Section: Addressing and Routing Protocols in an Existing Network Explanation

The global unicast IP version 6 (IPv6) address space contains an inherent hierarchy that simplifies Internet routing tables. A global unicast address, which is also referred to as an aggregatable global address, is designed to minimize the size of Internet routing tables. A global unicast address contains three distinct parts:

The Global Routing Prefix is a 48bit field that is defined by the Internet service provider (ISP). The SLA is a 16bit field that identifies a site and is analogous to a subnet in IPv4. The Interface ID is a 64bit field that must be globally unique? therefore, it typically contains the Media Access Control (MAC) address of the originating device in extended universal identifier (EUI)64 format. Because there is an inherent hierarchy in the aggregatable global address scheme, these addresses lend themselves to simple consolidation, which greatly reduces the complexity of Internet routing tables.

Anycast addresses are used to send packets to the closest device that is configured with the anycast address. Therefore, an anycast address can be described as a one-to-nearest address. The closest device is selected by the routing protocol that is used by the router. Because anycast addresses use the same address for multiple devices in a group, anycast addresses are ideal for load balancing.

Link-local addresses are unicast addresses used for communication over a single link. Routers do not forward traffic sent to a link-local address? the traffic stays on the local link. These addresses always begin with FE8, FE9, FEA, or FEB. Because link-local addresses are used to form neighbor adjacencies, they should always be considered when creating access control lists (ACLs) to filter traffic. If the ACL explicitly denies the relevant link-local addresses on a router, neighbor relationships can fail after an ACL is applied to an interface.

IPv6 does not use broadcast addresses. A broadcast address is an IPv4 address that is used to communicate with all devices in a broadcast domain at once.

Reference: CCDA 200-310 Official Cert Guide, Chapter 9, Global Unicast Addresses, p. 342 Cisco: IPv6 Configuration Guide, Cisco IOS Release 15.2S: Aggregatable Global Address

Which of the following IPv6 address spaces contains an inherent hierarchy that simplifies Internet routing tables?

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