Planning
FLSM calculator — split IPv4 into equal subnets
Split an IPv4 network into equal-sized FLSM subnets. Check prefixes, network addresses, hosts and broadcasts, such as a /24 split into /26 blocks.
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Click an example below the form. Look at the result, then change one value to compare what happens.
- FLSM
- Dividing a network into equal parts with the same prefix. A /24 split into /26 blocks gives four equal subnets.
- Parent network
- The entire address block available to you. Every new subnet must fit inside it.
01 / Input
Start with your data
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02 / Your result
A result you can understand.
Fill in the form or choose an example. You will see the values and how they were calculated.
02 / Your result
Step by step
How did we get here?
How to use it
Choose the new subnet prefix. For example, splitting a /24 into /26 blocks produces four subnets of 64 addresses each.
A little network lab
Four equal networks for four departments
Split 192.168.1.0/24 into four equal subnets. This works well when each group needs a similar number of addresses.
Four parts are 2², so you need two extra network bits: 24 + 2 = /26.
Each part has 6 host bits: 64 addresses. Networks begin at .0, .64, .128 and .192.
Each ordinary /26 reserves its own network and broadcast addresses, leaving 62 usable hosts. That is 248 in total, versus 254 in an undivided /24.
Your turn
How many /27 subnets fit inside a /24?
Show answer and explanation
Eight: 2^(27 − 24) = 8. Each has 32 addresses, including 30 ordinary usable hosts.
Official documents
Standards & sources
Sources checked:
- CIDR addressing and route aggregation rules (RFC 4632 / BCP 122)
- Two-address /31 point-to-point networks (RFC 3021)
The date refers to checking the listed documents and registries, not endorsement by their authors. Calculation assumptions and limits appear with the result. How we prepare the material.