255.255.0

Frequently Asked Questions

What is CIDR notation?

CIDR (Classless Inter-Domain Routing) writes a network as an address plus a prefix length, e.g. 192.168.1.0/24. The /24 means the first 24 bits are the network portion, leaving 8 bits (256 addresses) for hosts.

Why are there fewer usable hosts than total addresses?

In each ordinary subnet two addresses are reserved: the first is the network address and the last is the broadcast address. So a /24 has 256 addresses but 254 usable hosts.

What is the difference between a subnet mask and a wildcard mask?

The subnet mask (e.g. 255.255.255.0) marks the network bits. The wildcard mask is its inverse (0.0.0.255) and is used in ACLs and OSPF to match the host bits.

How many hosts are in a /30?

A /30 has 4 addresses and 2 usable hosts — commonly used for point-to-point links between two routers.