- A
Compare the MED.
Why wrong: MED is compared after AS path length.
- B
Compare the AS path length.
After local preference, BGP selects the path with the shortest AS path.
- C
Compare the IGP metric to the next-hop.
Why wrong: IGP metric is compared after MED and before BGP ID.
- D
Compare the origin code.
Why wrong: Origin code is compared after AS path length and MED.
Question 149 of 514
What Is the Next Step in BGP Path Selection After Local Preference?
This JNCIA-JUNOS practice question tests your understanding of routing fundamentals. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 network engineer is troubleshooting a BGP routing issue. The router receives a route to 172.16.0.0/16 from two BGP peers with different local preferences. The route from peer A has local preference 200, and from peer B has local preference 100. The router selects the route from peer A. What is the next step in BGP path selection if the local preferences were equal?
Quick Answer
The answer is to compare the AS path length. After BGP path selection evaluates local preference, the next tie-breaking step is to prefer the route with the shortest AS path length, as this typically indicates a more direct path to the destination network. On the Juniper Networks Certified Associate Junos JNCIA-Junos exam, this sequence is a frequent topic, testing your understanding of the BGP path selection algorithm order. A common trap is confusing the order of local preference and AS path length, or jumping ahead to metrics like MED or IGP cost. To remember the correct sequence, use the mnemonic "We Love Oranges AS Oranges Mean Pure Refreshment," where the "AS" stands for AS path length, coming right after local preference.
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
✓
Compare the AS path length.
B is correct because in BGP path selection, after comparing local preference (highest wins), the next tiebreaker is the shortest AS path length. If local preferences are equal, the router compares the AS path length, selecting the route with fewer AS numbers. This is defined in RFC 4271 and is the second step in the BGP decision process.
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.
- ✗
Compare the MED.
Why it's wrong here
MED is compared after AS path length.
- ✓
Compare the AS path length.
Why this is correct
After local preference, BGP selects the path with the shortest AS path.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Compare the IGP metric to the next-hop.
- ✗
Compare the origin code.
Why it's wrong here
Origin code is compared after AS path length and MED.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse the order of BGP path selection steps, mistakenly thinking MED is compared immediately after local preference, when in fact AS path length and origin code come before MED in the Junos BGP decision process.
Detailed technical explanation
How to think about this question
The BGP path selection algorithm has 13 steps in Junos, with local preference (step 2) and AS path length (step 3) being early tiebreakers. The AS path length counts the number of AS_SEQUENCE segments, but AS_SET segments are counted as 1 regardless of the number of ASes within them, which can lead to subtle routing decisions. In real-world scenarios, manipulating AS path prepending is a common technique to influence inbound traffic, but it only takes effect after local preference is equal.
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.
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
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 exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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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: Compare the AS path length. — B is correct because in BGP path selection, after comparing local preference (highest wins), the next tiebreaker is the shortest AS path length. If local preferences are equal, the router compares the AS path length, selecting the route with fewer AS numbers. This is defined in RFC 4271 and is the second step in the BGP decision process.
What should I do if I get this JNCIA-JUNOS question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jul 4, 2026
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