350-501 Services Practice Question
A customer's MPLS L3VPN has two CE routers connected to two different PEs, but the PEs are not receiving the customer's routes from each other. The PE-CE routing protocol is OSPF. The PEs have the VRF configured with OSPF process, and the routes from CE are in the VRF routing table. The MP-BGP session between PEs is up and the VPNv4 address family is working. On the source PE, the routes show as not advertised to BGP. What is the likely issue?
⚠ Common exam trap
Cisco often tests the misconception that simply enabling OSPF under a VRF and having a working MP-BGP session is sufficient for route exchange, when in fact explicit redistribution from OSPF into BGP VPNv4 is required.
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 process on the PE is not redistributed into BGP VPNv4 under the VRF
In an MPLS L3VPN with OSPF as the PE-CE protocol, the VRF OSPF process must be explicitly redistributed into the MP-BGP VPNv4 address family using the `redistribute ospf <process-id> match internal external` command under the VRF address-family IPv4. Without this redistribution, the OSPF routes learned from the CE remain in the VRF routing table but are never injected into BGP, so they are not advertised to the remote PE, even though the MP-BGP session is up and the VPNv4 address family is working.
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 export on the source PE does not match the import on the remote PE
Why it's wrong here
Incorrect. If route-target mismatched, routes would be advertised but not imported by the remote PE.
- ✗
The OSPF network type is not set to broadcast
Why it's wrong here
Incorrect. OSPF network type does not affect redistribution into BGP.
- ✓
The OSPF process on the PE is not redistributed into BGP VPNv4 under the VRF
Why this is correct
Correct. The 'redistribute ospf process-id' command under the VRF address-family is missing, so OSPF routes are not injected into MP-BGP.
- ✗
The next-hop-self is not configured under the VRF OSPF process
Why it's wrong here
Incorrect. Next-hop-self is used for BGP advertisement to other PEs; it does not affect route advertisement from OSPF to BGP.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 350-501 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 350-501 exam.