Cisco Certified Network Associate (CCNA) Practice Exam

When configuring networks to be advertised via OSPF, what type of mask is used?

1. Subnet mask

2. Wildcard mask

3. Default mask

4. CIDR mask

The correct answer is: Wildcard mask

The correct answer is the wildcard mask, which is used in OSPF (Open Shortest Path First) configuration to specify which addresses should be considered for inclusion in OSPF routing. Wildcard masks work differently than subnet masks; they indicate which bits of an IP address should be matched and which bits can be ignored. In the context of OSPF, this allows for more flexible network summarization and filtering when defining the networks that will participate in OSPF. When configuring OSPF, a wildcard mask is often applied to the network command. For instance, if you want to identify all hosts in the 192.168.1.0 network, a wildcard mask of 0.0.0.255 would ignore the last octet, thereby including all hosts from 192.168.1.0 to 192.168.1.255. This is crucial for efficient routing and ensuring that the desired networks are properly shared among OSPF routers. Subnet masks, while important in IP addressing, are not used directly in OSPF configuration commands. Default masks may refer to a standard classful addressing approach, but they do not provide the flexibility needed for dynamic routing protocols. CIDR (Classless Inter-Domain