Question 1,218 of 2,152
Device Access ControlhardMultiple ChoiceObjective-mapped

VRF Route Leaking: Why Next-Hop Becomes Unreachable in Destination VRF

This 300-410 practice question tests your understanding of device access control. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. A key principle to apply: route-replicate. 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 VRF-aware network has two VRFs: VRF A and VRF B. Router R1 is configured with VRF A and VRF B, and route leaking is configured between them using route-replicate. Routes from VRF A are appearing in VRF B, but traffic from VRF B to destinations in VRF A is failing. R1's configuration: ip route vrf A 10.10.10.0 255.255.255.0 192.168.1.1, and route-replicate from VRF A to VRF B. Show ip route vrf B shows the route 10.10.10.0/24 with next-hop 192.168.1.1. However, ping from a device in VRF B to 10.10.10.1 fails. What is the root cause?

Quick Answer

The answer is that the next-hop remains in the source VRF after route leaking, causing a VRF mismatch that drops the packet. When route-replicate copies a route from VRF A to VRF B, it duplicates the prefix and its next-hop address without altering the next-hop’s VRF association. In this scenario, the next-hop 192.168.1.1 is reachable only within VRF A’s routing table, but VRF B attempts a recursive lookup for that address in its own table, where it does not exist—resulting in a CEF adjacency failure and an unreachable next-hop. On the Cisco CCNP ENARSI 300-410 exam, this question tests your understanding that route leaking is a control-plane operation; it does not install the next-hop’s path into the destination VRF. A common trap is assuming the leaked route is fully functional, but the forwarding plane still requires the next-hop to be present in the destination VRF. Remember the memory tip: “Leak the route, not the next-hop”—the prefix moves, but the gateway stays home.

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 next-hop 192.168.1.1 is not reachable in VRF B because it belongs to VRF A; route leaking does not update the next-hop, causing recursive routing failure.

The correct answer is A. Route-replicate copies routes from VRF A to VRF B but does not change the next-hop address. The next-hop 192.168.1.1 remains in VRF A's routing table and is not reachable within VRF B. When VRF B attempts to forward traffic to 10.10.10.0/24, the recursive lookup for 192.168.1.1 fails because that next-hop is not present in VRF B's routing table, causing the ping to fail. Option D is incorrect because the packet is dropped due to the recursive routing failure, not specifically because the interface is not in VRF B; the interface may be in VRF A and reachable from VRF B's perspective only if the next-hop is resolved, but it is not.

Key principle: route-replicate

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 next-hop 192.168.1.1 is not reachable in VRF B because it belongs to VRF A; route leaking does not update the next-hop, causing recursive routing failure.

    Why this is correct

    The route is installed but the next-hop is not in VRF B, so the packet cannot be forwarded.

    Related concept

    route-replicate

  • The route-replicate command requires a route-map to change the next-hop.

    Why it's wrong here

    Route-replicate does not have an option to change next-hop; it copies the route as-is.

  • The VRF B has a default route that is conflicting with the leaked route.

    Why it's wrong here

    A default route would not cause failure to reach the specific prefix; it might even help if the next-hop is reachable.

  • The interface connected to 192.168.1.1 is not in VRF B, so the packet is dropped by CEF due to VRF mismatch.

    Why this is correct

    This is essentially the same as option A; the next-hop is not in the same VRF, so forwarding fails.

    Related concept

    route-replicate

Common exam traps

Common exam trap: answer the scenario, not the keyword

Candidates often assume that route-leaking automatically adjusts the next-hop or that the next-hop becomes reachable in the destination VRF. In reality, the next-hop remains unchanged and must be reachable in the destination VRF for traffic to succeed. This is a classic recursive routing failure scenario.

Detailed technical explanation

How to think about this question

Route-replicate (or import/export via route-target) copies the route prefix but preserves the original next-hop address. If that next-hop belongs to a different VRF, the receiving VRF must have a route to reach that next-hop, or recursive routing fails. In production, this is often solved by using a route-map to set the next-hop to a loopback or interface that exists in both VRFs, or by ensuring the next-hop is reachable via a global or shared VRF route.

KKey Concepts to Remember

  • route-replicate
  • Recursive routing
  • VRF-aware routing

TExam Day Tips

  • Watch for words such as best, first, most likely and least administrative effort.
  • Review why wrong options are wrong, not only why the correct option is correct.

Key takeaway

route-replicate

Real-world example

How this comes up in practice

A practitioner preparing for the 300-410 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. route-replicate Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.

Visual reference

Client Recursive Resolver Root DNS (13 root servers) TLD DNS (.com, .org, …) Authoritative example.com query IP addr answer

What to study next

Got this wrong? Here's your next step.

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FAQ

Questions learners often ask

What does this 300-410 question test?

Device Access Control — This question tests Device Access Control — route-replicate.

What is the correct answer to this question?

The correct answer is: The next-hop 192.168.1.1 is not reachable in VRF B because it belongs to VRF A; route leaking does not update the next-hop, causing recursive routing failure. — The correct answer is A. Route-replicate copies routes from VRF A to VRF B but does not change the next-hop address. The next-hop 192.168.1.1 remains in VRF A's routing table and is not reachable within VRF B. When VRF B attempts to forward traffic to 10.10.10.0/24, the recursive lookup for 192.168.1.1 fails because that next-hop is not present in VRF B's routing table, causing the ping to fail. Option D is incorrect because the packet is dropped due to the recursive routing failure, not specifically because the interface is not in VRF B; the interface may be in VRF A and reachable from VRF B's perspective only if the next-hop is resolved, but it is not.

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

Review route-replicate, then practise related 300-410 questions on the same topic to reinforce the concept.

What is the key concept behind this question?

route-replicate

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Last reviewed: Jun 24, 2026

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