Refer to the exhibit. What method can be used to enable an OSPF router to advertise a default route to neighboring OSPF routers?

To enable an OSPF router to advertise a default route to neighboring OSPF routers, the method used is:

• Use the default-information originate command on R0-A.

This command is used on the OSPF router that has a connection to an external network (such as an ISP) to generate a default route into the OSPF domain. If R0-A has the connection to the ISP, then it would be the router to originate the default route to the other OSPF routers.

Here’s why the other options are less suitable:

1. Use a static route pointing to the ISP and redistribute it: While redistributing a static default route into OSPF is a valid method, the option is incomplete because it doesn’t specify where to apply the redistribution. Redistribution would typically be done on the router connected to the ISP, in this case, R0-A.
2. Use the default-information originate command on ISP: This command should be used on the OSPF router within your network that you want to advertise the default route, not on the ISP’s router.
3. Use the redistribute static command on R0-A: Redistributing static routes is also a method to propagate default routes in OSPF, but this option is not specifying which static route to redistribute. To properly redistribute a default route, there should be a static default route configured on R0-A that is then redistributed into OSPF.
4. Use the redistribute static command on ISP: The ISP router is typically not under your administrative control, and even if it were, you would not generally redistribute routes from the ISP into your OSPF process; rather, you would generate a default route from your edge router using the default-information originate command.

Therefore, the correct method to advertise a default route to neighboring OSPF routers is to use the default-information originate command on R0-A, assuming it has the direct connection to the ISP.