Quick Answer
The answer is an interface state change and a BGP neighbor reset. An interface transitioning up or down alters the reachability of directly connected networks, prompting Junos to add or remove those routes from the routing table. Similarly, resetting a BGP neighbor tears down and re-establishes the TCP session, which forces the withdrawal and re-advertisement of all BGP routes, directly modifying the table. On the JNCIA-Junos exam, this question tests your understanding of route sources and the events that cause Junos to recalculate forwarding paths—a common trap is forgetting that static routes or OSPF neighbor flapping also trigger changes, but the two most direct triggers are physical interface events and BGP session resets. To remember, think “link up/down and peer reset” as the two immediate causes for routing table updates.
This JNCIA-JUNOS practice question tests your understanding of operational monitoring and maintenance. 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 events typically trigger a change to the routing table? (Choose two.)
Interface state change
Directly triggers routing table updates.
System uptime
Why wrong: Not a trigger for routing changes.
Log file rotation
Why wrong: Does not affect routing table.
BGP neighbor reset
Causes routes to be withdrawn or updated.
Configuration commit
Why wrong: May trigger routing changes but not guaranteed immediate.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Interface state change
An interface state change (up/down) directly affects the reachability of directly connected networks, causing Junos to add or remove the corresponding routes from the routing table. Similarly, a BGP neighbor reset tears down and re-establishes the TCP session, which triggers the withdrawal and re-advertisement of all BGP routes, thus modifying the routing table.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Interface state change
Why this is correct
Directly triggers routing table updates.
Related concept
Read the scenario before looking for a memorised answer.
System uptime
Why it's wrong here
Not a trigger for routing changes.
Log file rotation
Why it's wrong here
Does not affect routing table.
BGP neighbor reset
Why this is correct
Causes routes to be withdrawn or updated.
Related concept
Read the scenario before looking for a memorised answer.
Configuration commit
Why it's wrong here
May trigger routing changes but not guaranteed immediate.
Common exam traps
The trap here is that candidates often confuse a configuration commit with an automatic routing table change, but a commit only activates the configuration; it does not directly modify the routing table unless the configuration itself triggers a protocol event or interface change.
Detailed technical explanation
Under the hood, Junos maintains separate routing tables (inet.0, inet6.0, etc.) that are updated by the Routing Engine based on events from the kernel (interface state) or routing protocol state machines (BGP, OSPF, IS-IS). A BGP neighbor reset causes the BGP finite state machine to transition from Established to Idle, clearing all received NLRIs and re-initiating the OPEN/UPDATE exchange, which can lead to transient route flapping. In real-world networks, an interface flap or BGP reset can cause significant routing table churn, impacting convergence time and potentially causing traffic loss.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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
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FAQ
Operational Monitoring and Maintenance — This question tests Operational Monitoring and Maintenance — Read the scenario before looking for a memorised answer..
The correct answer is: Interface state change — An interface state change (up/down) directly affects the reachability of directly connected networks, causing Junos to add or remove the corresponding routes from the routing table. Similarly, a BGP neighbor reset tears down and re-establishes the TCP session, which triggers the withdrawal and re-advertisement of all BGP routes, thus modifying the routing table.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
This JNCIA-JUNOS practice question is part of Courseiva's free Juniper Networks certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the JNCIA-JUNOS exam.
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