[#INTERNAL_IN_IPV6_PREFIX]
= INTERNAL_IN_IPV6_PREFIX
:mrdocs:

Prefix of an IPv6 address when it contains an embedded "internal" address. Used when (un)serializing addresses in ADDRv1 format (pre‐BIP155). The prefix comes from 0xFD + SHA256("bitcoin")[0:5]. Such dummy IPv6 addresses are guaranteed to not be publicly routable as they fall under RFC4193's fc00::/7 subnet allocated to unique‐local addresses.

== Synopsis

Declared in `<netaddress.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
inline constexpr std::array<uint8_t, 6> INTERNAL_IN_IPV6_PREFIX = {
    0xFD, 0x6B, 0x88, 0xC0, 0x87, 0x24 // 0xFD + sha256("bitcoin")[0:5].
};
----


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