The IPv6 Address Types and Prefix Length

The IPv6 Address Types

There are three basic IPv6 address types:

Unicast – A unicast address is the most common form of an IP address and  we can also assign this to one network interface. We have also learnt about IPv4 unicast addresses in the previous lessons.  An IPv6 unicast address uniquely identifies an interface on an IPv6-enabled device. For communication over IPv6, source IPv6 address must be a unicast address.  IPv6 unicast have five different types: global unicast addresses, link-local addresses, site-local addresses, unique local IPv6 unicast addresses, and special addresses. We will discuss these addresses briefly in later articles.

Multicast– We also learnt multicast addresses and the range of multicast addresses in IPv4 addresses. The multicast addresses identify multiple network interfaces/hosts. Using IPv6 multicast address we can also send a single IPv6 packet to multiple destinations.

Anycast– An IPv6 anycast address is any IPv6 unicast address. We can assign this address to multiple network devices. Like a multicast address,  anycast address identifies multiple interfaces; however, while multicast packets accepted by multiple machines, anycast packets delivered to the nearest device having that address.

Note – Broadcast addresses are no longer exist in IPv6. However, there is an IPv6 all-nodes multicast address that essentially gives the same result.

IPv6 Prefix Length

Remember the network portion or the prefix of an IPv4 address. We can identify the network with dotted-decimal subnet mask or slash notation. For example, an IPv4 address of 172.16.16.100 with dotted-decimal subnet mask 255.255.0.0 is equivalent to 172.16.16.0/16.

IPv6 address uses the prefix length to represent the prefix portion. The IPv6 address does not use the dotted-decimal subnet mask notation. The length of the prefix is used to specify the network portion of an IPv6 address using the IPv6 address/prefix length. The range of prefix is from 0 to 128. The typical prefix length for the most network is /64. This means the network portion or prefix of the address is 64 bit long and other the host portion is also 64 bit. The figure illustrates the prefix of IPv6 address.

IPv6 address types and prefix

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