Quick Answer
The correct answer is that Segment Routing’s primary advantage over RSVP-TE is the elimination of per-flow state on transit routers. This is because Segment Routing encodes the entire forwarding path directly into the packet header as a list of segment identifiers, so intermediate routers simply forward based on these instructions without needing to maintain a separate label-switched path (LSP) state for each traffic flow. In contrast, RSVP-TE requires every transit router to store per-flow reservation and path information, consuming memory and processing overhead. On the Cisco SPCOR 350-501 exam, this concept tests your understanding of MPLS control-plane scalability; a common trap is confusing fast-reroute or ECMP support, which both technologies offer, or assuming a central controller is mandatory for SR. Remember the memory tip: “SR steers with stickers, not state”—the path is in the packet, not the router.
This 350-501 practice question tests your understanding of architecture. 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.
A service provider wants to implement Segment Routing in its MPLS core to simplify traffic engineering. What is the primary advantage of Segment Routing over traditional RSVP-TE?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "primary"
Why it matters: Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.
No per-flow state on transit routers
SR uses source routing; transit routers only need label forwarding.
Improved ECMP load balancing
Why wrong: Both can use ECMP.
Better support for Fast Reroute
Why wrong: Both SR and RSVP-TE support FRR.
Requires a central controller for path calculation
Why wrong: SR can be deployed without a controller.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
No per-flow state on transit routers
Option C is correct because Segment Routing eliminates per-flow state on intermediate routers by encoding the path in the packet header. Option A is wrong because both can support fast-reroute. Option B is wrong because ECMP is supported by both. Option D is wrong because SR doesn't necessarily require a central controller.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
No per-flow state on transit routers
Why this is correct
SR uses source routing; transit routers only need label forwarding.
Clue confirmation
The clue word "primary" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.
Improved ECMP load balancing
Why it's wrong here
Both can use ECMP.
Better support for Fast Reroute
Why it's wrong here
Both SR and RSVP-TE support FRR.
Requires a central controller for path calculation
Why it's wrong here
SR can be deployed without a controller.
Common exam traps
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
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
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related 350-501 NAT questions on configuration and troubleshooting.
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Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
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FAQ
Architecture — This question tests Architecture — Static NAT maps one inside address to one outside address..
The correct answer is: No per-flow state on transit routers — Option C is correct because Segment Routing eliminates per-flow state on intermediate routers by encoding the path in the packet header. Option A is wrong because both can support fast-reroute. Option B is wrong because ECMP is supported by both. Option D is wrong because SR doesn't necessarily require a central controller.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related 350-501 NAT questions on configuration and troubleshooting.
Yes — watch for: "primary". Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.
Static NAT maps one inside address to one outside address.
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Last reviewed: Jun 24, 2026
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