The answer is that the neighbor 10.1.1.1 is not configured under the address-family ipv4 vrf CUSTOMER. This is because BGP neighbor activation under VRF requires the neighbor statement to be explicitly placed within the VRF-specific address-family, not just under the global IPv4 unicast address-family; without this, the PE router receives the eBGP default route but does not install it into the VRF routing table. On the Cisco SPCOR and CCNP Service Provider Core 350-501 exam, this scenario tests your understanding of how BGP multiprotocol extensions isolate routing information per VRF, and a common trap is assuming that a globally configured neighbor automatically applies to all VRFs. A reliable memory tip is "activate where you import"—the neighbor must be activated inside the same address-family block where the VRF is defined for the route to be placed into the VRF table.
350-501 Services Practice Question
This 350-501 practice question tests your understanding of services. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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.
Refer to the exhibit. A PE router has this BGP configuration. The CE router is advertising a default route via eBGP. However, the PE is not installing the route in the VRF table. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The neighbor 10.1.1.1 is not configured under the address-family ipv4 vrf CUSTOMER
Option B is correct because the BGP configuration shows that the neighbor 10.1.1.1 is configured under the BGP IPv4 unicast address-family, but not under the address-family ipv4 vrf CUSTOMER. For a VRF to install a route learned via eBGP from a CE router, the neighbor must be explicitly activated under the VRF address-family. Without this, the PE will receive the default route but will not place it into the VRF routing table.
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.
✗
The redistribute connected command under the VRF is overwriting the default route
Why it's wrong here
Incorrect. Redistribution does not delete existing routes; it only injects connected routes.
✓
The neighbor 10.1.1.1 is not configured under the address-family ipv4 vrf CUSTOMER
Why this is correct
Correct. Without activating the neighbor under the VRF address-family, eBGP routes from CE are not imported into the VRF.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The next-hop-self under the VRF address-family is not set
Why it's wrong here
Incorrect. Next-hop-self is used for advertisement to other PEs, not for route installation from CE.
✗
The default-information originate command is missing
Why it's wrong here
Incorrect. This command is used in OSPF to generate a default route; not relevant for BGP.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between configuring a BGP neighbor globally versus under a VRF address-family, tricking candidates into thinking that a neighbor statement under router bgp is sufficient for VRF route installation.
Trap categories for this question
Command / output trap
Incorrect. This command is used in OSPF to generate a default route; not relevant for BGP.
Detailed technical explanation
How to think about this question
In MPLS L3VPN, a VRF defines a separate routing table, and BGP sessions for VRF routes must be configured under the 'address-family ipv4 vrf <name>' context. The neighbor activation under this address-family is what tells BGP to store learned routes in the VRF's RIB. Without it, the route is received in the global BGP table but never imported into the VRF, even if the VRF's route-target import policy is configured. This is a common misconfiguration when migrating from global BGP to VRF-aware BGP.
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 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.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Services — This question tests Services — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The neighbor 10.1.1.1 is not configured under the address-family ipv4 vrf CUSTOMER — Option B is correct because the BGP configuration shows that the neighbor 10.1.1.1 is configured under the BGP IPv4 unicast address-family, but not under the address-family ipv4 vrf CUSTOMER. For a VRF to install a route learned via eBGP from a CE router, the neighbor must be explicitly activated under the VRF address-family. Without this, the PE will receive the default route but will not place it into the VRF routing table.
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.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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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