Cisco Certified Network Associate (CCNA) Practice Exam

What is the OSPF IPv4 multicast address?

1. 224.0.0.1

2. 224.0.0.5

3. 239.255.0.1

4. 255.255.255.255

The correct answer is: 224.0.0.5

The OSPF (Open Shortest Path First) protocol uses the multicast address 224.0.0.5 for its communication. This address is specifically designated for OSPF routers to enable them to send and receive OSPF routing updates. When an OSPF router sends a hello packet, it uses the multicast address 224.0.0.5 to reach all OSPF-enabled routers on the same broadcast domain. This facilitates efficient communication, allowing OSPF routers to discover and maintain neighbor relationships. Choosing the correct multicast address is important for understanding how OSPF operates efficiently in a multi-access environment like Ethernet. Other multicast addresses mentioned do not serve this specific purpose for OSPF. For instance, 224.0.0.1 is used for all systems on a local network, while 239.255.0.1 falls under the administrative scoping for private multicast. Likewise, 255.255.255.255 is a broadcast address used to send messages to all hosts on the local network and is not specific to OSPF functionalities. Therefore, recognizing 224.0.0.5 as the multicast address for OSPF helps clarify how OSPF routers efficiently communicate and exchange routing