HP-UX IP Address and Client Management Administrator's Guide HP-UX 11i v2, HP-UX 11i v3

NOTE: Throughout this document, the terms zone and domain are used interchangeably,
though they describe different concepts. A zone describes the domain name space that a name
server has authority over. Normally, a zone does not contain any delegated subdomains, whereas
a domain can contain data delegated to other name servers. Therefore, as long as subdomains
are not delegated, a zone and a domain contain the same data.
IPv6 Support
The current support for the storage of Internet addresses in DNS is not easily extended to support
IPv6 addresses because most of the applications still assume that address queries return 32-bit
IPv4 addresses only. To support the storage of IPv6 addresses, BIND contains many types of
resource records such as AAAA. BIND also uses the ip6.arpa domain to support lookups
based on IPv6 address, instead of the ip6.int domain. However, BIND continues to support the
ip6.int domain for backward compatibility. BIND also uses the ip6.arpa domain for storing
IPv6 addresses in the DNS. The existing queries that perform additional section processing to
locate IPv4 addresses are redefined to perform additional section processing on both IPv4 and
IPv6 addresses. The existing support for IPv4 addresses is retained.
The ip6.arpa domain is a special domain defined to look up a record given an IPv6 address.
This domain provides a method to map an IPv6 address to a host name.
An IPv6 address is represented as a name in the ip6.arpa domain by a sequence of nibbles
separated by dots with the suffix .ip6.arpa. The sequence of nibbles is encoded in reverse
order wherein the low-order nibble is encoded first, followed by the next low-order nibble and
so on. Each nibble is represented by a hexadecimal digit.
For example, consider the following IPv6 address:
4321:0:1:2:3:4:567:89ab
Following is the reverse lookup domain name in the ip6.arpa domain:
b.a.9.8.7.6.5.0.4.0.0.0.3.0.0.0.2.0.0.0.1.0.0.0.0.0.0.0.1.2.3.
4.ip6.arpa.
DNS Change Notification
BIND supports DNS change notification, also known as DNS Notify, which allows master servers
to inform slave servers that new information is available. In the original DNS protocol, slave
servers (secondaries) polled the master server at an interval of time as defined in the Start of
Authority (SOA) record. At these defined intervals, the slave checked the SOA record on the
master server to find out if the serial number has changed. If it detected a change, the slave
initiated a zone transfer. The disadvantage of this approach is that slaves do not receive new
information in the interim period.
The DNS Notify operation provides a method for the master server to notify slave servers that
a zone transfer is necessary. DNS Notify uses a new DNS opcode. The notification is sent to all
the hosts listed as name servers in the name server(NS) records for the zone. Additionally, BIND
allows you list additional servers to accommodate stealth servers, which are not listed in any
name server records. You can use the zone statement to list these additional servers in the
configuration file, /etc/named.conf.
When a slave server receives the notify packet, it sends an acknowledgment. It then behaves as
if its refresh timer for that zone has expired, undergoing the same process used during expiration
time (that is, first retrieving the SOA record from the master, then initiating a zone transfer if
the record has changed).
The DNS Notify feature is enabled in the master server by default. In some environments, the
master server in a zone may be an 8.1.2 or later server with DNS Notify enabled, while the other
servers in the zone are 4.x servers (without the DNS Notify feature). In such environments,
BIND Name Service Overview 17