The correct statement is that Router R1 has a full adjacency with both neighbors in OSPFv3. This is because the output of the show ipv6 ospf neighbor command displays both neighbors in the FULL state, with the roles of Backup Designated Router (BDR) and Designated Router (DR) indicated after the slash—FULL/BDR for 10.1.1.2 and FULL/DR for 10.1.1.3. The key technical concept here is that OSPFv3 neighbor adjacency troubleshooting hinges on recognizing that the FULL state confirms a complete exchange of link-state information, regardless of the DR/BDR designation, and that the neighbor IDs are router IDs while the actual next-hop addresses are link-local IPv6 addresses (FE80::). On the Cisco CCNP ENARSI 300-410 exam, this question tests your ability to read OSPFv3 neighbor output accurately and avoid the common trap of confusing the router ID with the IPv6 address used for routing. A useful memory tip: in OSPFv3, always look for the FULL state first—the role after the slash (DR/BDR/DROTHER) only matters for multi-access network behavior, not adjacency health.
300-410 OSPF Troubleshooting (v2/v3) Practice Question
This 300-410 practice question tests your understanding of ospf troubleshooting (v2/v3). Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. 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 network engineer runs the following command on Router R1:
R1# show ipv6 ospf neighbor
Neighbor ID Pri State Dead Time Address Interface
10.1.1.2 1 FULL/BDR 00:00:35 FE80::2 GigabitEthernet0/0
10.1.1.3 1 FULL/DR 00:00:32 FE80::3 GigabitEthernet0/1
Based on this output, which statement is correct regarding OSPFv3?
Router R1 is the DR on the segment connected to GigabitEthernet0/0.
Why wrong: The neighbor is BDR, so R1 might be DR, but the output does not show R1's own state; the neighbor state is BDR, indicating the neighbor is not DR.
B
Router R1 has a full adjacency with both neighbors in OSPFv3.
Both neighbors show FULL state, indicating complete adjacency in OSPFv3.
C
The OSPFv3 process is using IPv4 addresses as router IDs.
Why wrong: The neighbor IDs are shown as IPv4 addresses (10.1.1.2, 10.1.1.3), which is common in OSPFv3; router IDs are 32-bit numbers, often represented as IPv4 addresses.
D
Router R1 is not receiving hello packets from 10.1.1.3.
Why wrong: The state is FULL, so hello packets are being received.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Router R1 has a full adjacency with both neighbors in OSPFv3.
The output shows OSPFv3 neighbors. The neighbor 10.1.1.2 is in state FULL/BDR, meaning it is the Backup Designated Router. The neighbor 10.1.1.3 is in state FULL/DR, meaning it is the Designated Router. The addresses are link-local IPv6 addresses.
Key principle: OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Router R1 is the DR on the segment connected to GigabitEthernet0/0.
Why it's wrong here
The neighbor is BDR, so R1 might be DR, but the output does not show R1's own state; the neighbor state is BDR, indicating the neighbor is not DR.
✓
Router R1 has a full adjacency with both neighbors in OSPFv3.
Why this is correct
Both neighbors show FULL state, indicating complete adjacency in OSPFv3.
The OSPFv3 process is using IPv4 addresses as router IDs.
Why it's wrong here
The neighbor IDs are shown as IPv4 addresses (10.1.1.2, 10.1.1.3), which is common in OSPFv3; router IDs are 32-bit numbers, often represented as IPv4 addresses.
✗
Router R1 is not receiving hello packets from 10.1.1.3.
Why it's wrong here
The state is FULL, so hello packets are being received.
Common exam traps
Common exam trap: OSPF can fail even when IP connectivity looks correct
OSPF neighbour formation depends on matching areas, timers, network type, authentication and passive-interface behaviour. Do not choose an answer only because the devices can ping.
Trap categories for this question
Command / output trap
The neighbor is BDR, so R1 might be DR, but the output does not show R1's own state; the neighbor state is BDR, indicating the neighbor is not DR.
Detailed technical explanation
How to think about this question
OSPF questions usually test the details that control adjacency and route selection. Read the neighbour state, area, router ID and interface configuration before deciding what is wrong.
KKey Concepts to Remember
OSPF neighbours must agree on key parameters.
Router ID selection can affect neighbour relationships and LSDB output.
OSPF cost influences the preferred path.
A route can appear in OSPF information but not become the installed route.
TExam Day Tips
→Check area mismatch first when OSPF adjacency fails.
→Review passive interfaces when a network is advertised but no neighbour forms.
→Use show ip ospf neighbor and show ip route clues carefully.
Key takeaway
OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
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 300-410 question in full detail.
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related 300-410 OSPF questions on adjacency and route selection.
OSPF Troubleshooting (v2/v3) — This question tests OSPF Troubleshooting (v2/v3) — OSPF neighbours must agree on key parameters..
What is the correct answer to this question?
The correct answer is: Router R1 has a full adjacency with both neighbors in OSPFv3. — The output shows OSPFv3 neighbors. The neighbor 10.1.1.2 is in state FULL/BDR, meaning it is the Backup Designated Router. The neighbor 10.1.1.3 is in state FULL/DR, meaning it is the Designated Router. The addresses are link-local IPv6 addresses.
What should I do if I get this 300-410 question wrong?
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related 300-410 OSPF questions on adjacency and route selection.
What is the key concept behind this question?
OSPF neighbours must agree on key parameters.
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Variation 1. Which TWO statements correctly describe the behavior of OSPFv3 when troubleshooting neighbor adjacency issues on a Cisco IOS-XE router? (Choose TWO.)
hard
✓ A.OSPFv3 neighbor adjacencies are formed using the link-local IPv6 address of the neighbor.
B.The OSPFv3 router ID is a 128-bit value derived from the highest loopback IPv6 address.
C.The 'ipv6 router ospf' command is used to enable OSPFv3 on an interface.
✓ D.The 'show ipv6 ospf neighbor' command displays the link-local address of each neighbor.
E.OSPFv3 uses the network type configured under the OSPFv3 process globally, not per interface.
Why A: OSPFv3 uses link-local addresses for neighbor adjacency formation and relies on IPv6 link-local addresses for next-hop resolution. The router ID is still a 32-bit value, and the network type must be configured under the interface. The 'ipv6 ospf' command is used to enable OSPFv3 on an interface, not 'ipv6 router ospf'.
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