Embedded IPv4 Detector¶

The Embedded IPv4 Detector is the front door for the v3.5.0 IPv6 transition tools. Paste any IPv6 literal and the detector identifies which IPv4-embedding scheme (if any) it uses, extracts the embedded IPv4 address, and offers a deep-link to the per-scheme tool drawer.

The drawer lives in the Tool Drawer on the IPv6 tab and auto-opens via the per-tool URL route /ipv6/embedded-v4.

Synopsis¶

Input	Required	Type	Notes
IPv6 address	Yes	string	Any IPv6 literal, e.g. `::ffff:192.0.2.1`

Output	Type	Notes
input	string	Echoed input
scheme	string?	One of `mapped`, `compatible`, `6to4`, `teredo`, `nat64-wkp`, `isatap`, or `null` when no embedding is detected
ipv4	string?	Extracted IPv4 dotted-quad, or `null`
deprecated	bool	`true` for `compatible` (RFC 4291 §2.5.5.1 deprecates IPv4-compatible)
detail_route	string?	Relative URL to the per-scheme tool drawer; `null` until that drawer ships
extra	object	Scheme-specific extras (e.g. Teredo flags + UDP port, 6to4 SLA ID, ISATAP u-bit)

Detection priority¶

The detector checks each scheme in order of most-specific prefix first to avoid mis-classifying an IPv4-mapped address as IPv4-compatible (both sit under ::/96):

IPv4-mapped — ::ffff:0:0/96 (RFC 4291 §2.5.5.2)
NAT64 well-known prefix — 64:ff9b::/96 (RFC 6052 §2.1)
6to4 — 2002::/16 (RFC 3056)
Teredo — 2001:0::/32 (RFC 4380)
ISATAP — IID matches *0000:5efe:V4 or *0200:5efe:V4 (RFC 5214)
IPv4-compatible (deprecated) — ::/96, excluding the reserved ::1 (loopback) and :: (unspecified) literals

If none match, the detector returns scheme: null and ipv4: null.

Examples¶

IPv4-mapped (`::ffff:0:0/96`)¶

Input:  ::ffff:192.0.2.1
Scheme: mapped
IPv4:   192.0.2.1

IPv4-compatible (DEPRECATED)¶

Input:  ::192.0.2.1
Scheme: compatible
IPv4:   192.0.2.1
Deprecated: true

RFC 4291 §2.5.5.1 deprecates this form. The detector flags it so operators auditing legacy configurations see it explicitly.

6to4 (`2002::/16`)¶

Input:  2002:c000:0201::
Scheme: 6to4
IPv4:   192.0.2.1
Extra:  sla_id (next 16 bits after the embedded V4)

Teredo (`2001:0::/32`)¶

Input:  2001:0:4136:e378:8000:63bf:3fff:fdd2
Scheme: teredo
IPv4:   <client IPv4, deobfuscated by XOR 0xFF>
Extra:  server_ipv4, flags, udp_port (deobfuscated)

NAT64 well-known prefix (`64:ff9b::/96`)¶

Input:  64:ff9b::192.0.2.1
Scheme: nat64-wkp
IPv4:   192.0.2.1

The detector currently flags only the well-known prefix. NAT64 network-specific prefixes (operator-supplied, RFC 6052 §2.2) are matched via the dedicated mapped6 tool's NAT64 prefix field.

ISATAP (`0000:5efe:V4` or `0200:5efe:V4`)¶

Input:  2001:db8::200:5efe:c000:201
Scheme: isatap
IPv4:   192.0.2.1
Extra:  globally_unique=true (u-bit set in the IID)

No embedding¶

Input:  2001:db8::1
Scheme: null

Deep-links to per-scheme tools¶

The result card includes an Open in tool button that deep-links to the per-scheme drawer when one exists. In v3.5.0 those drawers ship incrementally — when the per-scheme drawer for a given scheme has not yet shipped, the button is rendered but disabled. As subsequent v3.5.0 PRs land, each updates functions-embedded-v4.php to populate detail_route for its scheme.

REST API¶

POST /api/v1/embedded-v4 accepts a single input (string) field and returns the same scheme, ipv4, deprecated, detail_route, and extra fields documented above. See the REST API reference for the full request/response shape.

Shareable URL¶

The detector supports shareable GET URLs:

/ipv6/embedded-v4?embedded_v4_input=::ffff:192.0.2.1

This auto-opens the drawer, runs the detector, and renders the result — suitable for ticket links and runbook bookmarks.