CIDR Subnet Splitter
Split a network into equal child subnets by count or target prefix length.
Split Mode
Parent Network
Quick Examples
About CIDR Subnet Splitting
CIDR subnet splitting divides a larger network (parent) into smaller networks (children) of equal size. This is essential for efficient IP address allocation and network design.
Split by Count
Specify how many equal subnets you need. The tool calculates the required prefix length and creates exactly that many subnets (rounded up to the nearest power of 2).
192.168.1.0/24 → 4 subnets192.168.1.0/26192.168.1.64/26192.168.1.128/26192.168.1.192/26Split by Prefix
Specify the target prefix length for child subnets. The tool creates all possible subnets at that prefix length within the parent network.
10.0.0.0/16 → /20 subnets10.0.0.0/20 (16 subnets)10.0.16.0/2010.0.32.0/20... and 13 more
Key Concepts
Power of 2 Rule
Network splitting always results in a power-of-2 number of subnets due to binary addressing.
Prefix Length
Child subnets always have a longer prefix (smaller network) than the parent.
Address Space
All child subnets combined exactly equal the parent's address space.
Binary Boundaries
Subnet boundaries align with binary bit boundaries for efficient routing.
Common Use Cases
- Office Networks: Split a /24 into department subnets
- Cloud VPCs: Create isolated subnets for different tiers
- VLSM Design: Plan hierarchical network addressing
- Data Centers: Segment networks for different services
Technical Notes
IPv4 vs IPv6
IPv4 uses 32-bit addresses with /0-/32 prefixes. IPv6 uses 128-bit addresses with /0-/128 prefixes. The splitting logic is identical for both.
Network vs Host Addresses
In IPv4, the first address is the network address and the last is the broadcast address. IPv6 doesn't have broadcast, so the first and last addresses are both usable.