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300-410 Practice Question: A large enterprise network is experiencing…

A large enterprise network is experiencing intermittent reachability between VRF-A on Router R1 and VRF-B on Router R2. R1 has the following relevant configuration: ip vrf VRF-A, rd 100:1, route-target export 100:1, route-target import 100:2. R2 shows: ip vrf VRF-B, rd 200:2, route-target export 200:2, route-target import 200:1. The link between R1 and R2 is configured with VRF forwarding VRF-A on R1 and VRF forwarding VRF-B on R2. What is the root cause?

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 route-target import and export values are mismatched between the VRFs, preventing route exchange.

The route-target import/export values are mismatched for the VRF-Lite scenario. In VRF-Lite, route-targets are used for route leaking, but on a direct link, the VRFs must match or route leaking must be configured properly. Here, R1 imports routes with RT 100:2, which R2 exports as 200:2, not 100:2. R2 imports RT 200:1, but R1 exports 100:1. Thus, no routes are exchanged, causing unreachability.

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 route-target import and export values are mismatched between the VRFs, preventing route exchange.

    Why this is correct

    Correct: R1 exports RT 100:1, but R2 imports RT 200:1; R2 exports RT 200:2, but R1 imports RT 100:2. No common RT exists.

  • ✗

    The RD values must match for VRF-Lite to work on a direct link.

    Why it's wrong here

    Incorrect: RD values do not need to match; they are used for route distinguishment, not for route exchange.

  • ✗

    The VRFs must have the same name on both routers for direct connectivity.

    Why it's wrong here

    Incorrect: VRF names are local and can differ; connectivity depends on route-target matching.

  • ✗

    The interface must be in the same VRF on both ends; route-targets are irrelevant for VRF-Lite.

    Why it's wrong here

    Incorrect: In VRF-Lite, route-targets are used for route leaking; if VRFs differ, route-targets must be configured correctly.

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Same concept, more angles

1 more way this is tested on 300-410

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. A network engineer is troubleshooting a VRF-Lite configuration on a Cisco router. The router has two VRFs (VRF_CUSTOMER_A and VRF_CUSTOMER_B). The engineer notices that traffic from VRF_CUSTOMER_A is being routed to the wrong next-hop, causing connectivity issues. The 'show ip route vrf VRF_CUSTOMER_A' shows a route to the destination via a next-hop that belongs to VRF_CUSTOMER_B. What is the most likely cause?

hard
  • ✓ A.The 'route-target import' command in VRF_CUSTOMER_A is importing routes from VRF_CUSTOMER_B.
  • B.The router has a default route that points to the next-hop in VRF_CUSTOMER_B.
  • C.The 'ip cef' command is disabled globally.
  • D.The 'ip vrf forwarding' command is applied to the same physical interface for both VRFs.

Why A: This issue is typically caused by route leaking between VRFs, which can happen if the route-target import/export commands are misconfigured or if there is a shared interface with incorrect VRF assignment.

JA

Written by Johnson Ajibi, MSc IT Security

Senior Network & Security Engineer · founder of Courseiva

This 300-410 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 300-410 exam.