Free tool
NetworkingIPv4 Subnet Calculator
Subnet any IPv4 address with CIDR or a dotted mask. Instantly see network, broadcast, and usable hosts, built for CCNA practice and real LAN planning.
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Free toolSubnetting an IPv4 address is one of the first skills every networking student must master, and it is still one of the checks experienced engineers run before they push a change. This free IPv4 subnet calculator turns an address plus a CIDR prefix or subnet mask into the network address, broadcast address, first and last usable IP, and host count in a fraction of a second. Use it for home networks, Cisco lab topologies, and subnetting practice, then work the same problem by hand so the exam feels familiar.
How to use the IPv4 Subnet Calculator
- 1
Enter an IPv4 address, for example 192.168.1.0 or any host inside the subnet.
- 2
Enter a CIDR prefix such as /24 or a dotted mask such as 255.255.255.0.
- 3
Read the network address, broadcast, usable host range, and totals as you type, no sign-up required.
Why IPv4 subnetting still matters
A flat network does not scale. As soon as you add more than a handful of devices, you need logical boundaries for broadcast control, security policy, and cleaner troubleshooting. That is why CCNA and Network+ test subnetting so heavily. If you cannot find the network address of an IPv4 address or calculate usable hosts confidently, VLANs, ACLs, and routing become harder to reason about.
IPv4 subnetting example
Take 192.168.10.0/26. The calculator returns network 192.168.10.0, broadcast 192.168.10.63, first usable IP 192.168.10.1, last usable IP 192.168.10.62, and 62 usable hosts. That is a classic Cisco networking drill and a realistic size for a small office VLAN.
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