hardMultiple ChoiceObjective-mapped
300-410 Practice Question: Router R1 is configured for VRF-Lite with MPLS
Router R1 is configured for VRF-Lite with MPLS. The interface Gig0/0 is in VRF-A and is running LDP. The LDP neighbor with R2 is not establishing. R1 configuration: mpls ip, mpls label protocol ldp, interface Gig0/0, ip vrf forwarding VRF-A, ip address 10.0.0.1 255.255.255.252. R2 has similar configuration without VRF. The LDP hello packets are sent but not received. 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
✓
LDP cannot form a session between a VRF interface and a global interface; both must be in the same VRF or both in the global table.
LDP uses UDP and TCP, and the transport address is typically the router ID. In a VRF, the LDP session must be established within the same VRF. If R1 has VRF-A and R2 does not, the LDP hellos are sent in the VRF context, but R2's LDP process is in the global table. The hellos are not recognized because the VRF label space is different. LDP requires matching VRF or global configuration.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
LDP cannot form a session between a VRF interface and a global interface; both must be in the same VRF or both in the global table.
Why this is correct
Correct: LDP sessions require matching VRF context; mismatch prevents session establishment.
- ✗
The MPLS label protocol must be TDP on both sides.
Why it's wrong here
Incorrect: LDP is standard; TDP is deprecated.
- ✗
The interface IP addresses must be in the same subnet.
Why it's wrong here
Incorrect: They are in the same subnet; the issue is VRF mismatch.
- ✗
The mpls ip command must be applied under the VRF address-family.
Why it's wrong here
Incorrect: The command is applied on the interface; VRF address-family is for routing protocols.
Go deeper
Related to this question
Learn chapter
OSPF Neighbor Adjacency and Basics
Key term
MPLS Label Distribution
MPLS Label Distribution is the process by which routers exchange labels that tell them how to forward packets across a network without looking at the IP address each time.
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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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.