The correct action is to execute 'clear ip ospf process' on all routers along the expected path. This resolves the OSPF LSA flooding issue in Segment Routing because a delayed or blocked LSA flood prevents the Link-State Database from reflecting the newly restored link, causing routers to retain stale topology information and compute suboptimal SPF paths even after IGP convergence is reported complete. On the Cisco SPCOR 350-501 exam, this scenario tests your understanding that Segment Routing convergence depends on timely OSPF LSA propagation, not just label allocation or SR-TE policies; a common trap is assuming the problem lies with adjacency SIDs or misconfigured policies when the root cause is a flooded LSA not reaching all routers. Remember that in a single-area OSPF network with 100 routers, a missing Type 1 or Type 2 LSA can silently break shortest-path calculations for SR-capable nodes. Memory tip: “Flood first, then SPF — if the path is wrong, clear the flood along.”
350-501 MPLS and Segment Routing Practice Question
This 350-501 practice question tests your understanding of mpls and segment routing. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 has deployed segment routing with OSPF as the IGP in its core network. The network consists of 100 routers in a single area. The operations team reports that after a link failure between Router X and Router Y, traffic from Router A to Router B is taking a suboptimal path even though IGP convergence is complete and all routers have updated their LSDB. Router A and Router B are both segment routing capable. The team verifies that no SR-TE policies are configured and that all routers are using the default SPF algorithm. The expected shortest path from A to B should go through the newly restored link, but instead it still traverses an alternate path. Which action should resolve the issue?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Execute 'clear ip ospf process' on all routers along the expected path.
Option D is correct: The issue is likely that OSPF link-state advertisement (LSA) flooding is delayed or blocked, preventing the repair of the LSDB. 'clear ip ospf process' forces a fresh LSA flood and SPF computation. Option A is wrong because SR-TE policies are not used. Option B is wrong because the problem is not with label allocation but with routing. Option C is wrong because adjacency SIDs are automatically allocated and not the root cause.
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.
✗
Remove and re-add the adjacency SID configuration on the restored link.
Why it's wrong here
Adjacency SIDs are dynamically allocated; this would not force SPF re-computation.
✓
Execute 'clear ip ospf process' on all routers along the expected path.
Why this is correct
This forces OSPF to re-flood LSAs and run SPF, ensuring the restored link is considered in the shortest path tree.
Configure an SR-TE policy from A to B with an explicit path using the restored link.
Why it's wrong here
This would fix the path but is a workaround; the root cause is IGP convergence. Also, SR-TE policies are not in use.
✗
Issue 'clear mpls forwarding labels' on Router A to rebuild the label table.
Why it's wrong here
The label table is correct; the issue is the routing decision based on the LSDB.
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.
MPLS and Segment Routing — This question tests MPLS and Segment Routing — OSPF neighbours must agree on key parameters..
What is the correct answer to this question?
The correct answer is: Execute 'clear ip ospf process' on all routers along the expected path. — Option D is correct: The issue is likely that OSPF link-state advertisement (LSA) flooding is delayed or blocked, preventing the repair of the LSDB. 'clear ip ospf process' forces a fresh LSA flood and SPF computation. Option A is wrong because SR-TE policies are not used. Option B is wrong because the problem is not with label allocation but with routing. Option C is wrong because adjacency SIDs are automatically allocated and not the root cause.
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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