Refer to the exhibit.

What must be configured on router RTA to summarize all routes from area 0 to area 1?

A.
area 0 range 172.16.96.0 255.255.224.0

B.
area 0 range 172.16.96.0 255.255.255.0

C.
area 1 range 172.16.96.0 255.255.224.0

D.
area 1 range 172.16.96.0 255.255.0.0

E.
summary-address 172.16.96.0 255.255.224.0

F.
summary-address 172.16.96.0 0.0.63.255

Explanation:
Recall that summarization is the consolidation of multiple routes into one single, supernet
advertisement. See Module 2 for more details on this. Proper summarization requires
contiguous, sequential, addressing. 200.10.0.0, 200.10.1.0, 200.10.2.0, and so on are
examples of contiguous addressing. OSPF routers can be manually configured to advertise
a supernet route, which is different from an LSA summary route.
Route summarization directly affects the amount of bandwidth, CPU, and memory resources
that are consumed by the OSPF process. With summarization, if a network link fails or flaps,
the topology change will not be propagated into the backbone, and other areas by way of the
backbone. As discussed in previous modules, route summarization protects routers from
needless routing table recalculations. Because the SPF calculation places a significant
demand on a router CPU, proper summarization is an important part of OSPF configuration.
OSPF supports the following two types of summarization:
Interarea route summarization – Interarea route summarization is done on ABRs and applies
to routes from within each area. It does not apply to external routes injected into OSPF by
way of redistribution. To take advantage of summarization, network numbers within areas
should be contiguous.
External route summarization – External route summarization is specific to external routes
that are injected into OSPF by way of redistribution. Here again, it is important to ensure that
external address ranges that are being summarized are contiguous. Summarization of
overlapping ranges from two different routers could cause packets to be sent to the wrong
destination. Only ASBRs can summarize external routes.

To configure an ABR to summarize routes for a specific area before injecting them into a
different area, use the following syntax:
Router(config-router)#area area-id range address mask
To configure an ASBR to summarize external routes before injecting them into the OSPF
domain, use the following syntax:
Router(config-router)#summary-address address mask
Use the following commands to configure RTA for external router summarization as shown
in the Figure.
RTA(config)#router ospf 1
RTA(config-router)#summary-address 200.9.0.0 255.255.0.0
Once configured, RTA will send only a single summary route, 200.9.0.0/16, into the OSPF
domain.
Because RTB sits on the border between Area 0 and Area 1, it should be configured to
perform interarea summarization, shown as follows:
RTB(config)#router ospf 1
RTB(config-router)#area 1 range 192.168.16.0 255.255.252.0
Notice that the area 1 range command in this example specifies the area containing the
range to be summarized before being injected into Area 0.