The correct answer is that the 2WAY/DROTHER state is normal behavior on a broadcast segment. On a multi-access Ethernet network, OSPF elects a Designated Router (DR) and Backup Designated Router (BDR) to reduce adjacencies and link-state flooding. All other routers, known as DROTHERs, form full adjacencies only with the DR and BDR, while they remain in the 2WAY state with each other—this is by design, not a fault. For the CCNA 200-301 v2 exam, this question tests your understanding of OSPF network types and neighbor state logic; a common trap is misinterpreting 2WAY as a problem when it actually indicates a healthy, non-adjacent relationship between two DROTHERs. Remember the key rule: on a broadcast network, DROTHERs only go FULL with the DR and BDR, so seeing 2WAY between two DROTHERs is perfectly normal. A helpful memory tip is “DROTHERs don’t talk to DROTHERs—they only chat with the DR and BDR.”
CCNA IP Routing Practice Question
This 200-301 practice question tests your understanding of ip routing. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. A key principle to apply: oSPF elects a Designated Router (DR) and Backup Designated Router (BDR) on broadcast multi-access networks to reduce adjacency complexity.. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Exhibit
R2#show ip ospf neighbor
Neighbor ID Pri State Dead Time Address Interface
2.2.2.2 1 FULL/DR 00:00:33 10.1.1.2 Gig0/0
3.3.3.3 1 2WAY/DROTHER 00:00:39 10.1.1.3 Gig0/0
Exhibit: OSPF neighbors are not reaching FULL state on an Ethernet segment with multiple routers. The output of show ip ospf neighbor on R2 shows a neighbor in the 2WAY/DROTHER state. What is the most likely reason?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
R2#show ip ospf neighbor
Neighbor ID Pri State Dead Time Address Interface
2.2.2.2 1 FULL/DR 00:00:33 10.1.1.2 Gig0/0
3.3.3.3 1 2WAY/DROTHER 00:00:39 10.1.1.3 Gig0/0
A
Authentication mismatch between R2 and 3.3.3.3
Why wrong: A mismatch would stop the neighbor relationship from reaching 2WAY in the first place.
B
The 2WAY state with another DROTHER on a broadcast segment is normal
DROTHER routers do not form full adjacency with every other DROTHER.
C
R2 must be configured as a point-to-point network type
Why wrong: That is not required here and would change behavior rather than explain the current normal state.
D
R2 has a duplicate router ID
Why wrong: A duplicate router ID causes other issues and is not what this output indicates.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The 2WAY state with another DROTHER on a broadcast segment is normal
On a broadcast Ethernet network, two routers normally become fully adjacent through the DR or BDR. If the local router is stuck in 2WAY with another DROTHER, that is normal behavior. It is not a fault by itself.
Key principle: OSPF elects a Designated Router (DR) and Backup Designated Router (BDR) on broadcast multi-access networks to reduce adjacency complexity.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Authentication mismatch between R2 and 3.3.3.3
Why it's wrong here
A mismatch would stop the neighbor relationship from reaching 2WAY in the first place.
When this WOULD be correct
In a different question setup where the context involves OSPF neighbors failing to establish any adjacency due to mismatched authentication settings, option A would be correct. For example, if the question described a scenario where both routers are configured with different OSPF authentication methods, this option would accurately identify the problem.
✓
The 2WAY state with another DROTHER on a broadcast segment is normal
Why this is correct
DROTHER routers do not form full adjacency with every other DROTHER.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
OSPF elects a Designated Router (DR) and Backup Designated Router (BDR) on broadcast multi-access networks to reduce adjacency complexity.
✗
R2 must be configured as a point-to-point network type
Why it's wrong here
That is not required here and would change behavior rather than explain the current normal state.
When this WOULD be correct
In a different scenario where the question specifies that R2 is connected to a point-to-point link rather than a broadcast segment, configuring R2 as a point-to-point network type would be necessary to establish a full OSPF adjacency with its neighbor.
✗
R2 has a duplicate router ID
Why it's wrong here
A duplicate router ID causes other issues and is not what this output indicates.
When this WOULD be correct
In a different scenario where the question specifies that R2 is part of an OSPF network where multiple routers have been assigned the same router ID, this option would be correct as it would directly cause OSPF to fail to establish proper neighbor relationships.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.
✓The 2WAY state with another DROTHER on a broadcast segment is normalCorrect answer▾
Why this is correct
DROTHER routers do not form full adjacency with every other DROTHER.
✗Authentication mismatch between R2 and 3.3.3.3Wrong answer — click to see why▾
Why this is wrong here
An authentication mismatch would prevent OSPF neighbors from forming any adjacency; they would not reach the 2WAY state. The output shows neighbors in 2WAY state, indicating that authentication is not the issue.
★ When this WOULD be the correct answer
In a different question setup where the context involves OSPF neighbors failing to establish any adjacency due to mismatched authentication settings, option A would be correct. For example, if the question described a scenario where both routers are configured with different OSPF authentication methods, this option would accurately identify the problem.
Why candidates choose this
Students often associate neighbor issues with authentication mismatches, but the 2WAY state proves that the routers have successfully exchanged Hello packets, which includes authentication checks.
✗R2 must be configured as a point-to-point network typeWrong answer — click to see why▾
Why this is wrong here
Configuring the interface as point-to-point would change the OSPF network type, eliminating the need for DR/BDR election and causing all routers to form full adjacencies. However, the current 2WAY state is normal for a broadcast network, so changing the network type is unnecessary and not the reason for the observed state.
★ When this WOULD be the correct answer
In a different scenario where the question specifies that R2 is connected to a point-to-point link rather than a broadcast segment, configuring R2 as a point-to-point network type would be necessary to establish a full OSPF adjacency with its neighbor.
