Refer to the exhibit.

The network associate is configuring OSPF on the Core router. All the connections to the branches
should be participating in OSPF. The link to the ISP should NOT participate in OSPF and should only
be advertised as the default route. What set of commands will properly configure the Core router?

A.
Core(config-router)# default-information originate Core(config-router)# network 10.0.0.0
0.255.255.255 area 0 Core(config-router)# exit Core(config)# ip route 0.0.0.0 0.0.0.0 10.10.2.14

B.
Core(config-router)# default-information originate Core(config-router)# network 10.10.2.13
0.0.0.242 area 0 Core(config-router)# exit Core(config)# ip route 0.0.0.0 0.0.0.0 10.10.2.14

C.
Core(config-router)# default-information originate Core(config-router)# network 10.10.2.16
0.0.0.15 area 0 Core(config-router)# exit Core(config)# ip route 0.0.0.0 0.0.0.0 10.10.2.14

D.
Core(config-router)# default-information originate Core(config-router)# network 10.10.2.32
0.0.0.31 area 0 Core(config-router)# exit Core(config)# ip route 0.0.0.0 0.0.0.0 10.10.2.14

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 theexisting 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 (defaultinformation 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.
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