Quick Answer
The answer is BGP, specifically eBGP, as the typical CE-PE routing protocol in an MPLS L3VPN deployment. While the CE-PE routing protocol can technically be any option—including static, RIP, EIGRP, OSPF, or BGP—service providers overwhelmingly choose BGP for its scalability, support for multi-homing, and ability to carry multiple VPN routes without redistribution complexity. On the Cisco SPCOR / CCNP Service Provider Core 350-501 exam, this question tests your understanding that “typical” implies the most common production choice, not the only possible one; a common trap is assuming OSPF is always preferred because it is widely used in enterprise networks. Remember that in MPLS L3VPN, the PE router must separate customer routes using VRFs, and BGP’s route-target and route-distinguisher mechanisms integrate seamlessly with this architecture. A useful memory tip: “BGP is the glue between CE and PE for scalable VPNs.”
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 routing protocol is used between CE and PE routers in a typical MPLS L3VPN deployment?
RIP
Why wrong: RIP is possible but outdated; not typical for modern SP networks.
BGP
eBGP is commonly used for CE-PE routing in L3VPN to carry customer routes and support multi-homing.
EIGRP
Why wrong: EIGRP is Cisco proprietary and less common in multi-vendor SP environments.
IS-IS
Why wrong: IS-IS is typically used within the provider core, not between CE and PE.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
BGP
The CE-PE routing protocol can be any: static, RIP, EIGRP, OSPF, or BGP. However, in service provider networks, eBGP or OSPF are common. The question asks for typical; BGP is often used for multi-homing and scalability.
Key principle: OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Common exam traps
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
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.
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
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
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 350-501 OSPF questions on adjacency and route selection.
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FAQ
Networking — This question tests Networking — OSPF neighbours must agree on key parameters..
The correct answer is: BGP — The CE-PE routing protocol can be any: static, RIP, EIGRP, OSPF, or BGP. However, in service provider networks, eBGP or OSPF are common. The question asks for typical; BGP is often used for multi-homing and scalability.
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 350-501 OSPF questions on adjacency and route selection.
OSPF neighbours must agree on key parameters.
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Last reviewed: Jun 24, 2026
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.
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