Bind 9 Administrator Reference Manual

Chapter 4. Advanced Concepts
ns0 14400 IN A6 0 3ffe:8050:201:1860:42::1
ns1 14400 IN A 192.168.42.1
It is recommended that IPv4-in-IPv6 mapped addresses not be used. If a host has an IPv4 address, use an
A record, not an A6, with ::ffff:192.168.42.1 as the address.
4.8.3. Address to Name Lookups Using Nibble Format
While the use of nibble format to look up names is deprecated, it is supported for backwards
compatiblity with existing IPv6 applications.
When looking up an address in nibble format, the address components are simply reversed, just as in
IPv4, and ip6.int. is appended to the resulting name. For example, the following would provide
reverse name lookup for a host with address 3ffe:8050:201:1860:42::1.
$ORIGIN 0.6.8.1.1.0.2.0.0.5.0.8.e.f.f.3.ip6.int.
1.0.0.0.0.0.0.0.0.0.0.0.2.4.0.0 14400 IN PTR host.example.com.
4.8.4. Address to Name Lookups Using Bitstring Format
Bitstring labels can start and end on any bit boundary, rather than on a multiple of 4 bits as in the nibble
format. They also use ip6.arpa rather than ip6.int.
To replicate the previous example using bitstrings:
$ORIGIN \[x3ffe805002011860/64].ip6.arpa.
\[x0042000000000001/64] 14400 IN PTR host.example.com.
4.8.5. Using DNAME for Delegation of IPv6 Reverse Addresses
In IPV6, the same host may have many addresses from many network providers. Since the trailing
portion of the address usually remains constant, DNAME can help reduce the number of zone files used
for reverse mapping that need to be maintained.
For example, consider a host which has two providers (example.net and example2.net) and
therefore two IPv6 addresses. Since the host chooses its own 64 bit host address portion, the provider
address is the only part that changes:
$ORIGIN example.com.
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