IP Subnet Calculator – CIDR, Network & Host Range
Network Address
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Broadcast Address
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First Usable Host
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Last Usable Host
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Usable Hosts
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CIDR Notation
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Subnet Mask
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Wildcard Mask
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Binary Representation (IP)
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Binary Representation (Mask)
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IP Class
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Understanding IP Subnetting and CIDR Notation
IP subnetting is a fundamental networking concept that divides a larger network into smaller, more manageable segments called subnets. Each subnet has its own range of IP addresses, defined by a subnet mask. This calculator lets you enter any IPv4 address along with a subnet mask in dotted-decimal format (such as 255.255.255.0) or CIDR notation (such as /24) and instantly see the full breakdown of that subnet.
The network address is the first address in the subnet and identifies the network itself, while the broadcast address is the last address used to communicate with all hosts on the subnet. Usable host addresses fall between these two. For a /24 network, you get 254 usable addresses. For a /30 network, commonly used for point-to-point links, you get only 2 usable addresses. Understanding these ranges is essential for network planning, firewall rules, and VLAN configuration.
The wildcard mask is the bitwise inverse of the subnet mask and is frequently used in Cisco router access control lists and OSPF area configurations. The binary representation helps visualize exactly which bits belong to the network portion and which belong to the host portion. Whether you are studying for a CCNA certification, configuring a home lab, or planning an enterprise network, this subnet calculator provides all the details you need at a glance.
Frequently Asked Questions
What is a subnet mask?
A subnet mask is a 32-bit number that divides an IP address into network and host portions. It uses consecutive 1-bits for the network part and 0-bits for the host part. For example, 255.255.255.0 (/24) means the first 24 bits identify the network and the remaining 8 bits identify hosts, allowing up to 254 usable addresses.
What is CIDR notation?
CIDR (Classless Inter-Domain Routing) notation is a compact way to express an IP address and its subnet mask. It appends a slash and a number to the IP address, such as 192.168.1.0/24. The number indicates how many bits are used for the network portion.
What is the difference between network and broadcast address?
The network address is the first address in a subnet (all host bits set to 0) and identifies the subnet. The broadcast address is the last address (all host bits set to 1) used to send data to all hosts. Neither can be assigned to a device.
What is a wildcard mask?
A wildcard mask is the inverse of a subnet mask. Where the subnet mask has 1-bits, the wildcard has 0-bits, and vice versa. For example, the wildcard for 255.255.255.0 is 0.0.0.255. Wildcard masks are used in ACLs and OSPF configurations on Cisco routers.