Cisco Certified Internetwork Expert (CCIE) Practice Test

In which type of multicast does the Cisco ASA forward IGMP messages to the upstream router?

1. Multicast group concept

2. PIM multicast routing

3. Stub multicast routing

4. Clustering

The correct answer is: Stub multicast routing

The correct answer highlights the behavior of a Cisco ASA when it comes to handling IGMP messages in a specific routing scenario. In stub multicast routing, the Cisco ASA is configured to allow IGMP messages from hosts on the local network to be forwarded to the upstream router. This is essential in enabling the communication between local multicast receivers and the upstream multicast source, ensuring that multicast traffic can reach the appropriate destinations. The stub multicast routing configuration is characterized by its simplicity; it does not involve complex routing decisions or additional multicast routers within the local network but relies on a direct path for sending IGMP membership reports and queries to the upstream router. This ensures that the ASA can maintain the state of IGMP groups and facilitate the proper delivery of multicast streams to local hosts. In contrast, the other types of multicast routing mentioned involve different roles. The multicast group concept pertains to the logic of forming groups of receivers for efficient multicast traffic distribution, while PIM multicast routing establishes protocols for inter-router multicast traffic management. Clustering generally relates to combining multiple devices to work together for load balancing and redundancy, not specifically how IGMP messages are managed. Thus, stub multicast routing is the correct context for the forwarding of IGMP messages to an upstream router by the Cisco ASA.