The NAT64 prefixes that addresses reveal, when they are the IPv6
addresses a resolver gave for ipv4only.arpa (RFC 7050). That name has
two addresses, both IPv4: 192.0.0.170 and 192.0.0.171. An IPv6 answer was
therefore made by a DNS64 resolver, from the network's NAT64 prefix, and
the place of one of those two addresses in it gives the prefix and its
length. Byte 8 must be zero where the format reserves it (every length but
96), so bytes that only happen to spell one of the two addresses around a
non-zero byte 8 name no prefix. Text that is not an IPv6 address is passed
over.
The NAT64 prefixes that
addressesreveal, when they are the IPv6 addresses a resolver gave foripv4only.arpa(RFC 7050). That name has two addresses, both IPv4: 192.0.0.170 and 192.0.0.171. An IPv6 answer was therefore made by a DNS64 resolver, from the network's NAT64 prefix, and the place of one of those two addresses in it gives the prefix and its length. Byte 8 must be zero where the format reserves it (every length but 96), so bytes that only happen to spell one of the two addresses around a non-zero byte 8 name no prefix. Text that is not an IPv6 address is passed over.