The answer is enabling MPLS on all interfaces that participate in segment routing forwarding and configuring the IGP (OSPF or IS-IS) for segment routing. These two tasks are required because segment routing relies on the IGP to advertise prefix-SIDs and adjacency-SIDs, which are the labels that steer traffic through the network, while MPLS must be enabled on interfaces to actually forward packets based on those labels. On the Cisco SPCOR 350-501 exam, this question tests your understanding of how segment routing replaces traditional MPLS signaling protocols—a common trap is assuming LDP or RSVP-TE is still needed, but segment routing eliminates them by encoding label information directly into the IGP. Remember the memory tip: “IGP for the SIDs, MPLS for the forwarding”—if you see LDP or RSVP-TE in the options, they are distractors, not required tasks.
350-501 Networking Practice Question
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 TWO tasks are required when implementing segment routing in an MPLS network?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Configure the IGP (OSPF or IS-IS) with segment routing extensions
Options A and B are correct. Configuring the IGP (OSPF or IS-IS) for segment routing is essential to advertise prefix-SIDs and adjacency-SIDs. Enabling MPLS on interfaces ensures MPLS forwarding. Option C is not required because LDP is replaced by segment routing. Option D is not required as RSVP-TE is a different traffic engineering mechanism. Option E is part of the MPLS forwarding plane setup but not unique to segment routing; it is a prerequisite.
Key principle: OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Configure RSVP-TE to establish LSPs
Why it's wrong here
RSVP-TE is a separate traffic engineering protocol, not required for segment routing.
✗
Enable CEF on all routers
Why it's wrong here
CEF is required for MPLS but is a generic prerequisite, not a task specific to segment routing implementation.
✓
Configure the IGP (OSPF or IS-IS) with segment routing extensions
Why this is correct
IGP must be configured to support segment routing and advertise labels (prefix-SIDs).
LDP is not needed because segment routing uses IGP to distribute labels.
Common exam traps
Common exam trap: OSPF can fail even when IP connectivity looks correct
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
How to think about this question
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.
KKey Concepts to Remember
OSPF neighbours must agree on key parameters.
Router ID selection can affect neighbour relationships and LSDB output.
OSPF cost influences the preferred path.
A route can appear in OSPF information but not become the installed route.
TExam Day Tips
→Check area mismatch first when OSPF adjacency fails.
→Review passive interfaces when a network is advertised but no neighbour forms.
→Use show ip ospf neighbor and show ip route clues carefully.
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
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.
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.
Networking — This question tests Networking — OSPF neighbours must agree on key parameters..
What is the correct answer to this question?
The correct answer is: Configure the IGP (OSPF or IS-IS) with segment routing extensions — Options A and B are correct. Configuring the IGP (OSPF or IS-IS) for segment routing is essential to advertise prefix-SIDs and adjacency-SIDs. Enabling MPLS on interfaces ensures MPLS forwarding. Option C is not required because LDP is replaced by segment routing. Option D is not required as RSVP-TE is a different traffic engineering mechanism. Option E is part of the MPLS forwarding plane setup but not unique to segment routing; it is a prerequisite.
What should I do if I get this 350-501 question wrong?
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.
What is the key concept behind this question?
OSPF neighbours must agree on key parameters.
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