Why is the summary route missing?

Refer to the exhibit.

An engineer is trying to generate a summary route in OSPF for network 10.0.0.0/8, but the summary route does not show up in the routing table .

Why is the summary route missing?
A . The summary-address command is used only for summarizing prefixes between areas.
B . The summary route is visible only in the OSPF database, not in the routing table.
C . There is no route for a subnet inside 10.0.0.0/8, so the summary route is not generated.
D . The summary route is not visible on this router, but it is visible on other OSPF routers in the same area.

View Answer

Answer: C

Explanation:

The summary-address is only used to create aggregate addresses for OSPF at an autonomous system boundary. It means this command should only be used on the ASBR when you are trying to summarize externally redistributed routes from another protocol domain or you have a NSSA area.

But a requirement to create a summarized route is:

The ASBR compares the summary route’s range of addresses with all routes redistributed into OSPF on that ASBR to find any subordinate subnets (subnets that sit inside the summary route range). If at least one subordinate subnet exists, the ASBR advertises the summary route.