Frequently asked questions
What is CIDR notation?
CIDR (Classless Inter-Domain Routing) writes a network as an IP address followed by a slash and a prefix length, like 192.168.1.0/24. The prefix says how many of the 32 bits identify the network; the rest identify hosts.
How many hosts are in a /24 subnet?
A /24 has 256 addresses. Two are reserved (network and broadcast), leaving 254 usable host addresses.
What is a wildcard mask?
A wildcard mask is the inverse of the subnet mask, used in router access control lists (for example on Cisco devices). For a /24 the subnet mask is 255.255.255.0 and the wildcard mask is 0.0.0.255.
How do I split a network into equal subnets?
Increase the prefix length. Each extra bit doubles the number of subnets and halves their size: a /24 splits into two /25s, four /26s, eight /27s, and so on.
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