The answer is MP-BGP and MPLS labels, as these two components work together to deliver Layer 3 VPN services across a service provider network. MP-BGP is responsible for exchanging VPNv4 routes between Provider Edge routers, carrying both the route and its corresponding MPLS label, which ensures that customer routing information remains isolated. MPLS labels then forward packets across the provider core using label-switched paths, enabling efficient traffic separation without requiring the core routers to know the customer routes. On the Cisco SPCOR 350-501 exam, this question tests your understanding of the control plane versus data plane split: MP-BGP handles route distribution, while MPLS labels handle packet forwarding. A common trap is confusing MP-BGP with LDP or IGP—remember that only MP-BGP carries the VPNv4 address family with labels. Memory tip: think of MP-BGP as the “map maker” and MPLS labels as the “highway signs”—one tells you where to go, the other gets you there.
350-501 Networking Practice Question
This 350-501 practice question tests your understanding of networking. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Which TWO MPLS VPN features are used to provide Layer 3 VPN services in a service provider network?
Why wrong: LDP distributes labels for LSPs but is not specific to VPNs; it is used for any MPLS forwarding.
B
VRF
Why wrong: VRF is a configuration element to maintain per-VPN routing tables, but is not a protocol or feature that by itself provides the VPN service.
C
MPLS labels
MPLS labels are used to encapsulate and forward VPN traffic across the provider core.
D
RSVP-TE
Why wrong: RSVP-TE is used for traffic engineering, not for basic L3VPN operation.
E
MP-BGP
MP-BGP carries VPNv4 routes with route distinguishers and route targets to separate VPNs.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
MPLS labels
MP-BGP (Option E) is used to exchange VPNv4 routes between Provider Edge (PE) routers, carrying both the route and its corresponding MPLS label. MPLS labels (Option C) are used to forward packets across the provider core via label-switched paths (LSPs), enabling the separation of customer traffic. Together, MP-BGP and MPLS labels form the foundation of Layer 3 MPLS VPN services.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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
Why it's wrong here
LDP distributes labels for LSPs but is not specific to VPNs; it is used for any MPLS forwarding.
✗
VRF
Why it's wrong here
VRF is a configuration element to maintain per-VPN routing tables, but is not a protocol or feature that by itself provides the VPN service.
✓
MPLS labels
Why this is correct
MPLS labels are used to encapsulate and forward VPN traffic across the provider core.
Related concept
Read the scenario before looking for a memorised answer.
✗
RSVP-TE
Why it's wrong here
RSVP-TE is used for traffic engineering, not for basic L3VPN operation.
✓
MP-BGP
Why this is correct
MP-BGP carries VPNv4 routes with route distinguishers and route targets to separate VPNs.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between the control plane protocols (MP-BGP) and data plane mechanisms (MPLS labels) versus supporting protocols like LDP or RSVP-TE, leading candidates to mistakenly include LDP as a VPN service feature.
Detailed technical explanation
How to think about this question
In an MPLS Layer 3 VPN, MP-BGP (Multiprotocol BGP) uses the VPN-IPv4 address family (RFC 4364) to carry customer routes with a Route Distinguisher (RD) and Route Targets (RTs) for import/export control. The MPLS label assigned by the egress PE is carried as a BGP attribute (the MPLS label field in the NLRI), enabling label-switched forwarding across the provider core without examining the IP header. This dual mechanism ensures both reachability and traffic separation.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Networking — This question tests Networking — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: MPLS labels — MP-BGP (Option E) is used to exchange VPNv4 routes between Provider Edge (PE) routers, carrying both the route and its corresponding MPLS label. MPLS labels (Option C) are used to forward packets across the provider core via label-switched paths (LSPs), enabling the separation of customer traffic. Together, MP-BGP and MPLS labels form the foundation of Layer 3 MPLS VPN services.
What should I do if I get this 350-501 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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