Question 1mediummatching
Full question →Match each OSPF adjacency requirement or concept to its most accurate description.
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mediummatchingObjective-mapped
Match each OSPF adjacency requirement or concept to its most accurate description.
Common exam trap
Common exam trap: answer the scenario, not the keyword
A common exam trap with OSPF adjacency questions is confusing the router ID with the OSPF process ID. The router ID uniquely identifies the router within the OSPF domain and must be consistent for neighbor relationships, but it is not the same as the local process ID configured on the router. Another trap is assuming that mismatched hello and dead timers or area IDs will still allow adjacency formation; in reality, these parameters must match exactly on both routers to establish adjacency. Misunderstanding these requirements leads to incorrect answers about why OSPF neighbors fail to form.
Technical deep dive
How to think about this question
OSPF adjacency formation is a fundamental concept in Cisco routing that ensures routers can exchange routing information reliably. The process begins with routers sending Hello packets to discover neighbors on a shared network segment. For two routers to become OSPF neighbors, they must agree on several key parameters, including the hello interval, dead interval, area ID, and network type. These parameters ensure that routers have compatible settings and can maintain stable communication. The router ID uniquely identifies each router in the OSPF domain but does not need to match between neighbors. The decision process for establishing OSPF adjacency involves comparing the hello and dead timers first; if these timers do not match, routers will not recognize each other as neighbors. Next, routers verify that they are in the same OSPF area by matching the area ID on the interface. Network type compatibility is also checked because different network types (broadcast, point-to-point, NBMA) have different adjacency behaviors. Only after these parameters align will routers proceed to exchange database description packets and synchronize their link-state databases. A frequent exam trap is confusing the router ID with the OSPF process ID or assuming that mismatched timers or area IDs can still allow adjacency. In practice, mismatched hello or dead timers cause routers to ignore each other's Hello packets, preventing neighbor formation. Similarly, routers in different areas will not form adjacencies even if other parameters match. Understanding these nuances helps avoid mistakes and ensures correct interpretation of OSPF adjacency requirements on the CCNA exam.
KKey Concepts to Remember
- OSPF routers must match hello and dead timers exactly on shared interfaces to successfully form neighbor adjacencies.
- The OSPF area ID must be identical on both routers' interfaces to establish adjacency within the same OSPF area.
- OSPF router ID uniquely identifies each router but does not need to match between neighbors for adjacency formation.
- Network type compatibility (broadcast, point-to-point, NBMA) influences OSPF adjacency behavior and must be consistent between neighbors.
- Mismatched hello or dead timers cause routers to ignore each other's Hello packets, preventing neighbor relationships.
- OSPF adjacency formation proceeds only after routers verify matching timers, area IDs, and compatible network types.
- The OSPF process ID is a local router configuration and does not affect neighbor adjacency or router ID selection.
- Routers exchange database description packets only after successfully establishing neighbor adjacency through parameter matching.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
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More questions from this exam
Keep practising from the same exam bank, or move into a focused topic page if this question exposed a weak area.
Question 1
A router learns the same prefix from both OSPF and EIGRP. Which route is installed by default?
Question 2
A router shows this output: R1#show ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 10.1.1.2 1 FULL/DR 00:00:34 192.168.12.2 GigabitEthernet0/0 10.1.1.3 1 2WAY/DROTHER 00:00:39 192.168.12.3 GigabitEthernet0/0 Which statement is correct?
Question 3
What is the OSPF metric called?
Question 4
A non-root switch has two uplinks toward the root bridge. One path has a lower total STP cost than the other. What role will the lower-cost uplink have?
Question 5
A router interface applies this ACL inbound: 10 deny tcp any any eq 80 20 permit ip any any A user reports that web browsing to a server by IP address fails, but ping works. Which statement best explains the behavior?
Question 6
A router learns route 198.51.100.0/24 from OSPF with AD 110 and also has a static route to the same prefix configured with AD 150. Which route is installed?
FAQ
Questions learners often ask
What does this 200-301 question test?
OSPF routers must match hello and dead timers exactly on shared interfaces to successfully form neighbor adjacencies.
What exam trap should I watch out for?
Common exam trap: answer the scenario, not the keyword: A common exam trap with OSPF adjacency questions is confusing the router ID with the OSPF process ID. The router ID uniquely identifies the router within the OSPF domain and must be consistent for neighbor relationships, but it is not the same as the local process ID configured on the router. Another trap is assuming that mismatched hello and dead timers or area IDs will still allow adjacency formation; in reality, these parameters must match exactly on both routers to establish adjacency. Misunderstanding these requirements leads to incorrect answers about why OSPF neighbors fail to form.
What should I do if I get this 200-301 question wrong?
Then try more questions from the same exam bank and focus on understanding why the wrong options are tempting.
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