This 350-401 practice question tests your understanding of ospf. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 issues the following command on Router R6:
R6# debug ip ospf hello
OSPF: Send hello to 224.0.0.5 via GigabitEthernet0/0 (192.168.1.6)
OSPF: Rcv hello from 1.1.1.1, GigabitEthernet0/0, area 0.0.0.0
R6 has formed a full adjacency with neighbor 1.1.1.1.
Why wrong: The state is 2WAY, not FULL.
B
The hello packet was sent to the DR/BDR multicast address 224.0.0.6.
Why wrong: The destination is 224.0.0.5, which is AllSPFRouters, not AllDRouters.
C
R6 and 1.1.1.1 are neighbors, but a full adjacency may not yet be formed.
2WAY is a valid neighbor state indicating two-way communication, but full adjacency requires further exchange (e.g., on broadcast networks, only with DR/BDR).
D
The OSPF network type is point-to-point.
Why wrong: Point-to-point networks skip the 2WAY state and go directly to FULL.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
R6 and 1.1.1.1 are neighbors, but a full adjacency may not yet be formed.
The debug output shows the neighbor state is 2WAY, which indicates that R6 has received a hello from 1.1.1.1 and bidirectional communication is established, but a full adjacency has not yet been formed. In OSPF, the 2WAY state is a prerequisite for advancing to the ExStart state and eventually to FULL, but on multiaccess networks, the router must also wait for the Designated Router (DR) and Backup Designated Router (BDR) election process to complete before proceeding. Therefore, option C correctly states that R6 and 1.1.1.1 are neighbors, but a full adjacency may not yet be formed.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
R6 has formed a full adjacency with neighbor 1.1.1.1.
Why it's wrong here
The state is 2WAY, not FULL.
✗
The hello packet was sent to the DR/BDR multicast address 224.0.0.6.
Why it's wrong here
The destination is 224.0.0.5, which is AllSPFRouters, not AllDRouters.
✓
R6 and 1.1.1.1 are neighbors, but a full adjacency may not yet be formed.
Why this is correct
2WAY is a valid neighbor state indicating two-way communication, but full adjacency requires further exchange (e.g., on broadcast networks, only with DR/BDR).
Related concept
Read the scenario before looking for a memorised answer.
✗
The OSPF network type is point-to-point.
Why it's wrong here
Point-to-point networks skip the 2WAY state and go directly to FULL.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between the 2WAY and FULL states, and the trap here is that candidates mistakenly assume that receiving a hello packet means a full adjacency has been formed, ignoring the multi-step OSPF neighbor state machine and the role of DR/BDR elections on broadcast networks.
Detailed technical explanation
How to think about this question
In OSPF, the 2WAY state is reached when a router sees its own Router ID in a neighbor's hello packet, confirming bidirectional communication. On broadcast multiaccess networks, routers must then participate in a DR/BDR election; only the DR and BDR form full adjacencies with all other routers (DROTHERs remain in 2WAY state with each other). The debug output shows 'options 0x2', which indicates the E-bit is set, meaning the router supports external routing (OSPFv2), and the hello is sent to 224.0.0.5 (AllSPFRouters) because all OSPF routers listen on this address for hello packets.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
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
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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 350-401 question in full detail.
OSPF — This question tests OSPF — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: R6 and 1.1.1.1 are neighbors, but a full adjacency may not yet be formed. — The debug output shows the neighbor state is 2WAY, which indicates that R6 has received a hello from 1.1.1.1 and bidirectional communication is established, but a full adjacency has not yet been formed. In OSPF, the 2WAY state is a prerequisite for advancing to the ExStart state and eventually to FULL, but on multiaccess networks, the router must also wait for the Designated Router (DR) and Backup Designated Router (BDR) election process to complete before proceeding. Therefore, option C correctly states that R6 and 1.1.1.1 are neighbors, but a full adjacency may not yet be formed.
What should I do if I get this 350-401 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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