Configure Interface IPv6 Address

The most striking difference between IPv6 and IPv4 is that the length of the IP address increases from 32 bits to 128 bits. The IPv6 address is represented as a series of 16-bit hex numbers separated by colon (:). Each IPv6 address is divided into eight groups, each group of 16 bits represented by four hexadecimal digits, and the groups are separated by colons, such as 2000:0000:240F:0000:0000:0CB0:123A:15AB.

In order to simplify the representation of the IPv6 address, process the “0” in the IPV6 address as follows:

• The preamble “0” in each group can be omitted, that is, the above address can be represented as 2000:0:240F:0:0:CB0:123A:15AB.
• If the address contains two or more consecutive groups of zero, it can be replaced by a double colon "::" that is, the above address can be represented as 2000:0:240F:: CB0:123A:15AB.
• The double colon "::" can only be used once in an IPv6 address. Otherwise, the number of zeros represented by "::" cannot be determined when the device converts "::" to zero to recover 128-bit addresses.

The IPv6 address consists of two parts: address prefix and interface identifier. The address prefix is equivalent to the network number field in the IPv4 address and the interface identifier is equivalent to the host number field in the IPv4 address.

The IPv6 address prefix is expressed as: IPv6 address/prefix length. The IPv6 address is any of the forms listed above, and the prefix length is a decimal number that indicates how many bits in front of the IPv6 address is the address prefix.

There are three kinds of IPv6 addresses, that is, unicast address, multicast address, and anycast address:

• Unicast address: used to uniquely identify an interface, similar to IPv4 unicast address. The packets sent to one unicast address will be sent to the interface identified by this address.
• Multicast address: used to identify a set of interfaces, similar to IPv4 multicast address. The packets sent to one multicast address are sent to all the interfaces identified by this address.
• Anycast Address: used to identify a group of interfaces and the packet whose destination is an anycast address is sent only to one interface in the group. According to the routing protocol, the interface of receiving the packet is the closest interface from source.

The IPv6 address type is specified by the first few bits of the address, called the format prefix. The corresponding relationship between the main address type and the format prefix is shown in Table 1-2.

Table 5-2 The corresponding relationship between the IPv6 address type and the format prefix

IPv6 unicast addresses can be of various types, including global unicast addresses, link local addresses, and site local addresses.

• The global unicast address is equivalent to the IPv4 public network address, which is provided to the Internet service provider. This type of addresses allows the aggregation of routing prefixes, thus limiting the number of global routing entries.
• Link local addresses are used for the communication between the local nodes on the link in the neighborhood discovery protocol and stateless automatic configuration. The packet using the link local address as the source or destination address is not forwarded to other links.
• The local address of the site is similar to the private address in IPv4. The packet using the local address of the site as the source or destination address is not forwarded to other sites outside the site.
• Loopback address: Unicast address 0:0:0:0:0:0:0:0:0:1 (simplified as: 1) is called a loopback address and cannot be assigned to any physical interface. Its function is the same as the loopback address in IPv4, that is, the node sends IPv6 packets to itself.
• Un-specified address: The address “::”is called an unspecified address and cannot be assigned to any node. Before a node obtains a valid IPv6 address, it can be entered in the source address field of the IPv6 packet sent, but not as the destination address of the IPv6 packet.

The special multicast addresses reserved by IPv6 are shown in table 1-3.

Table 5-3 The special multicast address list of IPv6

Configuration Condition

None

Configure the IPv6 Address of the Interface

Table 5-4 Configure the IPv6 address of the interface

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  One interface can be configured with multiple IPv6 addresses.
• After one interface is configured with the IPv6 address, automatically enable the IPv6 function.

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