300-410 Infrastructure Services Practice Question
A network engineer is troubleshooting an MPLS L3 VPN where OSPF is used as the PE-CE routing protocol. The customer reports that routes from one site are not being learned at another site. The engineer checks the PE routers and finds that the OSPF routes are present in the VRF routing table but not in the MP-BGP table. What is the most likely cause?
⚠ Common exam trap
The trap here is assuming a route target or VRF misconfiguration when the routes are missing from MP-BGP; the first step is to check redistribution into BGP.
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 OSPF routes are not being redistributed into BGP.
When OSPF routes are present in the VRF routing table but not in MP-BGP, the most likely cause is that redistribution from OSPF into BGP is not configured. MP-BGP only advertises routes that are explicitly redistributed or network statements are used. Without redistribution, the routes remain local to the VRF and are not propagated as VPNv4 routes. Other issues like route target or VRF configuration would manifest differently.
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 configuration is incorrect.
Why it's wrong here
If the route target were incorrect, the routes might not be imported into the remote VRF, but they would still appear in the local MP-BGP table if redistribution is configured. The issue described is that routes are missing from MP-BGP entirely, indicating a redistribution problem, not a route target mismatch.
- ✗
The OSPF process is not configured with the correct VRF.
Why it's wrong here
If the OSPF process were not associated with the correct VRF, the routes would not appear in the VRF routing table at all. Since the routes are present in the VRF routing table, the OSPF process is correctly associated. The problem is the next step: getting them into BGP.
- ✓
The OSPF routes are not being redistributed into BGP.
Why this is correct
For OSPF routes from a VRF to be advertised across the MPLS VPN to other PEs, they must be redistributed into MP-BGP. If redistribution is not configured, the routes remain only in the VRF routing table and are not exported as VPNv4 routes. This is the most likely cause when routes are present in the VRF but missing from MP-BGP.
- ✗
The BGP router ID is not unique.
Why it's wrong here
A duplicate BGP router ID can cause session issues, but it would not prevent redistribution of OSPF routes into BGP. If the BGP session were down, the routes would not be advertised, but the local MP-BGP table might still show them if redistribution is configured. The missing routes in MP-BGP point to redistribution as the cause.
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
VRF-Lite and Multi-Protocol BGP
Key term
MP-BGP for VPN
MP-BGP for VPN is an extension of the Border Gateway Protocol that carries multiple types of network layer information to enable scalable, isolated virtual private networks over a shared provider infrastructure.
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.