IPv4 prefix set intersect

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

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

Use when you need to: intersection of two ipv4 prefix sets · cidr blocks common to two ipv4 sets · addresses covered by both prefix sets.

Decide before calling

Read the versioned contract and the supported scope below. Reuse ipv4-prefix-set-intersect@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-intersect@1.0.0 for intersection 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

intersection of two ipv4 prefix sets
cidr blocks common to two ipv4 sets
addresses covered by both prefix sets
overlap of two ipv4 prefix lists as cidrs
shared coverage of ipv4 prefix sets
prefix set meet operation
keep only overlapping ipv4 prefixes

Not supported

IPv6 prefix sets
a yes or no overlap flag for exactly two prefixes
non-contiguous wildcard bit masks

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 intersection.
prefixes is the shortest list of non-overlapping CIDRs, sorted by network address, whose addresses are exactly the intersection. The list is empty when the sets are disjoint. 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. Intersecting with an empty set yields an empty cover.

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": [
    "10.0.0.0/8"
  ],
  "right": [
    "10.2.0.0/16",
    "11.0.0.0/8"
  ]
}

Response:

{
  "result": {
    "prefixes": [
      "10.2.0.0/16"
    ],
    "count": 1
  }
}

How to call it

MCP

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

{
  "id": "ipv4-prefix-set-intersect",
  "version": "1.0.0",
  "input": {
    "left": [
      "10.0.0.0/8"
    ],
    "right": [
      "10.2.0.0/16",
      "11.0.0.0/8"
    ]
  }
}

HTTP (no key)

curl -X POST https://computefirst.net/v1/tools/ipv4-prefix-set-intersect/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"left":["10.0.0.0/8"],"right":["10.2.0.0/16","11.0.0.0/8"]}'

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

CLI

node cli.mjs run ipv4-prefix-set-intersect 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 union: Union 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 range to cidrs: Convert an arbitrary IPv4 address range into the minimal list of CIDR blocks that exactly covers it.
IPv4 CIDR overlap: Test whether two IPv4 CIDR blocks overlap (share at least one address).
IPv4 CIDR parse: Parse an IPv4 CIDR block into its network, broadcast, netmask, wildcard mask, usable host range and address counts.