The correct answer is that the router is not used as a transit path but still has routes. When the set-overload-bit command is applied, the IS-IS router sets the overload bit in its Link State Packets (LSPs), signaling to all other routers in the area that it should not be used for transit traffic, even though it continues to advertise its own directly connected prefixes and can still be reached as a destination. This effect is immediate because other routers recalculate their SPF trees upon receiving the updated LSP, excluding the overloaded router from any shortest-path calculations for through traffic. On the Cisco SPCOR 350-501 exam, this concept tests your understanding of IS-IS network stability mechanisms, often appearing in a scenario where a router is being introduced or removed from service. A common trap is assuming the router stops participating in SPF or drops adjacencies, but it remains fully adjacent and still runs SPF for its own routes. Memory tip: think of the overload bit as a “do not disturb” sign for transit traffic, but the router still answers the door for its own destinations.
350-501 Networking Practice Question
This 350-501 practice question tests your understanding of networking. 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.
An engineer configures the 'set-overload-bit' command on an IS-IS router. What is the immediate effect on the network?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The router is not used as a transit path but still has routes.
Option C is correct because setting the overload bit in IS-IS LSPs tells other routers not to use this router for transit traffic, but it still advertises its own prefixes and can be a destination. Option A is incorrect; the router still participates in SPF. Option B is incorrect; LSPs are still advertised. Option D is incorrect; neighbors remain adjacent.
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.
✗
The router stops participating in SPF calculations.
Why it's wrong here
Incorrect. The router still runs SPF.
✗
The router's LSPs are no longer advertised.
Why it's wrong here
Incorrect. LSPs are still advertised with the overload bit set.
✗
The router's neighbors drop adjacency.
Why it's wrong here
Incorrect. Adjacency remains.
✓
The router is not used as a transit path but still has routes.
Why this is correct
Correct. Overload bit prevents transit traffic while still being reachable.
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: The router is not used as a transit path but still has routes. — Option C is correct because setting the overload bit in IS-IS LSPs tells other routers not to use this router for transit traffic, but it still advertises its own prefixes and can be a destination. Option A is incorrect; the router still participates in SPF. Option B is incorrect; LSPs are still advertised. Option D is incorrect; neighbors remain adjacent.
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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