- A
Label distribution via LDP or TDP must be consistent across all P routers.
Inconsistent label distribution can cause label mismatch and forwarding failures.
- B
Route reflectors should be used to reduce the number of BGP sessions in the service provider core.
Route reflectors reduce BGP session mesh and improve scalability.
- C
All PE routers must be directly connected via eBGP to exchange VPNv4 routes.
Why wrong: Route reflectors allow iBGP sessions, not direct eBGP between all PEs.
- D
The number of VRFs per PE router is limited by available memory and route processing capacity.
Memory and CPU constraints limit the number of VRFs a PE can support.
- E
The use of BGP next-hop-self is mandatory to prevent routing blackholes in multi-area IGP environments.
Why wrong: Next-hop-self is a design choice, not mandatory; blackholes can be avoided with proper IGP design.
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.
Which THREE factors must be considered when deploying MPLS Layer 3 VPN services to ensure optimal scalability and convergence?
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
Label distribution via LDP or TDP must be consistent across all P routers.
Option A is correct because consistent label distribution across all P (Provider) routers is essential for MPLS L3VPN scalability and convergence. LDP (Label Distribution Protocol) or TDP (Tag Distribution Protocol, Cisco proprietary predecessor) must be uniformly configured to ensure a seamless label-switched path (LSP) from ingress to egress PE. Inconsistent label distribution can cause label binding mismatches, leading to forwarding failures or suboptimal convergence during topology changes.
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.
- ✓
Label distribution via LDP or TDP must be consistent across all P routers.
Why this is correct
Inconsistent label distribution can cause label mismatch and forwarding failures.
Related concept
Read the scenario before looking for a memorised answer.
- ✓
Route reflectors should be used to reduce the number of BGP sessions in the service provider core.
Why this is correct
Route reflectors reduce BGP session mesh and improve scalability.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
All PE routers must be directly connected via eBGP to exchange VPNv4 routes.
Why it's wrong here
Route reflectors allow iBGP sessions, not direct eBGP between all PEs.
- ✓
The number of VRFs per PE router is limited by available memory and route processing capacity.
Why this is correct
Memory and CPU constraints limit the number of VRFs a PE can support.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
The use of BGP next-hop-self is mandatory to prevent routing blackholes in multi-area IGP environments.
Why it's wrong here
Next-hop-self is a design choice, not mandatory; blackholes can be avoided with proper IGP design.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that eBGP is required between PEs for VPNv4 exchange, when in fact iBGP (often with route reflectors) is the standard, and eBGP is only used at the CE-PE edge.
Detailed technical explanation
How to think about this question
In MPLS L3VPN, label distribution via LDP (RFC 5036) ensures that each P router assigns a label for every IGP prefix, enabling hop-by-hop label switching. Route reflectors (RFC 4456) reduce the full-mesh iBGP sessions required for VPNv4 route exchange, scaling the control plane in large service provider cores. VRF scaling on PE routers is constrained by memory (for RIB/FIB) and CPU (for route processing), as each VRF maintains separate routing and forwarding tables, which can become a bottleneck in deployments with thousands of VRFs.
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.
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FAQ
Questions learners often ask
What does this 350-501 question test?
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: Label distribution via LDP or TDP must be consistent across all P routers. — Option A is correct because consistent label distribution across all P (Provider) routers is essential for MPLS L3VPN scalability and convergence. LDP (Label Distribution Protocol) or TDP (Tag Distribution Protocol, Cisco proprietary predecessor) must be uniformly configured to ensure a seamless label-switched path (LSP) from ingress to egress PE. Inconsistent label distribution can cause label binding mismatches, leading to forwarding failures or suboptimal convergence during topology changes.
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.
About these practice questions
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Last reviewed: Jun 25, 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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