Question 174 of 2,152

OSPF Troubleshooting (v2/v3) →mediumMultiple ChoiceObjective-mapped

Quick Answer

The correct answer is that the OSPF network statement for multiple areas enables OSPF on all interfaces whose IP addresses fall within the specified ranges and assigns them to the corresponding areas. This works because the network statement uses a wildcard mask to match interface IPs, not subnets; the first statement matches any interface with an IP in the 10.0.0.0/8 range and places it in area 0, while the second matches 192.168.1.0/24 interfaces into area 1. On the Cisco CCNP ENARSI 300-410 exam, this configuration tests your understanding of how OSPF network statements operate under the traditional interface-based OSPF model, and a common trap is confusing the wildcard mask with a subnet mask—here, 0.255.255.255 matches all 10.x.x.x addresses, not just a single /8. A helpful memory tip is to think of the wildcard mask as an "inverse subnet mask": zeros mean "must match exactly," and 255s mean "ignore those bits," so 0.255.255.255 forces the first octet to be 10 while allowing any value in the remaining three octets.

300-410 OSPF Troubleshooting (v2/v3) Practice Question

This 300-410 practice question tests your understanding of ospf troubleshooting (v2/v3). This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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.

Examine the following OSPF configuration on router R1:

router ospf 1
 network 10.0.0.0 0.255.255.255 area 0
 network 192.168.1.0 0.0.0.255 area 1

What is the effect of this configuration?

Question 1mediummultiple choice

Review the full OSPF breakdown →

A
All interfaces with IP addresses in the 10.0.0.0/8 range will be enabled for OSPF in area 0, and interfaces in 192.168.1.0/24 will be in area 1.
Correct. The wildcard mask 0.255.255.255 matches the first octet, and 0.0.0.255 matches the last octet.
B
Only the interface with IP 10.0.0.1 will be in area 0; all other 10.x.x.x interfaces are ignored.
Why wrong: Incorrect. The wildcard mask 0.255.255.255 matches all addresses starting with 10.
C
The configuration is invalid because OSPF process 1 cannot have two network statements in different areas.
Why wrong: Incorrect. OSPF can have multiple network statements in different areas.
D
The configuration will cause a routing loop between area 0 and area 1.
Why wrong: Incorrect. There is no loop; area 0 is the backbone, and area 1 is a regular area.

Full breakdown with real-world context →

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

✓

All interfaces with IP addresses in the 10.0.0.0/8 range will be enabled for OSPF in area 0, and interfaces in 192.168.1.0/24 will be in area 1.

The network statements define which interfaces participate in OSPF and assign them to areas. The first statement covers all interfaces with IP addresses starting with 10.x.x.x, and the second covers 192.168.1.x. This is a valid configuration.

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.

✓
All interfaces with IP addresses in the 10.0.0.0/8 range will be enabled for OSPF in area 0, and interfaces in 192.168.1.0/24 will be in area 1.
Why this is correct
Correct. The wildcard mask 0.255.255.255 matches the first octet, and 0.0.0.255 matches the last octet.
Related concept
OSPF neighbours must agree on key parameters.
✗
Only the interface with IP 10.0.0.1 will be in area 0; all other 10.x.x.x interfaces are ignored.
Why it's wrong here
Incorrect. The wildcard mask 0.255.255.255 matches all addresses starting with 10.
✗
The configuration is invalid because OSPF process 1 cannot have two network statements in different areas.
Why it's wrong here
Incorrect. OSPF can have multiple network statements in different areas.
✗
The configuration will cause a routing loop between area 0 and area 1.
Why it's wrong here
Incorrect. There is no loop; area 0 is the backbone, and area 1 is a regular area.

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.

What to study next

Got this wrong? Here's your next step.

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 300-410 OSPF questions on adjacency and route selection.

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FAQ

Questions learners often ask

What does this 300-410 question test?

OSPF Troubleshooting (v2/v3) — This question tests OSPF Troubleshooting (v2/v3) — OSPF neighbours must agree on key parameters..

What is the correct answer to this question?

The correct answer is: All interfaces with IP addresses in the 10.0.0.0/8 range will be enabled for OSPF in area 0, and interfaces in 192.168.1.0/24 will be in area 1. — The network statements define which interfaces participate in OSPF and assign them to areas. The first statement covers all interfaces with IP addresses starting with 10.x.x.x, and the second covers 192.168.1.x. This is a valid configuration.

What should I do if I get this 300-410 question wrong?

What is the key concept behind this question?

OSPF neighbours must agree on key parameters.

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