- A
Customer edge (CE) routers exchange routing information with provider edge (PE) routers using static routing, RIP, OSPF, EIGRP, or BGP.
Correct because PE-CE routing can use any of these protocols, as supported by the provider's configuration.
- B
VRF (Virtual Routing and Forwarding) instances are used on PE routers to maintain separate routing tables for each VPN customer.
Correct because VRFs isolate customer routes on the PE, ensuring traffic separation.
- C
MP-BGP (Multiprotocol BGP) is used between PE routers to exchange VPNv4 routes, which include an RD and RT.
Correct because MP-BGP carries VPN-IPv4 prefixes with route distinguishers (RD) and route targets (RT) for VPN membership.
- D
The MPLS core routers (P routers) maintain full VPN routing tables to forward traffic based on customer IP prefixes.
Why wrong: Incorrect because P routers only swap MPLS labels and do not maintain VPN routing tables; they are label-switching routers.
- E
Route targets (RT) are used to uniquely identify each customer VPN across the provider network.
Why wrong: Incorrect because route distinguishers (RD) ensure uniqueness of VPN prefixes, while RTs control route import/export policies.
Quick Answer
The answer is that MP-BGP is used between PE routers to exchange VPNv4 routes, which include an RD and RT. This is correct because MPLS Layer 3 VPNs rely on Virtual Routing and Forwarding (VRF) instances to keep customer routing tables isolated on the Provider Edge (PE) router, while Multiprotocol BGP (MP-BGP) carries the VPNv4 routes—prefixed with a Route Distinguisher (RD) for uniqueness and tagged with Route Targets (RT) for import/export control—across the MPLS core. The core routers (P routers) remain completely unaware of customer routes, simply swapping MPLS labels for forwarding. On the ENCOR 350-401 exam, this concept tests your understanding of control plane versus data plane separation in service provider architectures; a common trap is confusing RT with RD or thinking BGP runs on P routers. Remember the mnemonic: “PEs talk BGP, P’s just swap labels—VRFs isolate, RDs make unique, RTs control sharing.”
350-401 VPN Technologies Practice Question
This 350-401 practice question tests your understanding of vpn technologies. 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 three statements about MPLS Layer 3 VPNs are true? (Choose three.)
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
Customer edge (CE) routers exchange routing information with provider edge (PE) routers using static routing, RIP, OSPF, EIGRP, or BGP.
MPLS L3VPNs use VRFs for isolation, MP-BGP for route exchange, and MPLS labels for forwarding, with the provider core unaware of customer routes.
Key principle: OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Customer edge (CE) routers exchange routing information with provider edge (PE) routers using static routing, RIP, OSPF, EIGRP, or BGP.
Why this is correct
Correct because PE-CE routing can use any of these protocols, as supported by the provider's configuration.
Related concept
OSPF neighbours must agree on key parameters.
- ✓
VRF (Virtual Routing and Forwarding) instances are used on PE routers to maintain separate routing tables for each VPN customer.
Why this is correct
Correct because VRFs isolate customer routes on the PE, ensuring traffic separation.
Related concept
OSPF neighbours must agree on key parameters.
- ✓
MP-BGP (Multiprotocol BGP) is used between PE routers to exchange VPNv4 routes, which include an RD and RT.
- ✗
The MPLS core routers (P routers) maintain full VPN routing tables to forward traffic based on customer IP prefixes.
Why it's wrong here
Incorrect because P routers only swap MPLS labels and do not maintain VPN routing tables; they are label-switching routers.
- ✗
Route targets (RT) are used to uniquely identify each customer VPN across the provider network.
Why it's wrong here
Incorrect because route distinguishers (RD) ensure uniqueness of VPN prefixes, while RTs control route import/export policies.
Common exam traps
Common exam trap: OSPF can fail even when IP connectivity looks correct
OSPF neighbour formation depends on matching areas, timers, network type, authentication and passive-interface behaviour. Do not choose an answer only because the devices can ping.
Detailed technical explanation
How to think about this question
OSPF questions usually test the details that control adjacency and route selection. Read the neighbour state, area, router ID and interface configuration before deciding what is wrong.
KKey Concepts to Remember
- OSPF neighbours must agree on key parameters.
- Router ID selection can affect neighbour relationships and LSDB output.
- OSPF cost influences the preferred path.
- A route can appear in OSPF information but not become the installed route.
TExam Day Tips
- Check area mismatch first when OSPF adjacency fails.
- Review passive interfaces when a network is advertised but no neighbour forms.
- Use show ip ospf neighbor and show ip route clues carefully.
Key takeaway
OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
Real-world example
How this comes up in practice
A network engineer at a university connects two campus buildings via a fibre link. Both routers run OSPF, but no adjacency forms — even though both routers can ping each other. The engineer finds one router is in area 0 and the other in area 1. OSPF adjacency requires matching area numbers, hello/dead timers, and network type. IP reachability alone is not enough.
What to study next
Got this wrong? Here's your next step.
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related 350-401 OSPF questions on adjacency and route selection.
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FAQ
Questions learners often ask
What does this 350-401 question test?
VPN Technologies — This question tests VPN Technologies — OSPF neighbours must agree on key parameters..
What is the correct answer to this question?
The correct answer is: Customer edge (CE) routers exchange routing information with provider edge (PE) routers using static routing, RIP, OSPF, EIGRP, or BGP. — MPLS L3VPNs use VRFs for isolation, MP-BGP for route exchange, and MPLS labels for forwarding, with the provider core unaware of customer routes.
What should I do if I get this 350-401 question wrong?
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related 350-401 OSPF questions on adjacency and route selection.
What is the key concept behind this question?
OSPF neighbours must agree on key parameters.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Same concept, more angles
1 more ways this is tested on 350-401
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. Which three statements about MPLS Layer 3 VPNs are true? (Choose three.)
hard- ✓ A.MP-BGP is used to exchange VPNv4 routes between PE routers.
- ✓ B.Each customer site requires a separate VRF on the PE router.
- C.The P router maintains a full routing table for all VPN customers.
- D.A single MPLS label is used for both transport and VPN identification.
- ✓ E.The PE router performs the routing between the CE device and the MPLS core.
Why A: MPLS L3VPNs use MP-BGP to exchange VPNv4 routes, require a VRF per customer, and use two labels (IGP label for transport, VPN label for VRF lookup). The PE router performs the routing between CE and the MPLS core.
Keep practising
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Last reviewed: Jun 18, 2026
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