Explanation/Reference:
Explanation:
There are two ways to inject a default route into a normal area.1. If the ASBR already has the default route
in its routing table, you can advertise the existing 0.0.0.0/0 into the OSPF domain with the default-
information originate router configuration command.2. If the ASBR doesn't have a default route, you can
add the keyword always to the default-information originate command (default-information originate
always). This command will advertise a default route into the OSPF domain, regardless of whether it has a
route to 0.0.0.0. Another benefit of adding always keyword is that it can add stability to the internetwork.
For example, if the ASBR is learning a default route from another routing domain such as RIP and this
route is flapping, then without the always keyword, each time the route flaps, the ASBR will send a new
Type 5 LSA into the OSPF domain causing some instability inside the OSPF domain. With the always
keyword, the ASBR will advertise the default inside the OSPF domain always, In the example shown here,
only choice C is correct as the wildcard mask correctly specifies the 10.10.2.16 0.0.0.15 networks, which
include all IP addresses in the 10.10.2.16-10.10.2.31 range. In this question we were told that the ISP link
should NOT be configured for OSPF, making choice A incorrect.
Reference:
http://www.cisco.com/en/US/tech/tk365/technologies_configuration_example09186a00801ec9f0.shtml