300-410 Infrastructure Services Practice Question
A network engineer is configuring an MPLS L3VPN. The PE router is running OSPF with the CE router in VRF CUSTOMER. The engineer notices that routes from the customer are being redistributed into the provider's global OSPF process, causing instability. Which configuration change on the PE router will prevent this redistribution while still allowing customer routes to be advertised across the MPLS core?
⚠ Common exam trap
The trap here is thinking that filtering with distribute-list or changing domain-id solves the problem, but the actual fix is to remove the incorrect redistribution into the global OSPF process.
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
✓
Remove the redistribution of the VRF OSPF into the global OSPF process.
The root cause is the redistribution of the VRF OSPF into the provider's global OSPF. Removing that redistribution prevents customer routes from entering the provider's IGP, while MP-BGP can still carry the customer routes across the MPLS core as VPNv4 prefixes. This maintains customer connectivity without affecting the provider's routing stability.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Configure a distribute-list to filter the customer routes from being redistributed.
Why it's wrong here
A distribute-list can filter routes from being redistributed, but it is a less clean solution than simply removing the redistribution. Moreover, distribute-lists can be complex and may inadvertently filter other routes. The fundamental issue is the redistribution command itself; removing it is the direct fix.
- ✗
Configure the OSPF process with the capability vrf-lite command.
Why it's wrong here
The capability vrf-lite command is used to allow the PE to accept routes with the DN bit set when running OSPF in both global and VRF contexts. It does not prevent redistribution into the global OSPF; it actually facilitates the coexistence of OSPF processes. It is not the solution for preventing unwanted redistribution.
- ✗
Change the OSPF domain-id to a unique value.
Why it's wrong here
The domain-id is used in MP-BGP to identify the OSPF domain and prevent loops when redistributing back into OSPF. Changing it does not stop redistribution into the provider's global OSPF. The redistribution into global OSPF is a separate configuration that must be removed or filtered.
- ✓
Remove the redistribution of the VRF OSPF into the global OSPF process.
Why this is correct
The instability is caused by redistributing the customer's OSPF routes into the provider's global OSPF. Removing this redistribution stops the customer routes from entering the provider's IGP. The customer routes can still be advertised across the MPLS core by redistributing them into MP-BGP, which is the correct method for L3VPN route propagation.
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
ACL-Based Traffic Filtering and Policy-Based Routing
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
LDP Protocol
LDP, or Label Distribution Protocol, is a protocol that routers use to automatically exchange labels that enable MPLS (Multiprotocol Label Switching) to create fast, efficient paths for data packets across a network.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Cisco exam blueprint
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.