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:
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 maskUse the following commands to configure RTA for external router summarization as shown in the
Figure.
RTA(config)#router ospf 1RTA(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 1RTB(config-router)#area 1 range 192.168.16.0 255.255.252.0
Notice that the area 1 rangecommand in this example specifies the area containing the range to
be summarized before being injected into Area 0.