- A
Interface state change
Correct. An interface state change directly adds or removes directly connected routes from the routing table.
- B
System uptime
Why wrong: Incorrect. System uptime is a metric but does not itself trigger routing table changes.
- C
Log file rotation
Why wrong: Incorrect. Log file rotation is a maintenance task unrelated to routing table dynamics.
- D
BGP neighbor reset
Correct. Resetting a BGP neighbor tears down and re-establishes the session, causing withdrawal and re-advertisement of BGP routes.
- E
Configuration commit
Why wrong: Incorrect. A configuration commit activates configuration but does not directly modify the routing table unless the configuration itself triggers a protocol or interface change.
Question 507 of 514
What Triggers a Routing Table Change in Junos?
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. A key principle to apply: routing table. 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.)
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.
Answer choices
Why each option matters
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. When an interface goes up, Junos adds the corresponding directly connected route to the routing table; when it goes down, the route is removed. Similarly, a BGP neighbor reset causes the BGP session to be torn down and re-established, which triggers the withdrawal and re-advertisement of all BGP routes, thereby modifying the routing table.
Key principle: Routing table
Answer analysis
Option-by-option breakdown
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
Correct. An interface state change directly adds or removes directly connected routes from the routing table.
Related concept
Routing table
- ✗
System uptime
Why it's wrong here
Incorrect. System uptime is a metric but does not itself trigger routing table changes.
- ✗
Log file rotation
Why it's wrong here
Incorrect. Log file rotation is a maintenance task unrelated to routing table dynamics.
- ✓
BGP neighbor reset
Why this is correct
Correct. Resetting a BGP neighbor tears down and re-establishes the session, causing withdrawal and re-advertisement of BGP routes.
Related concept
Routing table
- ✗
Configuration commit
Why it's wrong here
Incorrect. A configuration commit activates configuration but does not directly modify the routing table unless the configuration itself triggers a protocol or interface change.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse a configuration commit (option E) with an automatic routing table change. 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
How to think about this question
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.
KKey Concepts to Remember
- Routing table
- Interface state change
- BGP neighbor reset
- Configuration commit
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Routing table
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 routing table, then practise related JNCIA-JUNOS questions on the same topic to reinforce the concept.
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Operational Monitoring and Maintenance — study guide chapter
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FAQ
Questions learners often ask
What does this JNCIA-JUNOS question test?
Operational Monitoring and Maintenance — This question tests Operational Monitoring and Maintenance — Routing table.
What is the correct answer to this question?
The correct answer is: Interface state change — An interface state change (up/down) directly affects the reachability of directly connected networks. When an interface goes up, Junos adds the corresponding directly connected route to the routing table; when it goes down, the route is removed. Similarly, a BGP neighbor reset causes the BGP session to be torn down and re-established, which triggers the withdrawal and re-advertisement of all BGP routes, thereby modifying the routing table.
What should I do if I get this JNCIA-JUNOS question wrong?
Review routing table, then practise related JNCIA-JUNOS questions on the same topic to reinforce the concept.
What is the key concept behind this question?
Routing table
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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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