The correct answer is that the 2WAY/DROTHER state is normal on a broadcast network segment, as DROTHER routers do not form a full adjacency with each other. On OSPF broadcast multiaccess networks, only the Designated Router (DR) and Backup Designated Router (BDR) establish a FULL adjacency with every other router on the segment; all other routers, called DROTHERs, stop at the 2-Way state with each other to reduce routing update flooding and unnecessary overhead. This concept is frequently tested on the CCNA 200-301 v2 exam, often as a trick where you see a 2WAY/DROTHER neighbor and must recognize it is not a problem—the trap is assuming every neighbor must reach FULL. A quick memory tip: DROTHERs are “just friends, not best friends”—they exchange hellos (2-Way) but skip the full database exchange reserved for 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 forms full adjacencies only with the Designated Router (DR) and Backup Designated Router (BDR) on broadcast multiaccess networks.. 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.
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
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
This can be normal on a broadcast segment where DROTHER routers remain in 2-Way
On broadcast OSPF networks, full adjacency is typically formed with the DR and BDR. DROTHER routers can remain in the 2-Way state with one another and still be operating normally.
Key principle: OSPF forms full adjacencies only with the Designated Router (DR) and Backup Designated Router (BDR) on broadcast multiaccess networks.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
R1 has failed to form adjacency with 10.1.1.3
Why it's wrong here
A 2-Way state here is not automatically a failure.
When this WOULD be correct
In a different scenario where the question specifies that R1 is supposed to establish a full adjacency with all neighbors on a point-to-point link, and the output shows that it has not formed an adjacency with 10.1.1.3, then option A would be correct.
✓
This can be normal on a broadcast segment where DROTHER routers remain in 2-Way
Why this is correct
Correct. This is normal DR/DROTHER behavior on many multiaccess networks.
Related concept
OSPF forms full adjacencies only with the Designated Router (DR) and Backup Designated Router (BDR) on broadcast multiaccess networks.
✗
R1 has a duplicate router ID with 10.1.1.3
Why it's wrong here
The output does not indicate a duplicate router ID.
When this WOULD be correct
If the question stated that R1 was unable to establish any OSPF neighbor relationships at all, or if it showed that 10.1.1.3 was not listed in the OSPF neighbor table, then stating that R1 has a duplicate router ID with 10.1.1.3 would be correct, as it would prevent adjacency formation.
✗
The interface is passive
Why it's wrong here
A passive interface would not form neighbors at all.
When this WOULD be correct
If the question provided output indicating that the OSPF interface was configured as passive (e.g., showing no OSPF neighbors), then stating that the interface is passive would be correct. The question would need to focus on the configuration of OSPF interfaces.
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.
✓This can be normal on a broadcast segment where DROTHER routers remain in 2-WayCorrect answer▾
Why this is correct
Correct. This is normal DR/DROTHER behavior on many multiaccess networks.
✗R1 has failed to form adjacency with 10.1.1.3Wrong answer — click to see why▾
Why this is wrong here
The 2-Way state is a normal OSPF neighbor state on broadcast multiaccess networks for non-DR/BDR routers (DROTHERs). It indicates that bidirectional communication has been established, but full adjacency is not required because they do not exchange LSAs directly. This is not a failure.
★ When this WOULD be the correct answer
In a different scenario where the question specifies that R1 is supposed to establish a full adjacency with all neighbors on a point-to-point link, and the output shows that it has not formed an adjacency with 10.1.1.3, then option A would be correct.
Why candidates choose this
Students often associate the 2-Way state with incomplete adjacency or a problem, but in OSPF, 2-Way is a valid state for DROTHERs on broadcast segments. They may confuse it with the INIT or EXSTART states, which indicate issues.
✗R1 has a duplicate router ID with 10.1.1.3Wrong answer — click to see why▾
Why this is wrong here
A duplicate router ID would cause OSPF neighbor state to oscillate or remain in EXSTART/EXCHANGE, not stabilize in 2-Way. The output shows a stable 2-Way state, which is normal for DROTHERs. Duplicate IDs would also generate error messages in the logs.
★ When this WOULD be the correct answer
If the question stated that R1 was unable to establish any OSPF neighbor relationships at all, or if it showed that 10.1.1.3 was not listed in the OSPF neighbor table, then stating that R1 has a duplicate router ID with 10.1.1.3 would be correct, as it would prevent adjacency formation.
Why candidates choose this
Test-takers might think that any unusual neighbor state (like 2-Way) indicates a duplicate ID, but 2-Way is actually a normal state for non-DR/BDR neighbors. They may confuse the 2-Way state with the DOWN or ATTEMPT states that occur with duplicate IDs.
✗The interface is passiveWrong answer — click to see why▾
Why this is wrong here
A passive interface in OSPF does not send Hello packets and therefore cannot form any neighbor adjacency. The output shows two neighbors in valid states (FULL and 2-Way), which proves the interface is active and sending Hellos.
