hardMultiple ChoiceObjective-mapped
300-410 An enterprise uses VRF-lite with IPv6 Practice Question
An enterprise uses VRF-lite with IPv6. VRF A on R1 leaks routes to VRF B using route-target import/export. R1 has an IPv6 ACL applied inbound on the interface in VRF A that permits only OSPFv3 and denies all other traffic. R1's VRF B has a static default route pointing to a next-hop in VRF A. Traffic from VRF B to the internet fails. R1 shows 'ping vrf B 2001:db8:2::1' fails, but 'ping vrf A 2001:db8:2::1' succeeds. What is the root cause?
⚠ Common exam trap
Cisco often tests the misconception that route leaking bypasses interface ACLs, when in fact ACLs are applied to the data plane traffic that uses the leaked routes, not just to the routing protocol updates.
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 ACL on the VRF A interface blocks data traffic from VRF B, which is forwarded via the leaked route.
The ACL on the VRF A interface is configured to permit only OSPFv3 (IPv6 routing protocol traffic) and deny all other traffic. When VRF B leaks routes to VRF A, data traffic from VRF B destined to the internet is forwarded via the leaked route and enters the VRF A interface. This data traffic is not OSPFv3, so it is denied by the ACL, causing the ping to fail. The ping from VRF A succeeds because it originates within VRF A and does not traverse the ACL inbound on the same interface.
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 ACL on the VRF A interface blocks data traffic from VRF B, which is forwarded via the leaked route.
Why this is correct
Traffic from VRF B is forwarded into VRF A and hits the inbound ACL, which permits only OSPFv3.
- ✗
Route leaking is not configured correctly; the route-target import/export is missing.
Why it's wrong here
If leaking were broken, the ping from VRF A would also fail.
- ✗
The static default route in VRF B has an incorrect next-hop address.
Why it's wrong here
If the next-hop were wrong, the ping from VRF A would also fail.
- ✗
uRPF is enabled on the VRF A interface and drops traffic from VRF B due to source address mismatch.
Why it's wrong here
uRPF is not mentioned in the configuration; the ACL is the issue.
Visual reference
Quick reference
Routing Protocol Comparison
| Protocol | Metric | Max Hops | Algorithm | Type |
|---|---|---|---|---|
| RIP v2 | Hop count | 15 | Bellman-Ford | Distance vector |
| OSPF | Cost (bandwidth) | Unlimited | Dijkstra (SPF) | Link state |
| EIGRP | Composite metric | Unlimited | DUAL | Hybrid |
| IS-IS | Cost | Unlimited | Dijkstra | Link state |
| BGP | Policy / attributes | Unlimited | Path vector | Path vector |
RIP's 15-hop limit makes it unsuitable for large networks. OSPF and EIGRP dominate modern enterprise deployments.
Go deeper
Related to this question
Learn chapter
OSPF Route Summarization and Filtering
Key term
MPLS Layer 3 VPN
A technology that uses Multiprotocol Label Switching to create secure, scalable virtual private networks that connect multiple sites at the network layer, where the service provider manages routing between customer sites.
Key term
IPv6 Next Hop Resolution
IPv6 Next Hop Resolution is the process a router uses to determine the next router or destination device to which a packet should be forwarded, based on the destination IPv6 address and the routing table.
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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.