IPv6 Prefix Address at Offset
Select one IPv6 address at an exact zero-based offset inside a normalized prefix, including every address and avoiding 128-bit floating precision loss.
Description
Select one IPv6 address at an exact zero-based offset inside a normalized prefix, including every address and avoiding 128-bit floating precision loss.
An IPv6 prefix offset selects one address by exact displacement from its normalized network start. Decimal text keeps large offsets exact.
When to use this tool
Select one IPv6 address at an exact zero-based offset inside a normalized prefix, including every address and avoiding 128-bit floating precision loss.
- Prepare the supplied network, prefix, offset 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 network, prefix, offset. 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.address. Interpret false, null and empty lists using the distinctions below; they can be valid outputs.
Normalize network at prefix, parse offset as decimal integer text and require zero through block size minus one. Add it to the network start and return fully expanded IPv6 text.1
| Input field | Meaning and representation | Accepted input |
|---|---|---|
| network | 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 |
| prefix | prefix. | Safe integer |
| offset | Exact decimal integer text; keep it quoted in JSON rather than converting through a floating-point number. | Optional leading + or - and 1 to 256 decimal digits; no whitespace |
| Output field | Interpretation |
|---|---|
| result | Object containing the named outputs below. |
| result.address | The address value under the stated formula or text convention. |
{
"input": {
"network": "::",
"prefix": 126,
"offset": "3"
},
"output": {
"result": {
"address": "0000:0000:0000:0000:0000:0000:0000:0003"
}
}
}Limitations and assumptions
- All positions are address-set offsets, without reserved-address or usable-host filtering.
- 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
- IPv6 Prefix Address Offset
Return exact IPv6 zero-based address offset within a supplied normalized prefix, retaining null for nonmembers.
- IPv4 Address Prefix Offset
Return an address’s exact zero-based prefix offset only when it belongs to an explicitly normalized IPv4 network; outside offsets remain null.