Question 1hardmultiple choice
Full question →hardmultiple choiceObjective-mapped
Two OSPF routers connected on an Ethernet link remain in the INIT state. Which issue is the most likely cause?
Answer choices
Why each option matters
Good practice is not just finding the correct option. The wrong answers often show the exact trap the exam wants you to fall into.
A
Distractor review
The routers have identical router IDs
Duplicate router IDs cause problems, but INIT more commonly points to one-way communication.
B
Best answer
The routers cannot exchange Hellos bidirectionally on the segment
Correct. INIT often indicates one-way Hello communication.
C
Distractor review
The routers have already reached FULL and are waiting to install routes
FULL is a later state.
D
Distractor review
The routers are using the same OSPF process ID
The process ID is locally significant and not exchanged.
Common exam trap
Common exam trap: answer the scenario, not the keyword
A common exam trap is to assume that duplicate router IDs cause routers to remain stuck in the INIT state. While duplicate router IDs do cause adjacency issues, they typically result in different neighbor states or error messages, not the INIT state specifically. Another trap is to think that using the same OSPF process ID on both routers causes adjacency failure; however, the process ID is locally significant and does not affect neighbor formation. Misinterpreting the INIT state as a sign of routers already being fully adjacent or waiting to install routes is also incorrect, as FULL is a later state. The key is to recognize that INIT indicates one-way Hello communication, often due to Layer 2 or multicast issues.
Technical deep dive
How to think about this question
OSPF (Open Shortest Path First) is a link-state routing protocol that establishes neighbor relationships by exchanging Hello packets on a common network segment. When two OSPF routers connect on an Ethernet link, they must successfully exchange Hello packets bidirectionally to progress through the neighbor states from Down to Init, then to 2-Way, and eventually to Full adjacency. The INIT state indicates that a router has received a Hello packet from its neighbor but has not yet seen its own router ID listed in the neighbor's Hello packet, meaning the communication is only one-way. The OSPF neighbor state machine requires that routers see their own router ID in the neighbor field of received Hello packets to confirm bidirectional communication. If routers remain stuck in the INIT state, it usually means that one router can hear the other, but the reverse is not true. This can be caused by Layer 2 issues such as VLAN mismatches, incorrect interface configurations, or multicast filtering that blocks OSPF Hello packets. The OSPF process ID is locally significant and does not affect neighbor formation, so it is not a cause of this problem. A common exam trap is to confuse the INIT state with other OSPF states or causes such as duplicate router IDs or process ID mismatches. Duplicate router IDs cause adjacency failures but typically result in different neighbor states or log messages. The INIT state specifically points to one-way Hello communication. In practical networks, verifying Layer 2 connectivity, multicast forwarding, and interface settings is critical to resolving INIT state issues and establishing full OSPF adjacency.
KKey Concepts to Remember
- OSPF routers must exchange Hello packets bidirectionally on a common network segment to progress beyond the INIT neighbor state.
- The INIT state means a router sees Hellos from its neighbor but does not see its own router ID in the neighbor field of received Hellos.
- One-way communication or Layer 2 issues such as VLAN mismatches or multicast filtering commonly cause OSPF routers to remain in the INIT state.
- OSPF process IDs are locally significant and do not affect neighbor adjacency or cause routers to remain in the INIT state.
- Duplicate router IDs cause adjacency problems but typically do not cause routers to remain stuck in the INIT state.
- OSPF adjacency states progress from Down to Init, then 2-Way, and finally Full, requiring bidirectional Hello packet exchange at each step.
- Multicast filtering or interface misconfigurations can block OSPF Hello packets, preventing routers from seeing each other's router IDs.
- Successful OSPF adjacency formation requires both Layer 2 connectivity and correct OSPF Hello packet exchange on the segment.
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.
Related practice questions
Related 200-301 practice-question pages
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
CCNA subnetting practice questions
Practise IPv4 subnetting, CIDR, masks, host ranges and subnet selection.
CCNA OSPF practice questions
Practise OSPF neighbours, router IDs, metrics, areas and routing-table interpretation.
CCNA VLAN practice questions
Practise VLANs, access ports, trunks, allowed VLANs and switching scenarios.
CCNA STP practice questions
Practise spanning tree, root bridge election, port roles and STP troubleshooting.
CCNA EtherChannel practice questions
Practise LACP, PAgP, port-channel behaviour and bundle requirements.
CCNA ACL practice questions
Practise standard and extended ACLs, permit/deny logic and traffic filtering.
CCNA NAT practice questions
Practise static NAT, dynamic NAT, PAT and inside/outside address translation.
CCNA DHCP practice questions
Practise DHCP scopes, relay, leases and troubleshooting.
CCNA show ip route practice questions
Practise routing-table output, longest-prefix match, AD and route selection.
CCNA show interfaces trunk practice questions
Practise trunk verification and VLAN forwarding across switches.
CCNA wireless security practice questions
Practise WLAN security, authentication and wireless architecture concepts.
CCNA IPv6 practice questions
Practise IPv6 addressing, routes, neighbour discovery and common IPv6 exam traps.
More questions from this exam
Keep practising from the same exam bank, or move into a focused topic page if this question exposed a weak area.
Question 1
A router learns the same prefix from both OSPF and EIGRP. Which route is installed by default?
Question 2
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 Which statement is correct?
Question 3
What is the OSPF metric called?
Question 4
A non-root switch has two uplinks toward the root bridge. One path has a lower total STP cost than the other. What role will the lower-cost uplink have?
Question 5
A router interface applies this ACL inbound: 10 deny tcp any any eq 80 20 permit ip any any A user reports that web browsing to a server by IP address fails, but ping works. Which statement best explains the behavior?
Question 6
A router learns route 198.51.100.0/24 from OSPF with AD 110 and also has a static route to the same prefix configured with AD 150. Which route is installed?
FAQ
Questions learners often ask
What does this 200-301 question test?
OSPF routers must exchange Hello packets bidirectionally on a common network segment to progress beyond the INIT neighbor state.
What is the correct answer to this question?
The correct answer is: The routers cannot exchange Hellos bidirectionally on the segment — INIT means a router is seeing Hellos from its neighbor but does not see its own router ID in the neighbor field of received Hellos. A common cause is one-way communication or a mismatched multicast/adjacency problem, often at Layer 2.
What should I do if I get this 200-301 question wrong?
Then try more questions from the same exam bank and focus on understanding why the wrong options are tempting.
Discussion
Loading comments…
Sign in to join the discussion.