Cisco Certified Network Associate (CCNA) Practice Exam

What does the marker O*IA indicate in OSPF routing?

1. External route

2. Summary route

3. Internal route

4. NSSA route

The correct answer is: Summary route

The marker O*IA in OSPF routing indicates an external route that has been redistributed into OSPF from another routing protocol and is located in a stub area. The 'O' signifies that it is an OSPF-learned route. The asterisk (*) denotes that it is an external route, while the "IA" stands for Inter-Area, meaning it is an external route learned from another OSPF area. In this context, external routes are associated with routes that are added to OSPF from other protocols or from static routes, allowing OSPF to leverage information from outside its own domain. The specific designation of "IA" in this case indicates the route is an inter-area route and is part of the special handling that occurs in stub areas, ensuring that information from external sources can still be propagated throughout the OSPF domain. Understanding the role of these markers is crucial for network engineers working with OSPF, as it helps interpret the routing table effectively, especially in environments with multiple routing protocols or complex topologies.