The answer is explicit path selection and bandwidth reservation. These two characteristics differentiate MPLS Traffic Engineering from pure MPLS forwarding because MPLS-TE allows you to define a specific, explicit path for a label-switched path (LSP) rather than relying solely on the shortest-path IGP metric, and it can reserve a guaranteed amount of bandwidth along that path to prevent congestion. In contrast, pure MPLS forwarding simply swaps labels hop-by-hop without any awareness of path constraints or available bandwidth. On the Cisco SPCOR 350-501 exam, this concept tests your understanding of how MPLS-TE provides traffic control beyond basic label switching; a common trap is confusing MPLS-TE’s explicit path with the implicit path of LDP. Remember the mnemonic “EB” for Explicit path and Bandwidth reservation—if you see either, think MPLS-TE.
350-501 Services Practice Question
This 350-501 practice question tests your understanding of services. 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 of the following are characteristics of MPLS Traffic Engineering that differentiate it from pure MPLS forwarding?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Allows bandwidth reservation
MPLS Traffic Engineering (MPLS-TE) explicitly supports bandwidth reservation, which allows an operator to guarantee a certain amount of bandwidth for a traffic-engineered LSP. This is a key differentiator from pure MPLS forwarding, where LSPs are created without any bandwidth awareness and simply forward packets based on the label-swapping mechanism.
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.
✗
Requires LDP for LSP creation
Why it's wrong here
Incorrect. MPLS TE uses RSVP to create its own LSPs, not LDP.
✓
Allows bandwidth reservation
Why this is correct
Correct. MPLS TE can reserve bandwidth along a path to guarantee QoS.
Related concept
Read the scenario before looking for a memorised answer.
✓
Supports explicit path selection
Why this is correct
Correct. MPLS TE allows administrators to specify the exact path a tunnel takes.
Related concept
Read the scenario before looking for a memorised answer.
✗
Provides optimal load balancing based on topology
Why it's wrong here
Incorrect. MPLS TE does not automatically provide optimal load balancing; it requires explicit configuration.
✗
Uses RSVP for label distribution
Why it's wrong here
Incorrect. While RSVP is used for TE, LDP also distributes labels; the question focuses on characteristics not shared by pure MPLS.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that MPLS-TE requires LDP for LSP creation, but in reality, MPLS-TE uses RSVP-TE for signaling and does not depend on LDP for the TE LSPs themselves.
Detailed technical explanation
How to think about this question
MPLS-TE uses RSVP-TE (RFC 3209) to signal LSPs with explicit path objects (ERO) and bandwidth reservations, enabling constraint-based routing. Under the hood, the TE database is populated by an IGP (OSPF-TE or ISIS-TE) with link attributes like bandwidth and administrative groups, and the path calculation uses CSPF (Constrained Shortest Path First) to find a path that meets the constraints. In a real-world scenario, an operator might reserve 100 Mbps on a TE tunnel to carry VoIP traffic, ensuring that even during congestion, the voice traffic gets its guaranteed bandwidth.
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.
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: Allows bandwidth reservation — MPLS Traffic Engineering (MPLS-TE) explicitly supports bandwidth reservation, which allows an operator to guarantee a certain amount of bandwidth for a traffic-engineered LSP. This is a key differentiator from pure MPLS forwarding, where LSPs are created without any bandwidth awareness and simply forward packets based on the label-swapping mechanism.
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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