/24 planner
List the customers, point-to-point links and LANs that need addresses. The planner fits them into one /24 with the largest blocks first, shows the result on a 256-square map, and lists what is left free.
Runs in your browser. Nothing you enter or upload is sent to us.
How to use it
Three steps
- Enter your /24. For example 203.0.113.0/24.
- List what needs addresses. Give each row a name and either the number of hosts it needs or a fixed block size. Use the buttons to add common sizes such as a customer /29 or a link /30.
- Check the map. The largest blocks are placed first, each on its correct boundary, so the free space stays in as few pieces as possible. Download the plan as CSV when you are happy.
Questions
Good to know
How does it choose the block size?
For each row it picks the smallest block whose usable hosts cover the number you enter. For example 12 hosts need a /28 (14 usable) and 50 hosts need a /26 (62 usable). One host gets a /32.
Why are the largest blocks placed first?
Every block must start on a multiple of its own size. Placing large blocks first keeps the gaps between small blocks to a minimum, so more of the /24 stays usable in one piece.
Should I use /30 or /31 for links?
A /30 has two usable addresses plus network and broadcast. A /31 uses both of its two addresses (RFC 3021) and saves space, if both ends of the link support it.
Can I plan more than a /24?
This planner works on one /24 at a time, which is how most ISPs hand out space. For a /22, plan each of its four /24s.
How does IPAM Enterprise help after planning?
In the portal each /24 pool is shown as a 256-square map. You assign blocks to customers, circuits and devices, and the portal stops two people from taking the same block.
More free tools
Other tools you may need
IP spreadsheet checker
Find duplicates, overlaps and typos in an Excel or CSV list.
Open the toolAddress in subnet check
Find which of your blocks holds each address.
Open the toolIPv4 subnet calculator
Network, broadcast, usable range and masks for any block.
Open the toolIPv6 subnet calculator
First and last address, size, /64 count and reverse zone.
Open the toolSubnet mask cheat sheet
Every prefix from /8 to /32 with masks and host counts.
Open the toolCIDR and range converter
Turn first-to-last ranges into CIDR blocks, and back.
Open the tool
Still tracking IPs in a spreadsheet?
IPAM Enterprise keeps every /24, block, customer and circuit in one portal, and checks each assignment for overlaps before it is saved.