The answer is that the OSPF adjacency formed successfully, with 10.1.1.1 as the Designated Router and 10.1.1.2 as the Backup Designated Router. This is correct because the debug output for OSPF adjacency verification VRF shows the neighbor transitioning through the standard OSPF states—from 2-Way, through DR election, to the FULL state—which is the definitive indication of a complete adjacency. The command `debug ip ospf adj vrf CUSTOMER_C` is specifically used to isolate OSPF adjacency events within a VRF-Lite context, and the output confirms that both routers exchanged database descriptors and link-state advertisements without errors. On the Cisco CCNP ENARSI 300-410 exam, this scenario tests your ability to interpret debug logs for multi-VRF environments, a common troubleshooting task where a common trap is misreading the 2-Way state as incomplete. Remember the memory tip: “2-Way means hello, FULL means all good”—if you see FULL, the adjacency is up, regardless of DR/BDR roles.
300-410 VRF-Lite Practice Question
This 300-410 practice question tests your understanding of vrf-lite. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 to troubleshoot a VRF-Lite OSPF adjacency issue:
R1# debug ip ospf adj vrf CUSTOMER_C
Output:
OSPF: 2 Way state received from 10.1.1.2 on interface GigabitEthernet0/1, address 10.1.1.2
OSPF: Neighbor 10.1.1.2 is eligible for DR election on interface GigabitEthernet0/1
OSPF: DR election: 10.1.1.1 (pri 1) is DR, 10.1.1.2 (pri 1) is BDR
OSPF: Build router LSA for area 0, router ID 1.1.1.1, seq 0x80000001
OSPF: Neighbor 10.1.1.2 is FULL, state changed from LOADING to FULL
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The OSPF adjacency formed successfully, with 10.1.1.1 as DR and 10.1.1.2 as BDR.
The 'debug ip ospf adj vrf' command shows OSPF adjacency state changes for a specific VRF. The output shows a successful OSPF adjacency formation: the neighbor transitioned through 2-Way, DR election, and reached FULL state. The router with IP 10.1.1.1 became the DR, and 10.1.1.2 became the BDR.
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.
✗
The OSPF adjacency failed because the neighbor remained in LOADING state.
Why it's wrong here
Incorrect. The neighbor changed from LOADING to FULL, indicating success.
✓
The OSPF adjacency formed successfully, with 10.1.1.1 as DR and 10.1.1.2 as BDR.
Why this is correct
Correct. The debug shows FULL state and DR/BDR election results.
The OSPF adjacency formed but the router ID is missing, causing instability.
Why it's wrong here
Incorrect. The router ID 1.1.1.1 is shown in the build router LSA message.
✗
The OSPF adjacency is stuck in 2-Way state due to mismatched area IDs.
Why it's wrong here
Incorrect. The debug shows transition from 2-Way to DR election and then FULL.
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
Incorrect. The router ID 1.1.1.1 is shown in the build router LSA message.
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.
VRF-Lite — This question tests VRF-Lite — OSPF neighbours must agree on key parameters..
What is the correct answer to this question?
The correct answer is: The OSPF adjacency formed successfully, with 10.1.1.1 as DR and 10.1.1.2 as BDR. — The 'debug ip ospf adj vrf' command shows OSPF adjacency state changes for a specific VRF. The output shows a successful OSPF adjacency formation: the neighbor transitioned through 2-Way, DR election, and reached FULL state. The router with IP 10.1.1.1 became the DR, and 10.1.1.2 became the BDR.
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.
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 network engineer runs the following command on Router R1:
R1# show ip ospf neighbor vrf BLUE
Neighbor ID Pri State Dead Time Address Interface
10.0.0.2 1 FULL/DR 00:00:32 10.1.1.2 GigabitEthernet0/0
10.0.0.3 1 2WAY/DROTHER 00:00:35 10.1.2.2 GigabitEthernet0/1
Based on this output, which statement is correct?
medium
A.Neighbor 10.0.0.3 is not forming a full adjacency because it is a DROTHER.
B.Neighbor 10.0.0.2 is the Backup Designated Router.
C.Both neighbors are in the FULL state.
✓ D.The OSPF adjacencies are functioning normally.
Why D: The output shows two OSPF neighbors for VRF BLUE. Neighbor 10.0.0.2 is in FULL state and is the DR on GigabitEthernet0/0. Neighbor 10.0.0.3 is in 2WAY state and is a DROTHER on GigabitEthernet0/1. The 2WAY state is normal for neighbors that are not DR/BDR on a multi-access network. No problem is evident.
Last reviewed: Jun 18, 2026
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