Why candidates choose this
Students may think that changing to point-to-point solves adjacency issues, but here the 2WAY state is expected, not a problem. The point-to-point type would force full adjacencies but is not required.
✗R2 has a duplicate router IDWrong answer — click to see why▾
Why this is wrong here
A duplicate router ID would cause OSPF to reject Hello packets from the router with the duplicate ID, preventing any neighbor relationship from forming. The output shows neighbors in 2WAY state, which indicates that router IDs are unique and Hello packets are being exchanged successfully.
★ When this WOULD be the correct answer
In a different scenario where the question specifies that R2 is part of an OSPF network where multiple routers have been assigned the same router ID, this option would be correct as it would directly cause OSPF to fail to establish proper neighbor relationships.
Why candidates choose this
Duplicate router IDs are a common OSPF misconfiguration, but they would prevent the neighbor state from progressing beyond DOWN or INIT, not reach 2WAY.
Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Common exam traps
Common exam trap: answer the scenario, not the keyword
A common exam trap is assuming that neighbors stuck in the 2-Way state indicate a problem requiring troubleshooting or configuration changes. Many candidates mistakenly believe that all OSPF neighbors on a broadcast segment must reach the FULL state with each other. However, OSPF’s design limits full adjacency to DR and BDR routers only. DROTHER routers remain in 2-Way state with each other, which is normal and expected. Misinterpreting this behavior can lead to incorrect answers such as blaming authentication or router ID issues when the output actually reflects standard OSPF operation.
Trap categories for this question
Command / output trap
A duplicate router ID causes other issues and is not what this output indicates.
Detailed technical explanation
How to think about this question
Open Shortest Path First (OSPF) is a link-state routing protocol that establishes neighbor adjacencies to exchange routing information. On broadcast multi-access networks like Ethernet, OSPF elects a Designated Router (DR) and a Backup Designated Router (BDR) to reduce the number of adjacencies and minimize flooding. Routers that are neither DR nor BDR assume the DROTHER role and form full adjacencies only with the DR and BDR, not with other DROTHER routers. This behavior optimizes network efficiency and reduces unnecessary overhead on the segment.
The OSPF neighbor state machine progresses through several states: Down, Init, 2-Way, ExStart, Exchange, Loading, and Full. On a broadcast segment, routers reach the 2-Way state with all neighbors but only form full adjacencies with the DR and BDR. Therefore, seeing a neighbor stuck in the 2-Way state with another DROTHER router is expected and indicates normal OSPF operation. Full adjacency is only required between DR/BDR and DROTHER routers, not between DROTHER routers themselves.
A common exam trap is to misinterpret the 2-Way state with a DROTHER neighbor as a problem or misconfigure network types to force full adjacency. However, this is standard OSPF behavior on broadcast networks and not a fault. Understanding this prevents unnecessary troubleshooting and misconfiguration. In practical networks, this design reduces CPU and bandwidth usage by limiting full adjacencies to only essential routers, improving scalability and stability.
KKey Concepts to Remember
OSPF elects a Designated Router (DR) and Backup Designated Router (BDR) on broadcast multi-access networks to reduce adjacency complexity.
Routers in the DROTHER role form full OSPF adjacencies only with the DR and BDR, not with other DROTHER routers on the same segment.
The OSPF neighbor state 2-Way indicates bidirectional communication but does not guarantee full adjacency with all neighbors on broadcast networks.
Full OSPF adjacency is established between DR/BDR and DROTHER routers, while DROTHER routers remain in 2-Way state with each other.
OSPF network types influence adjacency formation; broadcast network type automatically elects DR/BDR and manages neighbor states accordingly.
Authentication mismatches prevent OSPF neighbors from reaching 2-Way state, so adjacency stuck at 2-Way is not caused by authentication issues.
Duplicate router IDs cause OSPF neighbor relationship failures but do not manifest as neighbors stuck in 2-Way with DROTHER routers.
Configuring a point-to-point network type on a broadcast segment changes adjacency behavior and is unnecessary for normal Ethernet OSPF operation.
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.
Key takeaway
OSPF elects a Designated Router (DR) and Backup Designated Router (BDR) on broadcast multi-access networks to reduce adjacency complexity.
Real-world example
How this comes up in practice
A network engineer at a university connects two campus buildings via a fibre link. Both routers run OSPF, but no adjacency forms — even though both routers can ping each other. The engineer finds one router is in area 0 and the other in area 1. OSPF adjacency requires matching area numbers, hello/dead timers, and network type. IP reachability alone is not enough.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 200-301 question in full detail.
Review oSPF elects a Designated Router (DR) and Backup Designated Router (BDR) on broadcast multi-access networks to reduce adjacency complexity., then practise related 200-301 questions on the same topic to reinforce the concept.
IP Routing — This question tests IP Routing — OSPF elects a Designated Router (DR) and Backup Designated Router (BDR) on broadcast multi-access networks to reduce adjacency complexity..
What is the correct answer to this question?
The correct answer is: The 2WAY state with another DROTHER on a broadcast segment is normal — On a broadcast Ethernet network, two routers normally become fully adjacent through the DR or BDR. If the local router is stuck in 2WAY with another DROTHER, that is normal behavior. It is not a fault by itself.
What should I do if I get this 200-301 question wrong?
Review oSPF elects a Designated Router (DR) and Backup Designated Router (BDR) on broadcast multi-access networks to reduce adjacency complexity., then practise related 200-301 questions on the same topic to reinforce the concept.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
OSPF elects a Designated Router (DR) and Backup Designated Router (BDR) on broadcast multi-access networks to reduce adjacency complexity.
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