Cisco Certified Network Associate (CCNA) Practice Exam

Which criteria is NOT required for OSPF routers to form a neighborship?

1. Matching authentication passwords

2. Different router IDs

3. Matching area ID

4. Matching hello interval

The correct answer is: Matching hello interval

For OSPF (Open Shortest Path First) routers to successfully form a neighborship, several criteria must be met. Among these, matching the hello interval is not strictly required, which is why the selected answer is appropriate. When OSPF routers attempt to establish a neighborship, they primarily look for matching values for several key parameters to ensure compatibility. These parameters include the area ID, which needs to be the same for routers to communicate effectively within that specific area. Additionally, matching authentication passwords is critical for security purposes, as it prevents unauthorized routers from establishing connections. Router IDs, while essential for OSPF operation, do not have to match between the routers forming the neighborship. Each router must have a unique router ID, meaning that the router IDs should be different for each router to avoid conflicts. The hello interval, on the other hand, is the time interval at which OSPF routers send hello packets to discover neighbors. While having the same hello interval can facilitate quicker and more stable neighbor relationships, it is not a strict requirement for forming those relationships. If the hello intervals differ, OSPF will still initiate the neighborship, but it may lead to issues in neighbor maintenance or costs in terms of responsiveness