Question 1,342 of 2,152

DMVPN →mediumMultiple ChoiceObjective-mapped

Quick Answer

The answer is that the spoke's EIGRP network statement does not include the loopback subnet. EIGRP only advertises networks that are explicitly matched by a network statement under the routing process, or that fall under a configured passive interface; without this statement, the loopback interface’s subnet is not injected into EIGRP updates, even though the neighbor relationship over the tunnel is established. On the Cisco CCNP ENARSI 300-410 exam, this scenario tests your understanding of how DMVPN phase 2 relies on proper EIGRP network advertisements for spoke-to-spoke communication, and a common trap is assuming that simply enabling EIGRP on the tunnel interface automatically advertises all connected subnets. Remember the memory tip: “No network, no route” — if a subnet isn’t listed under the EIGRP process, it stays silent, regardless of the neighbor state.

300-410 DMVPN Practice Question

This 300-410 practice question tests your understanding of dmvpn. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.

A network engineer is troubleshooting a DMVPN phase 2 network where the hub router is not learning the loopback interface routes from the spokes via EIGRP. The spokes have EIGRP configured on the tunnel interface and are advertising their loopback0 interface. The hub's EIGRP neighbor relationship with the spokes is established. However, the hub's routing table does not contain the loopback routes. The engineer checks the spoke's EIGRP configuration and sees that the loopback interface is not included in any network statement. What is the most likely cause?

Clue words in this question

Noticing these words before you look at the options changes how you read each choice.

Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.

Question 1mediummultiple choice

Study the full EIGRP explanation →

A
The spoke's EIGRP network statement does not include the loopback subnet.
Correct because EIGRP must have a network statement that matches the loopback subnet to advertise it.
B
The hub's EIGRP is configured with a distribute-list that filters the loopback routes.
Why wrong: Incorrect because the issue is on the spoke side; the hub is not receiving the routes.
C
The tunnel interface on the spoke has 'no ip split-horizon' configured.
Why wrong: Incorrect because split-horizon affects the hub's ability to advertise routes back to spokes, not the spoke's ability to advertise.
D
The loopback interface on the spoke is in a different VRF than the tunnel interface.
Why wrong: Incorrect because VRF mismatch would prevent EIGRP from learning the loopback, but the neighbor relationship is established.

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

✓

The spoke's EIGRP network statement does not include the loopback subnet.

EIGRP only advertises networks that are included in a network statement or configured under the EIGRP process. If the loopback interface is not included in a network statement, EIGRP will not advertise it.

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.

✓
The spoke's EIGRP network statement does not include the loopback subnet.
Why this is correct
Correct because EIGRP must have a network statement that matches the loopback subnet to advertise it.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
OSPF neighbours must agree on key parameters.
✗
The hub's EIGRP is configured with a distribute-list that filters the loopback routes.
Why it's wrong here
Incorrect because the issue is on the spoke side; the hub is not receiving the routes.
✗
The tunnel interface on the spoke has 'no ip split-horizon' configured.
Why it's wrong here
Incorrect because split-horizon affects the hub's ability to advertise routes back to spokes, not the spoke's ability to advertise.
✗
The loopback interface on the spoke is in a different VRF than the tunnel interface.
Why it's wrong here
Incorrect because VRF mismatch would prevent EIGRP from learning the loopback, but the neighbor relationship is established.

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?

DMVPN — This question tests DMVPN — OSPF neighbours must agree on key parameters..

What is the correct answer to this question?

The correct answer is: The spoke's EIGRP network statement does not include the loopback subnet. — EIGRP only advertises networks that are included in a network statement or configured under the EIGRP process. If the loopback interface is not included in a network statement, EIGRP will not advertise it.

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

Are there clue words in this question I should notice?

Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.

What is the key concept behind this question?

OSPF neighbours must agree on key parameters.

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