Cisco Certified Network Associate (CCNA) Practice Exam

Which command is used to propagate a default route through OSPF v.3?

1. default-information originate

2. ospf default route

3. route propagate default

4. default-route ospf

The correct answer is: default-information originate

The command used to propagate a default route through OSPF v3 is "default-information originate." This command allows an OSPF router to advertise a default route (0.0.0.0/0) to its OSPF neighbors. This is particularly useful in larger networks where a default route can help direct traffic to an appropriate exit point, especially when routers are not aware of all routes to reach certain destinations. Using "default-information originate" enables the router to send out the default route even if it does not have an active default route configured in its routing table. In practice, this is often done by ensuring the router will announce the default route to the rest of the OSPF network, allowing other routers to recognize it as a valid path for traffic to any destination that does not have a more specific route. The other options do not accurately reflect the correct command used for this purpose. The option referring to "ospf default route" and the others are not valid OSPF commands within Cisco IOS, indicating a misunderstanding of the OSPF configuration commands. Thus, "default-information originate" stands out as the accurate command for propagating a default route through OSPF version 3.