- A
The router has 'no-policy-statistics' enabled on the BGP sessions.
Why wrong: This setting does not affect route selection or load balancing.
- B
The BGP routes have different next-hop addresses.
Why wrong: Different next-hops are allowed in BGP multipath; this is not a blocking condition.
- C
The BGP routes are from different autonomous systems.
Junos requires the 'multipath multiple-as' configuration to load balance routes from different ASes; otherwise, only the best path is installed.
- D
The router is configured with 'multipath multiple-as' under BGP.
Why wrong: This is a solution, not a cause. If it were configured, load balancing would work.
Question 260 of 514
Enabling BGP Multipath for Routes from Different ASes in Junos
This JNCIA-JUNOS practice question tests your understanding of routing fundamentals. 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.
A service provider operates a Juniper MX router that receives a default route from two different ISPs via EBGP. Both ISPs advertise 0.0.0.0/0 with the same local preference (100), same AS path length, and same metric. The network administrator wants to load balance outgoing traffic across both ISPs for redundancy and bandwidth utilization. After applying the configuration, the administrator checks the routing table and sees that only one default route is active, the one from ISP-A. The other route from ISP-B is present but not active. The administrator verifies that both routes have the same preference (170) and same BGP attributes. The ISP links are different: ISP-A is connected via interface ge-0/0/0.0 with next-hop 10.1.1.2, and ISP-B via interface ge-0/0/1.0 with next-hop 10.2.2.2. What is the most likely reason that both routes are not active and load-balanced?
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.
Quick Answer
The answer is that the BGP routes are from different autonomous systems. By default, Junos BGP does not install multiple routes from different ASes into the routing table for load balancing, even when all other attributes like local preference, AS path length, and metric are identical. The router selects only the best path, and since both routes are from distinct ISPs with different AS numbers, the second route remains inactive unless the 'multipath multiple-as' command is explicitly configured under the BGP group. This question tests your understanding of BGP multipath behavior on the JNCIA-Junos exam, a common trap where candidates assume equal attributes guarantee load balancing, forgetting the default single-AS restriction. A useful memory tip: think of "multiple AS" as needing the "multiple-as" knob—without it, Junos treats different AS paths as separate best-path candidates, not equal-cost multipath entries.
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
✓
The BGP routes are from different autonomous systems.
The correct answer is C. By default, Junos BGP does not load balance routes from different autonomous systems. To enable multipath across different ASes, the 'multipath multiple-as' command must be configured under BGP. Option A is irrelevant. Option B is not a cause because different next-hops can be load-balanced under multipath. Option D is the solution, not the cause. Therefore, the most likely cause is that the routes are from different ASes.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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 has 'no-policy-statistics' enabled on the BGP sessions.
Why it's wrong here
This setting does not affect route selection or load balancing.
- ✗
The BGP routes have different next-hop addresses.
Why it's wrong here
Different next-hops are allowed in BGP multipath; this is not a blocking condition.
- ✓
The BGP routes are from different autonomous systems.
Why this is correct
Junos requires the 'multipath multiple-as' configuration to load balance routes from different ASes; otherwise, only the best path is installed.
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 router is configured with 'multipath multiple-as' under BGP.
Why it's wrong here
This is a solution, not a cause. If it were configured, load balancing would work.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
- Use explanations to understand the rule behind the answer.
TExam Day Tips
- Underline the problem statement mentally.
- 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
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
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
Got this wrong? Here's your next step.
Identify which JNCIA-JUNOS exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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FAQ
Questions learners often ask
What does this JNCIA-JUNOS question test?
Routing Fundamentals — This question tests Routing Fundamentals — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The BGP routes are from different autonomous systems. — The correct answer is C. By default, Junos BGP does not load balance routes from different autonomous systems. To enable multipath across different ASes, the 'multipath multiple-as' command must be configured under BGP. Option A is irrelevant. Option B is not a cause because different next-hops can be load-balanced under multipath. Option D is the solution, not the cause. Therefore, the most likely cause is that the routes are from different ASes.
What should I do if I get this JNCIA-JUNOS question wrong?
Identify which JNCIA-JUNOS exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
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