★ When this WOULD be the correct answer
If the question provided output indicating that the OSPF interface was configured as passive (e.g., showing no OSPF neighbors), then stating that the interface is passive would be correct. The question would need to focus on the configuration of OSPF interfaces.
Why candidates choose this
Students may think that a passive interface prevents full adjacency, but it actually prevents any adjacency at all. The presence of neighbors in the output contradicts the passive interface assumption.
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
Be cautious not to confuse the 2WAY state with being a BDR or DR. Understand the significance of FULL/DR and 2WAY/DROTHER states.
Trap categories for this question
Command / output trap
The output does not indicate a duplicate router ID.
Detailed technical explanation
How to think about this question
OSPF (Open Shortest Path First) is a link-state routing protocol that uses a series of neighbor states to establish adjacencies between routers. On broadcast multiaccess networks such as Ethernet, OSPF elects a Designated Router (DR) and a Backup Designated Router (BDR) to reduce the number of adjacencies required. Routers that are neither DR nor BDR are called DROTHERs. These DROTHER routers form full adjacencies only with the DR and BDR, but remain in the 2-Way state with other DROTHER routers.
The 2-Way state means that bidirectional communication has been established through the exchange of hello packets, and the routers recognize each other as neighbors. However, full adjacency, which involves database synchronization and exchange of link-state advertisements (LSAs), only occurs between DR/BDR and DROTHER routers. This behavior optimizes OSPF operation by limiting the number of full adjacencies on a broadcast segment.
In the provided output, R1 shows a FULL/DR state with neighbor 10.1.1.2, indicating that R1 is the DR and has formed a full adjacency with that neighbor. The 2WAY/DROTHER state with 10.1.1.3 is normal and expected behavior for DROTHER routers on a broadcast network segment. This confirms that R1 has not failed to form adjacency with 10.1.1.3; rather, it is operating correctly according to OSPF design.
Understanding these OSPF neighbor states and roles is essential for troubleshooting OSPF adjacency issues and ensuring efficient routing. Misinterpreting the 2-Way state as a failure can lead to unnecessary troubleshooting steps. Additionally, passive interfaces do not form neighbors at all, and duplicate router IDs cause different symptoms, such as adjacency flapping or failure to form neighbors entirely.
KKey Concepts to Remember
OSPF forms full adjacencies only with the Designated Router (DR) and Backup Designated Router (BDR) on broadcast multiaccess networks.
Routers in DROTHER roles on a broadcast segment remain in the 2-Way state with other DROTHER routers and do not form full adjacencies with them.
The 2-Way state in OSPF indicates bidirectional communication and neighbor recognition but not full adjacency.
A passive interface in OSPF does not send or receive OSPF hello packets and therefore does not form any neighbor relationships.
Duplicate router IDs in OSPF cause adjacency formation issues but are not indicated solely by neighbor states like 2-Way or Full.
OSPF neighbor states progress from Down, Init, 2-Way, to Full, with Full indicating a fully established adjacency.
The Designated Router (DR) election process assigns roles based on priority and router ID to optimize OSPF adjacency formation on multiaccess networks.
OSPF adjacency states and roles (DR, BDR, DROTHER) are critical for efficient link-state database synchronization and routing stability.
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 forms full adjacencies only with the Designated Router (DR) and Backup Designated Router (BDR) on broadcast multiaccess networks.
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 forms full adjacencies only with the Designated Router (DR) and Backup Designated Router (BDR) on broadcast multiaccess networks., then practise related 200-301 questions on the same topic to reinforce the concept.
IP Routing — This question tests IP Routing — OSPF forms full adjacencies only with the Designated Router (DR) and Backup Designated Router (BDR) on broadcast multiaccess networks..
What is the correct answer to this question?
The correct answer is: This can be normal on a broadcast segment where DROTHER routers remain in 2-Way — On broadcast OSPF networks, full adjacency is typically formed with the DR and BDR. DROTHER routers can remain in the 2-Way state with one another and still be operating normally.
What should I do if I get this 200-301 question wrong?
Review oSPF forms full adjacencies only with the Designated Router (DR) and Backup Designated Router (BDR) on broadcast multiaccess networks., then practise related 200-301 questions on the same topic to reinforce the concept.
What is the key concept behind this question?
OSPF forms full adjacencies only with the Designated Router (DR) and Backup Designated Router (BDR) on broadcast multiaccess networks.
About these practice questions
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These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A router output shows this neighbor state:
Neighbor ID 10.1.1.1 State FULL/DR Address 192.168.12.1
What does the FULL/DR state indicate?
medium
A.The local router is the DR and adjacency formation has failed
✓ B.The neighbor relationship is complete and the neighbor is the DR on that segment
C.The routers are exchanging only link-state requests
D.The neighbor has been learned through BGP redistribution
Why B: FULL means the OSPF adjacency is fully formed. The /DR suffix indicates that the listed neighbor is the Designated Router for that multiaccess segment.
Last reviewed: May 17, 2026
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