H3C Technologies H3C S12500 Series Switches - Manual (Page 117)

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Address autoconfiguration
To simplify host configuration, IPv6 supports stateful and stateless address autoconfiguration.
• Stateful address autoconfiguration enables a host to acquire an IPv6 address and other
configuration information from a server (for example, a DHCPv6 server). For more information
about DHCPv6 server, see "Configuring DHCPv6 server."
• Stateless address autoconfiguration enables a host to automatically generate an IPv6 address and
other configuration information by using its link-layer address and the prefix information advertised
by a router.
To communicate with other hosts on the same link, a host automatically generates a link-local address
based on its link-layer address and the link-local address prefix (FE80::/10).
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Built-in security
IPv6 defines extension headers to support IPsec. IPsec provides end-to-end security and enhances
interoperability among different IPv6 applications.
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QoS support
The Flow Label field in the IPv6 header allows the device to label the packets of a specific flow for special
handling.
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Enhanced neighbor discovery mechanism
The IPv6 neighbor discovery protocol uses a group of ICMPv6 messages to manage information
exchange among neighboring nodes on the same link. The group of ICMPv6 messages replaces ARP
messages, ICMPv4 Router Discovery messages, and ICMPv4 Redirect messages and provides a series of
other functions.
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Flexible extension headers
IPv6 eliminates the Options field in the header and introduces optional extension headers to provide
scalability and improve efficiency. The Options field in the IPv4 packet header contains up to 40 bytes,
whereas the IPv6 extension headers are restricted to the maximum size of IPv6 packets.
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IPv6 addresses
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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 two 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.
IMPORTANT:
A double colon can appear once or not at all in an IPv6 address. This limit allows the device to determine
how many zeros the double colon represents and correctly convert it to zeros to restore a 128-bit IPv6
address.