Quick Answer
The answer is a missing BGP group configuration, as the Idle state in BGP indicates that the session has not even begun the connection process, and without a defined group, the router has no peers to initiate sessions with. After a Junos upgrade, configuration elements can sometimes be lost or fail to apply, leaving the BGP group undefined and causing all sessions to remain stuck in Idle rather than progressing through Connect or Active states. On the JNCIA-Junos exam, this scenario tests your understanding that Idle is not a transient error but a sign of incomplete configuration—a common trap is to blame routing policies or network reachability when the real issue is a missing group statement. Remember the memory tip: “No group, no peer, Idle is clear.”
This JNCIA-JUNOS practice question tests your understanding of operational monitoring and maintenance. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. 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.
After a software upgrade, BGP sessions are not establishing. The engineer runs 'show bgp summary' and sees that all sessions are in Idle state. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
The BGP group configuration is missing
Without proper configuration, BGP cannot start.
The interface is administratively down
Why wrong: Interface down would show in 'show interfaces', not BGP Idle alone.
The router has a full BGP table
Why wrong: Full table would not prevent session establishment.
The firewall filter is blocking ICMP
Why wrong: BGP uses TCP port 179, not ICMP.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
The BGP group configuration is missing
The Idle state in BGP indicates that the session has not started the connection process, often because the BGP configuration is incomplete or missing. If the BGP group configuration is missing, the router has no peers to initiate sessions with, so all sessions remain in Idle. This is the most likely cause when all sessions are in Idle after a software upgrade, as configuration elements may be lost or not applied.
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.
The BGP group configuration is missing
Why this is correct
Without proper configuration, BGP cannot start.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
The interface is administratively down
Why it's wrong here
Interface down would show in 'show interfaces', not BGP Idle alone.
The router has a full BGP table
Why it's wrong here
Full table would not prevent session establishment.
The firewall filter is blocking ICMP
Common exam traps
The trap here is that candidates often associate Idle state with connectivity issues like interface down or firewall filters, but Idle specifically indicates the BGP process has not been initiated due to missing or incomplete configuration, not a network problem.
Trap categories for this question
Command / output trap
Interface down would show in 'show interfaces', not BGP Idle alone.
Detailed technical explanation
BGP session states follow a finite state machine: Idle, Connect, Active, OpenSent, OpenConfirm, and Established. The Idle state is the initial state, and the router stays there until a start event (e.g., configuration activation) triggers a TCP connection attempt. If the BGP group configuration is missing, no start event occurs, so sessions remain in Idle indefinitely. In real-world scenarios, after a software upgrade, configuration files may not load correctly, leading to missing BGP groups or peers, which is a common troubleshooting point.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A practitioner preparing for the JNCIA-JUNOS exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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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: The BGP group configuration is missing — The Idle state in BGP indicates that the session has not started the connection process, often because the BGP configuration is incomplete or missing. If the BGP group configuration is missing, the router has no peers to initiate sessions with, so all sessions remain in Idle. This is the most likely cause when all sessions are in Idle after a software upgrade, as configuration elements may be lost or not applied.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 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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