Which one of these statements should the designer keep in mind when considering the advanced routing features?

Which one of these statements should the designer keep in mind when considering the advanced routing features?

A.
one-way router redistribution avoids the requirement for state or default routes.

B.
Redistribution, summarization, and filtering are most often applied between the campus core and enterprise edge.

C.
Filtering only occurs on the routing domain boundary using redistribution.

D.
Summarize routes at the core toward the distribution layer.

E.
The hierarchical flexibility of IPv6 addressing avoids the requirements for routing traffic reduction using aggregation.

Explanation:

Answer A is incorrect as a default route is still required Answer B & D are incorrect as Redistribution, summarization, and filtering are used in the Distribution Layer Cisco Press CCDA 640-864 Official Certification Guide Fourth Edition, Chapter 1, Page 36 37
Answer C is incorrect as route filter can occur at either a routing domain boundary or at a routing redistribution point. Cisco Press CCDA 640-864 Official Certification Guide Fourth Edition, Chapter Answer E is correct as IPv6 allow the aggregation (summarization) of routing prefixes to reduction of the number of routes in the global routing table. Cisco Press CCDA 640-864 Official Certification Guide Fourth Edition, Chapter 9

Note: Core Layer
The core layer is the network’s high-speed switching backbone that is crucial to corporate communications. It is also referred as the backbone. The core layer should have the following characteristics:

Distribution Layer
The network’s distribution layer is the isolation point between the network’s access and core layers. The distribution layer can have many roles, including implementing the following functions:

You can use several Cisco IOS Software features to implement policy at the distribution layer:
Route Filtering
Filtering of routes can occur on either a redistribution point or in the routing domain to prevent some parts of the network from accessing other sections of the network.

Filtering at a redistribution point provides the following:

Global Aggregatable IPv6 Address
Global aggregatable unicast addresses allow the aggregation of routing prefixes. This allows a reduction of the number of routes in the global routing table. These addresses are used in links to aggregate (summarize) routes upwards to the core in large organizations or to ISPs. Global aggregatable addresses are identified by the fixed prefix of 2000:/3. As shown in Figure 9-5, the format of the global aggregatable IPv6 address is a global routing prefix starting with binary 001, followed by the subnet ID and then the 64-bit interface identifier (ID). The device MAC address is normally used as the interface ID.