Example 4-1 Viewing IPv6 Addresses on Windows and Mac OS Windows-OS> ipconfig Ethernet adapter Local Area Connection: Connection-specific DNS Suffix. You’ll learn more about this in Chapter 9. You may see multiple IPv6 global unicast addresses including one or more temporary addresses. The Interface ID in most cases is 64 bits. Interface ID: The Interface ID identifies the interface on the subnet, equivalent to the host portion of an IPv4 address. This makes subnetting simple and manageable. The number of bits in the Subnet ID falls between where the Global Routing Prefix ends and where the Interface ID begins. Unlike with IPv4, it is not necessary to borrow bits from the Interface ID (host portion) to create subnets. Subnet ID: The Subnet ID is a separate field for allocating subnets within the customer site. Global Routing Prefix: The Global Routing Prefix is the prefix or network portion of the address assigned by the provider, such as an ISP, to the customer site. As you can see in Figure 4-6, a GUA address is only one of several types of IPv6 unicast addresses.įigure 4-7 shows the generic structure of a GUA, which has three fields: One of the main motivations for transitioning to IPv6 is the exhaustion of its IPv4 counterpart. They play a significant role in the IPv6 addressing architecture. They are equivalent to public IPv4 addresses. Global unicast addresses (GUAs), also known as aggregatable global unicast addresses, are globally routable and reachable in the IPv6 Internet. IPv4 embedded: An IPv6 address that carries an IPv4 address in the low-order 32 bits of the address. However, unlike RFC 1918 addresses, these addresses are not intended to be statefully translated to a global unicast address. Unique local: Similar to a private address in IPv4 (RFC 1918) and not intended to be routable in the IPv6 Internet. Unspecified address: Used only as a source address and indicates the absence of an IPv6 address. Loopback: An address not assigned to any physical interface that can be used for a host to send an IPv6 packet to itself. Link-local: Used only to communicate with devices on the same local link (covered in more detail in Chapter 6). Global unicast: A routable address in the IPv6 Internet, similar to a public IPv4 address (covered in more detail in Chapter 5). The following is a quick preview of each type of unicast address discussed in this section: This section covers the different types of unicast addresses, as illustrated in Figure 4-6. Remember that IPv6 does not include a broadcast address. Notice that there is no broadcast address shown in Figure 4-6.
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