Subnet Splitter
Split larger IPv4 CIDR ranges into smaller subnet blocks with copy-ready output for practical network planning workflows.
Input
Split an IPv4 CIDR block into smaller subnets using a target prefix length.
Result
Parent network details, generated subnet count, and copy-ready child subnet list.
What this means
The parent network 172.16.0.0/16 was divided into 16 child subnet(s) at prefix /20.
Each generated subnet has mask 255.255.240.0, 4,096 total address(es), and 4,094 usable host address(es).
Use this tool to plan VLAN segmentation, environment isolation, branch allocations, firewall objects, route summaries, and IPAM updates before applying changes in production.
Common presets
Subnet splitting quick guide
Practical reminders for subnet division and network planning.
Larger prefix means smaller subnet
Moving from /24 to /27 increases the prefix length and creates smaller child networks.
Every split multiplies networks
The number of child subnets depends on the prefix gap between the parent network and the target subnet size.
Plan around actual use
Choose subnet sizes based on host demand, growth margin, segmentation needs, and operational simplicity.
Common use cases
Typical situations where subnet splitting is needed.
Break a larger allocation into smaller segments for VLANs, departments, environments, or branch sites.
Prepare cleaner address plans for cloud landing zones, on-prem networks, and hybrid environments.
Validate subnetting decisions before applying them to firewalls, route tables, and IPAM workflows.