IPv4 Wildcard Mask Contiguity Audit
Audit whether an IPv4 wildcard is all trailing one bits and report its equivalent prefix; noncontiguous wildcard masks remain valid patterns but not CIDR masks.
Description
Audit whether an IPv4 wildcard is all trailing one bits and report its equivalent prefix; noncontiguous wildcard masks remain valid patterns but not CIDR masks.
A CIDR-compatible IPv4 wildcard has only a contiguous low-bit run of ones. Other wildcard patterns can still be meaningful outside CIDR.
When to use this tool
Audit whether an IPv4 wildcard is all trailing one bits and report its equivalent prefix; noncontiguous wildcard masks remain valid patterns but not CIDR masks.
- Prepare the supplied wildcard fields for this operation.
- Compare the complete example with the representation used by your own input before carrying the result into another step.
How to use the tool and how it works
- Enter wildcard. Use the exact text syntax, units and index conventions explained below.
- Run the tool. If input validation fails, correct the supplied fields before interpreting any result.
- Read result.contiguous, result.prefix. Interpret false, null and empty lists using the distinctions below; they can be valid outputs.
Parse wildcard as 32 bits. contiguous is true when w AND (w plus one) is zero. When true, prefix is 32 minus the wildcard bit length, with zero handled as /32; otherwise prefix is null.1
| Input field | Meaning and representation | Accepted input |
|---|---|---|
| wildcard | Address text for the family named by this tool. Prefix lengths are separate fields where shown. | Text; at most 8,192 UTF-16 code units, subject to the grammar above |
| Output field | Interpretation |
|---|---|
| result | Object containing the named outputs below. |
| result.contiguous | Flag for contiguous under the exact condition described above. |
| result.prefix | The prefix value under the stated formula or text convention. |
{
"input": {
"wildcard": "0.0.0.255"
},
"output": {
"result": {
"contiguous": true,
"prefix": 24
}
}
}Limitations and assumptions
- This checks wildcard shape, without interpreting an ACL or validating routing and host policies.
- IPv4 input uses strict dotted-decimal octets without leading zeros or surrounding whitespace. IPv6 accepts its supported compressed or full spellings and trims surrounding whitespace, but rejects zone identifiers; embedded dotted IPv4 uses the strict IPv4 spelling. IPv6 address outputs are fully expanded unless stated otherwise.
- All declared input fields are required and unexpected top-level fields are rejected. Numbers must be finite; lists are limited to 128 entries and ordinary text fields to 8,192 UTF-16 code units, with tighter limits where stated.
- JSON text inputs must parse within bounded nesting and size limits. Numeric outputs outside the safe finite range are rejected; large exact integer results use decimal strings. Indexes and half-open spans are zero-based unless a rank is explicitly described as one-based.
Alternative or Complementary methods
Use address-set arithmetic for prefix planning and a routing or interface inspection for deployed configuration. Membership and overlap do not establish reachability, ownership or route preference.
References
Similar or alternative tools
- IPv4 Wildcard Mask Pattern Check
Test arbitrary IPv4 wildcard matching where one mask bits are ignored, including noncontiguous wildcards; no firewall policy or prefix assumption.
- integer to ipv4
Convert an unsigned 32-bit integer into dotted-decimal IPv4 form.