IPv6 address offset

ipv6-address-offset · version 1.0.0 · URLs & IP addresses · free, no key needed

Add a signed integer offset to an IPv6 address, throwing if the result leaves the IPv6 address space.

Use when you need to: ipv6 address offset · add offset to ipv6 address · ipv6 address increment.

Supported

• ipv6 address offset
• add offset to ipv6 address
• ipv6 address increment

Not supported

• IPv4
• CIDR-bounded wraparound

Behavior

• address accepts any RFC 4291 textual form (see ipv6-parse); offset is a canonical signed decimal integer string (may be negative or zero) since it may exceed the safe JSON number range.
• result is address's 128-bit value plus offset, formatted as the RFC 5952 canonical address.
• Throws if the result falls outside 0..340282366920938463463374607431768211455 (::..ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff).

Input

• address (string, required): max length 45
• offset (string, required): max length 40; pattern ^-?(0|[1-9][0-9]*)$

Output

• result (string, required): max length 45

Limits

• max address length: 45
• offset max abs: 340282366920938463463374607431768211455

Example

Request input:

{
  "address": "2001:db8::1",
  "offset": "10"
}

Response:

{
  "result": {
    "result": "2001:db8::b"
  }
}

How to call it

MCP

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

{
  "id": "ipv6-address-offset",
  "version": "1.0.0",
  "input": {
    "address": "2001:db8::1",
    "offset": "10"
  }
}

HTTP (no key)

curl -X POST https://computefirst.net/v1/tools/ipv6-address-offset/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"address":"2001:db8::1","offset":"10"}'

The machine-readable contract is at /v1/tools/ipv6-address-offset/versions/1.0.0.

CLI

node cli.mjs run ipv6-address-offset 1.0.0 --input input.json --base-url https://computefirst.net

Get the client at /clients/cli/.

Related tools

• IPv4 address offset: Add a signed integer offset to an IPv4 address, throwing if the result leaves the IPv4 address space.
• IPv6 parse: Parse an IPv6 address (any RFC 4291 textual form) into its 8 hextets and a 128-bit integer string.
• IPv6 range to cidrs: Convert an arbitrary IPv6 address range into the minimal list of CIDR blocks that exactly covers it.
• IPv4 range to cidrs: Convert an arbitrary IPv4 address range into the minimal list of CIDR blocks that exactly covers it.
• IPv6 address classify: Classify an IPv6 address against the static IANA IPv6 special-purpose address registry.
• IPv6 address compare: Compare two IPv6 addresses by their numeric 128-bit value.