The correct configuration to establish an OSPFv2 single-area adjacency in area 0 is to enter router ospf 1 on both R1 and R2, set a unique router-id, and apply the network 10.0.0.0 0.0.0.3 area 0 command under the OSPF process. This works because OSPF forms an adjacency only when both routers share a common subnet and area; the wildcard mask 0.0.0.3 matches the exact 10.0.0.0/30 link, ensuring the interfaces on that segment become active in area 0. On the CCNA 200-301 v2 exam, this task tests your ability to configure and verify a fundamental OSPF adjacency, a core routing concept that often appears in both simulation and multiple-choice questions. A common trap is confusing the wildcard mask with a subnet mask—using 255.255.255.252 instead of 0.0.0.3 will fail to enable OSPF on the interface. For a quick memory tip, remember that OSPF wildcards are the inverse of the subnet mask: a /30 subnet (255.255.255.252) becomes 0.0.0.3, and you always pair it with the network address, not the interface IP.
CCNA IP Routing Practice Question
This 200-301 practice question tests your understanding of ip routing. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. 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.
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.
R1#show ip interface brief
Interface IP-Address OK? Method Status Protocol
GigabitEthernet0/0 10.0.0.1 YES manual up up
GigabitEthernet0/1 192.168.1.1 YES manual up up
Loopback0 10.1.1.1 YES manual up up
R1#show running-config | section interface
interface GigabitEthernet0/0
ip address 10.0.0.1 255.255.255.252
no shutdown
!
interface GigabitEthernet0/1
ip address 192.168.1.1 255.255.255.0
no shutdown
!
interface Loopback0
ip address 10.1.1.1 255.255.255.255
A
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.
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.
B
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 wrong: This is incorrect because OSPF requires both routers to be configured with OSPF and to have matching parameters to form an adjacency. R2 must also run OSPF and advertise the link.
C
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 wrong: This is incorrect because OSPF network statements use a wildcard mask, not a subnet mask. The correct wildcard mask for a /30 prefix is 0.0.0.3, not 255.255.255.252.
D
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 wrong: 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.
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).
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.
✓
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 is incorrect because OSPF requires both routers to be configured with OSPF and to have matching parameters to form an adjacency. R2 must also run OSPF and advertise the link.
✗
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
This is incorrect because OSPF network statements use a wildcard mask, not a subnet mask. The correct wildcard mask for a /30 prefix is 0.0.0.3, not 255.255.255.252.
✗
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?”
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.
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 200-301 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 200-301 OSPF questions on adjacency and route selection.
IP Routing — This question tests IP Routing — OSPF neighbours must agree on key parameters..
What is the correct answer to this question?
The correct answer is: 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).
What should I do if I get this 200-301 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 200-301 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. Match each OSPF adjacency requirement or concept to its most accurate description.
medium
✓ A.Neighbor discovery uses Hello packets to establish and maintain adjacencies.
B.DR/BDR election reduces the number of LSAs flooded in a broadcast multiaccess network.
C.LSA flooding is the process by which OSPF routers exchange link-state information to build a common topology database.
D.The SPF algorithm is used to compute the shortest path to each destination based on the link-state database.
Why A: Hello/Dead timers must match between neighbors to form a stable OSPF adjacency; mismatched timers cause neighbor relationships to fail. Area must be identical on the shared OSPF segment because routers in different areas do not establish full adjacencies. Router ID uniquely identifies the router within the OSPF process, used for DR/BDR election and LSA origination. Passive interface suppresses hello packets, preventing neighbor formation on that link, while still allowing the connected network to be advertised via the router's LSA.
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