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MAC → IPv6 Derivation

The MAC-derivation tool is in the Tool Drawer on the IPv6 tab. Enter a 48-bit MAC address and the tool returns the three IPv6 forms generated from it: the modified EUI-64 interface identifier, the link-local address, and the solicited-node multicast address.

What it does

Given any 48-bit MAC, the tool computes (per RFC 4291 §2.5.1 and §2.7.1):

  • Modified EUI-64 interface ID — the 64-bit identifier formed by flipping the U/L (universal/local) bit in the first MAC byte and inserting the 16-bit value 0xFFFE between the OUI and NIC halves.
  • Link-local address — fe80:: concatenated with the EUI-64 interface identifier, then canonicalised through inet_ntop() so the output is always lowercase and maximally compressed.
  • Solicited-node multicast address — ff02::1:ff followed by the low 24 bits of the unicast address. IPv6 Neighbor Discovery uses these multicast groups so a host only listens for resolution requests targeted at its own address.

Accepted input formats

The tool accepts any of the four common MAC notations:

Notation Example
Colon-separated 00:24:b9:7e:ab:cd
Hyphen 00-24-b9-7e-ab-cd
Cisco dotted 0024.b97e.abcd
Bare hex 0024b97eabcd

Input is case-insensitive. The result block always shows the MAC canonicalised to lower-case colon-separated form.

Worked example

Input MAC 00:24:b9:7e:ab:cd:

Step Value
1. First byte 0x00 XOR 0x02 (U/L flip) 0x02
2. Insert ff:fe between OUI and NIC 02:24:b9:ff:fe:7e:ab:cd
3. Group as four hextets 0224:b9ff:fe7e:abcd (EUI-64)
4. Prepend fe80:: fe80::224:b9ff:fe7e:abcd (link-local)
5. Take low 24 bits → 7e:ab:cd ff02::1:ff7e:abcd (solicited-node)

Multicast warning

If the input MAC has the I/G (multicast) bit set in the first byte — for example 01:00:5e:00:00:01 — the tool still returns derived values, but it raises a yellow warning band. Multicast MACs are not valid host identifiers; the math still works, but the resulting interface ID would never be assigned to a real interface.

Shareable URL

The tool supports the standard shareable-URL pattern. The colon separators must be URL-encoded as %3A:

/ipv6/derive?derive_mac=00%3A24%3Ab9%3A7e%3Aab%3Acd

The drawer auto-opens and all four rows hydrate from the URL.

REST API

POST /api/v1/derive

Request body:

{
  "mac": "00:24:b9:7e:ab:cd"
}

Successful response (HTTP 200):

{
  "ok": true,
  "data": {
    "mac_canonical":  "00:24:b9:7e:ab:cd",
    "eui64":          "0224:b9ff:fe7e:abcd",
    "ul_bit_flipped": true,
    "link_local":     "fe80::224:b9ff:fe7e:abcd",
    "solicited_node": "ff02::1:ff7e:abcd",
    "warning":        null
  }
}

curl example:

curl -s -X POST https://your-host/api/v1/derive \
  -H 'Content-Type: application/json' \
  -d '{"mac":"00:24:b9:7e:ab:cd"}'

Warning case (multicast bit set on the input MAC) — HTTP 200, but warning is a non-null string:

{
  "ok": true,
  "data": {
    "mac_canonical":  "01:00:5e:00:00:01",
    "eui64":          "0300:5eff:fe00:0001",
    "ul_bit_flipped": true,
    "link_local":     "fe80::300:5eff:fe00:1",
    "solicited_node": "ff02::1:ff00:1",
    "warning":        "Multicast bit set on input MAC; derived addresses are still computed but the source MAC is not a valid unicast hardware address."
  }
}

Error case (malformed MAC) — HTTP 400:

{
  "ok": false,
  "error": "Invalid MAC address: not-a-mac"
}

See the full API reference at POST /api/v1/derive.