The packets with link-local addresses as source or destination addresses are forwarded only on the local link. Link-local unicast address: used in the neighbor discovery protocol and in the communication between nodes on the local link during stateless address autoconfiguration.The meaning of each type of address is as follows: Table 1-1 Types of IPv6 unicast addresses As shown in the following figure, the subnet prefix is an IPv6 unicast address prefix which is specified when an IPv6 unicast address is configured. Syntax is required to differentiate an anycast address from a unicast address.Īs IPv6 defines, an IPv6 address with the interface identifier of all 0s is a subnet-router anycast address. They can use the format of any unicast address. A packet destined for an anycast address is transmitted to only one of the interfaces - the nearest one according to distance as defined by the routing protocol.Īpplication scenario: When a mobile host communicates with the mobile agent on the home subnet, it uses the anycast address of the subnet's routing device.Īddress specifications: Anycast addresses do not have independent address space. Anycast address: identifies a group of interfaces (which usually belong to different nodes).However, this rule does not apply to an IPv6 address with a 127-bit network prefix. A packet destined for a unicast address is transmitted to the unique interface identified by this address.Ī global unicast address cannot be the same as its network prefix, because this type of address is a subnet-router anycast address reserved for a device. Unicast address: uniquely identifies an interface and is similar to an IPv4 unicast address.IPv6 addresses are classified as unicast, anycast, and multicast addresses. "d.d.d.d" represents the low-order four groups of digits, with each "d" standing for 8 bits, which are represented by decimal digits. "X:X:X:X:X:X" represents the high-order six groups of digits, with each "X" standing for 16 bits, which are represented by hexadecimal digits. This type of IPv6 address is used to represent the addresses of IPv4 nodes. IPv4-mapped IPv6 address: The format of an IPv4-mapped IPv6 address is 0:0:0:0:0:FFFF:IPv4-address. Otherwise, when the compressed address is restored to 128 bits, the number of 0s in each segment cannot be determined. Therefore, the given example can be written as:Īn IPv6 address can contain only one double-colon substitution. Any number of consecutive groups of 0s can be replaced with two colons (::). Therefore, the preceding address can be written as: An IPv6 address example is as follows:įor convenience, leading zeros of each group can be omitted. Each "X" represents a group of hexadecimal digits. An IPv6 address in this format is written as eight groups of four hexadecimal digits (0 to 9, A to F), with each group separated by a colon (:).A 128-bit IPv6 address can be expressed in either of the following formats:
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