CCNA IP Routing Practice Question
A technician is troubleshooting an OSPF adjacency problem: R1 and R2 are not forming a neighbor relationship. R1's OSPF configuration includes the command 'network 192.168.1.0 0.0.0.255 area 0'. R2's GigabitEthernet0/0 is configured with IP address 10.1.1.1/30 and is participating in OSPF area 0. The engineer verifies that physical connectivity is fine and OSPF is enabled on R2. What is the most likely cause?
⚠ Common exam trap
Cisco often tests the concept that the OSPF network statement must match the exact subnet of the interface connecting the routers, not just any subnet in the router's routing table, to ensure OSPF is enabled on the correct interface.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
R1's network statement does not include the subnet of the link connecting R1 and R2.
R1's network statement 'network 192.168.1.0 0.0.0.255 area 0' only enables OSPF on interfaces whose IP addresses fall within the 192.168.1.0/24 range. The link between R1 and R2 uses the 10.1.1.0/30 subnet (R2's GigabitEthernet0/0 is 10.1.1.1/30), so R1's interface on that link is not covered by the network statement. Without OSPF enabled on the connecting interface, R1 cannot send or receive OSPF hello packets, preventing neighbor adjacency formation.
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 network type on R1's interface differs from the network type on R2's interface.
Why it's wrong here
By default, Ethernet interfaces use the broadcast network type. Unless explicitly changed, both routers will have the same type, so this is unlikely to be the cause. The configuration shown does not indicate any network type changes.
- ✓
R1's network statement does not include the subnet of the link connecting R1 and R2.
Why this is correct
The command 'network 192.168.1.0 0.0.0.255 area 0' only enables OSPF on interfaces with an IP address in the 192.168.1.0/24 range. The link uses the 10.1.1.0/30 subnet, so R1's interface (e.g., 10.1.1.2/30) is not matched. Consequently, OSPF is inactive on that interface, and no neighbor relationship can form.
- ✗
R1's router ID is not manually set and duplicates the router ID of R2.
Why it's wrong here
A duplicate router ID would cause adjacency problems and log an error, but the scenario provides no evidence of this. The immediate and direct cause based on the configuration snippet is the network command mismatch.
- ✗
Mismatched OSPF hello and dead intervals between the routers.
Why it's wrong here
Hello and dead interval mismatches prevent adjacency, but the question does not indicate that any timers have been modified from their default values. The most likely cause given the explicit network command is the missing subnet match.
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.
✓R1's network statement does not include the subnet of the link connecting R1 and R2.Correct answer▾
Why this is correct
The command 'network 192.168.1.0 0.0.0.255 area 0' only enables OSPF on interfaces with an IP address in the 192.168.1.0/24 range. The link uses the 10.1.1.0/30 subnet, so R1's interface (e.g., 10.1.1.2/30) is not matched. Consequently, OSPF is inactive on that interface, and no neighbor relationship can form.
✗The OSPF network type on R1's interface differs from the network type on R2's interface.Wrong answer — click to see why▾
Why this is wrong here
Candidates assume that OSPF adjacency failures on Ethernet links are often due to network type mismatches, without considering that the default settings match.
✗R1's router ID is not manually set and duplicates the router ID of R2.Wrong answer — click to see why▾
Why this is wrong here
Candidates may remember that duplicate router‑IDs break OSPF and jump to this conclusion without first analyzing the simpler configuration issue.
✗Mismatched OSPF hello and dead intervals between the routers.Wrong answer — click to see why▾
Why this is wrong here
Many students learn that timer mismatches are a common OSPF problem and may incorrectly assume they are the cause when the real issue is a basic configuration oversight.
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?”
Visual reference
Quick reference
Routing Protocol Comparison
| Protocol | Metric | Max Hops | Algorithm | Type |
|---|---|---|---|---|
| RIP v2 | Hop count | 15 | Bellman-Ford | Distance vector |
| OSPF | Cost (bandwidth) | Unlimited | Dijkstra (SPF) | Link state |
| EIGRP | Composite metric | Unlimited | DUAL | Hybrid |
| IS-IS | Cost | Unlimited | Dijkstra | Link state |
| BGP | Policy / attributes | Unlimited | Path vector | Path vector |
RIP's 15-hop limit makes it unsuitable for large networks. OSPF and EIGRP dominate modern enterprise deployments.
Go deeper
Related to this question
Learn chapter
OSPFv3 Single-Area Configuration for IPv6
Key term
OSPF
OSPF is a link-state routing protocol used to find the best path for data packets to travel across IP networks, like a smart GPS that recalculates routes when traffic changes.
Key term
Interface
An interface is a point of connection or interaction between two systems, devices, or software components that allows them to exchange information or signals.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 200-301 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 200-301 exam.