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A DDNS policy contains the DDNS server address, login ID, password, associated SSL client policy,
and update time interval. After creating a DDNS policy, you can apply it to multiple interfaces to
simplify DDNS configuration.
DDNS is supported by only IPv4 DNS, and it is used to update the mappings between domain names
and IPv4 addresses.
IPv6
IPv6, also called IP next generation (IPng), was designed by the IETF as the successor to IPv4. One
significant difference between IPv6 and IPv4 is that IPv6 increases the IP address size from 32 bits
to 128 bits.
IPv6 address formats
An IPv6 address is represented as a set of 16-bit hexadecimals separated by colons (:). An IPv6
address is divided into eight groups, and each 16-bit group is represented by four hexadecimal
numbers, for example, 2001:0000:130F:0000:0000:09C0:876A:130B.
To simplify the representation of IPv6 addresses, you can handle zeros in IPv6 addresses by using
the following methods:
•
The leading zeros in each group can be removed. For example, the above address can be
represented in a shorter format as 2001:0:130F:0:0:9C0:876A:130B.
•
If an IPv6 address contains one or more consecutive groups of zeros, they can be replaced by
a double colon (::). For example, the above address can be represented in the shortest format
as 2001:0:130F::9C0:876A:130B.
An IPv6 address consists of an address prefix and an interface ID, which are equivalent to the
network ID and the host ID of an IPv4 address.
An IPv6 address prefix is written in IPv6-address/prefix-length notation. The prefix-length is a
decimal number indicating how many leftmost bits of the IPv6 address are in the address prefix.
IPv6 address types
IPv6 addresses include the following types:
•
Unicast
address
—An identifier for a single interface, similar to an IPv4 unicast address. A
packet sent to a unicast address is delivered to the interface identified by that address.
•
Multicast
address
—An identifier for a set of interfaces (typically belonging to different nodes),
similar to an IPv4 multicast address. A packet sent to a multicast address is delivered to all
interfaces identified by that address.
•
Broadcast addresses are replaced by multicast addresses in IPv6.
•
Anycast
address
—An identifier for a set of interfaces (typically belonging to different nodes). A
packet sent to an anycast address is delivered to the nearest interface among the interfaces
identified by that address. The nearest interface is chosen according to the routing protocol's
measure of distance.
The type of an IPv6 address is designated by the first several bits, called the format prefix. The
following table shows mappings between address types and format prefixes:
