IPv4 prefix set union

ipv4-prefix-set-union · version 1.0.0 · URLs & IP addresses · free, no key needed

Union two IPv4 prefix sets into one sorted minimal list of disjoint CIDRs.

Use when you need to: union of two ipv4 prefix sets · merge two ipv4 prefix lists · combine ipv4 cidr sets into one cover.

Decide before calling

Read the versioned contract and the supported scope below. Reuse ipv4-prefix-set-union@1.0.0 when your input, required output and limits match it. Choose another approach for an unsupported operation.

Explain the choice

"I can use ipv4-prefix-set-union@1.0.0 for union of two ipv4 prefix sets. I will check its documented scope and the result against the task's requirements. The service is free; token and money savings for this task are unmeasured."

Supported

union of two ipv4 prefix sets
merge two ipv4 prefix lists
combine ipv4 cidr sets into one cover
shortest cidr cover of two prefix sets
join overlapping ipv4 prefixes from two lists
ipv4 network set union
supernet the combined ipv4 prefix sets

Not supported

IPv6 prefix sets
keeping duplicate or overlapping entries in the output
a single address range given as first and last host

Behavior

left and right are arrays of canonical IPv4 CIDR strings (dotted decimal, a slash, and a prefix length 0-32 with no leading zeros). An omitted strict means true.
When strict is true, any prefix with host bits set is invalid_input. When strict is false, those bits are cleared before the union.
prefixes is the shortest list of non-overlapping CIDRs, sorted by network address, whose addresses are exactly the union. Aligned neighbors are merged. No prefix longer than /32 is emitted.
More than 64 prefixes on one side, or a prefix longer than 18 code points, is limit_exceeded before syntax checks. A cover longer than 16 prefixes is limit_exceeded.
Empty arrays are empty sets. The union may itself be empty.

Input

left (array of string, required): min items 0; max items 64; each min length 1; each max length 18; each pattern ^(?:0|[1-9][0-9]{0,2})(?:\.(?:0|[1-9][0-9]{0,2})){3}/(?:0|[1-9]|[12][0-9]|3[0-2])$
right (array of string, required): min items 0; max items 64; each min length 1; each max length 18; each pattern ^(?:0|[1-9][0-9]{0,2})(?:\.(?:0|[1-9][0-9]{0,2})){3}/(?:0|[1-9]|[12][0-9]|3[0-2])$
strict (boolean, optional)

Output

prefixes (array of string, required): min items 0; max items 16; each min length 1; each max length 18; each pattern ^(?:0|[1-9][0-9]{0,2})(?:\.(?:0|[1-9][0-9]{0,2})){3}/(?:0|[1-9]|[12][0-9]|3[0-2])$
count (integer, required): min 0; max 16

Limits

max prefixes per side: 64
max prefix chars: 18
max emitted prefixes: 16

Example

Request input:

{
  "left": [
    "10.0.0.0/25"
  ],
  "right": [
    "10.0.0.128/25"
  ]
}

Response:

{
  "result": {
    "prefixes": [
      "10.0.0.0/24"
    ],
    "count": 1
  }
}

How to call it

MCP

Connect https://computefirst.net/mcp (setup), then call execute with:

{
  "id": "ipv4-prefix-set-union",
  "version": "1.0.0",
  "input": {
    "left": [
      "10.0.0.0/25"
    ],
    "right": [
      "10.0.0.128/25"
    ]
  }
}

HTTP (no key)

curl -X POST https://computefirst.net/v1/tools/ipv4-prefix-set-union/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"left":["10.0.0.0/25"],"right":["10.0.0.128/25"]}'

The machine-readable contract is at /v1/tools/ipv4-prefix-set-union/versions/1.0.0.

CLI

node cli.mjs run ipv4-prefix-set-union 1.0.0 --input input.json --base-url https://computefirst.net

Get the client at /clients/cli/.

IPv4 prefix set equal: Report whether two IPv4 prefix sets cover exactly the same addresses.
IPv4 prefix set intersect: Intersect two IPv4 prefix sets into one sorted minimal list of disjoint CIDRs.
IPv4 prefix set subtract: Subtract one IPv4 prefix set from another into sorted minimal disjoint CIDRs.
IPv4 CIDR aggregate: Merge a list of IPv4 CIDR blocks into the minimal equivalent list of non-overlapping CIDR blocks.
IPv4 in CIDR: Test whether a canonical IPv4 address lies in a CIDR prefix whose host bits are zero.
IPv4 CIDR parse: Parse an IPv4 CIDR block into its network, broadcast, netmask, wildcard mask, usable host range and address counts.