CCNA IP Routing Practice Question
Network Topology
You have console access to both R1 and R2. Configure OSPFv2 on both routers to establish a single-area adjacency in area 0. The link between R1 and R2 uses 10.0.0.0/30. Currently, OSPF is not configured on either router. After configuration, verify the adjacency forms and routes are exchanged.
⚠ Common exam trap
Remember that OSPF network statements use wildcard masks, not subnet masks. Also, both routers must be configured; OSPF does not automatically enable on all interfaces. Use 'show ip ospf neighbor' to verify adjacency formation.
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
✓
Configure 'router ospf 1' on R1 and R2, set router-id, and use 'network 10.0.0.0 0.0.0.3 area 0' on both routers.
The essential requirement is enabling OSPFv2 on both routers with matching area 0 on the 10.0.0.0/30 link. On R1 and R2, enter 'router ospf 1', set a unique router-id, and use 'network 10.0.0.0 0.0.0.3 area 0' to advertise the link. The solution commands include optional networks (192.168.1.0/24 and Loopback0) that are not required for the adjacency and are shown only as examples; candidates should focus on the link network. After configuration, 'show ip ospf neighbor' should show a FULL state. Common mistakes include using a subnet mask instead of a wildcard mask (option C) or a /32 wildcard (option D), and not configuring OSPF on R2 (option B).
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Configure 'router ospf 1' on R1 and R2, set router-id, and use 'network 10.0.0.0 0.0.0.3 area 0' on both routers.
Why this is correct
This is correct because OSPFv2 requires a process ID, a unique router-id, and a network statement that matches the interface IP with a wildcard mask to enable OSPF on that interface in area 0. The wildcard mask 0.0.0.3 matches the /30 prefix exactly.
- ✗
Configure 'router ospf 1' on R1 only, and use 'network 10.0.0.0 0.0.0.3 area 0' on R1; R2 does not need OSPF configuration because it will learn routes via the directly connected interface.
Why it's wrong here
This configuration leaves R2 out of the OSPF process entirely. OSPF adjacency is a mutual exchange of Hello packets; if R2 does not run OSPF on the interface, no neighbor relationship forms and neither router will exchange OSPF routes. A directly connected interface is simply a connected route in R2's routing table—it is not injected into OSPF unless a network statement or redistribute command makes it part of the OSPF process. Both routers must be configured with OSPF and advertise the link in area 0 for the adjacency to come up.
- ✗
Configure 'router ospf 1' on both routers, set router-id, and use 'network 10.0.0.0 255.255.255.252 area 0' on both routers.
Why it's wrong here
The OSPF network command requires a wildcard mask, not a subnet mask. The wildcard mask is the bitwise inverse of the subnet mask: for a /30 prefix, the subnet mask is 255.255.255.252, so the wildcard mask is 0.0.0.3. Using 255.255.255.252 as the wildcard mask inverts the matching logic—OSPF would attempt to match bits that should be wildcards and ignore bits that must match—so the interface IP 10.0.0.1 or 10.0.0.2 would not be correctly matched. Consequently, OSPF would fail to enable on the intended interface and no adjacency would form.
- ✗
Configure 'router ospf 1' on both routers, set router-id, and use 'network 10.0.0.0 0.0.0.0 area 0' on both routers.
Why it's wrong here
This is incorrect because the wildcard mask 0.0.0.0 matches only the exact IP address 10.0.0.0, not the entire subnet. The interface IPs (10.0.0.1 and 10.0.0.2) would not be matched, so OSPF would not be enabled on the link.
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.
✓Configure 'router ospf 1' on R1 and R2, set router-id, and use 'network 10.0.0.0 0.0.0.3 area 0' on both routers.Correct answer▾
Why this is correct
This is correct because OSPFv2 requires a process ID, a unique router-id, and a network statement that matches the interface IP with a wildcard mask to enable OSPF on that interface in area 0. The wildcard mask 0.0.0.3 matches the /30 prefix exactly.
✗Configure 'router ospf 1' on R1 only, and use 'network 10.0.0.0 0.0.0.3 area 0' on R1; R2 does not need OSPF configuration because it will learn routes via the directly connected interface.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error is that OSPF is a dynamic routing protocol that must be enabled on both ends of a link for adjacency to form; one-sided configuration does not work.
Why candidates choose this
Candidates might think that because the link is directly connected, OSPF will automatically discover neighbors without explicit configuration on both sides.
✗Configure 'router ospf 1' on both routers, set router-id, and use 'network 10.0.0.0 255.255.255.252 area 0' on both routers.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error is confusing subnet masks with wildcard masks; OSPF uses inverse masks in network statements.
Why candidates choose this
Candidates often mistakenly use subnet masks instead of wildcard masks because they are more familiar with subnet masks from IP addressing.
✗Configure 'router ospf 1' on both routers, set router-id, and use 'network 10.0.0.0 0.0.0.0 area 0' on both routers.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error is using a host wildcard mask that does not cover the actual interface IPs; the correct wildcard mask must include the range of IPs on the link.
Why candidates choose this
Candidates might think that using a host mask (0.0.0.0) is sufficient because the network statement is for the network address, but OSPF matches the interface IP, not the network address.
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
Router
A router is a networking device that connects different networks together and directs data traffic between them by choosing the best path for data to travel.
Key term
Subnet
A subnet is a logical subdivision of an IP network, created by partitioning a larger network address space using subnet masks.
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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.