Quick Answer
The answer is preference and metric, as Junos uses these two attributes in sequence to select the active route among multiple routes to the same destination. Preference, also known as administrative distance, is evaluated first as a locally configurable value that ranks the trustworthiness of the routing protocol source—lower preference wins. If multiple routes share the same preference, Junos then compares the metric, a protocol-specific value such as OSPF cost or RIP hop count, to break the tie. On the JNCIA-Junos exam, this concept tests your understanding of the Junos route selection process, often appearing in questions that ask which attributes are compared before and after the routing table is built. A common trap is confusing preference with metric: remember that preference is a local, protocol-independent ranking, while metric is only compared within the same protocol. A helpful memory tip is "Preference first, metric second"—think of preference as the gatekeeper that decides which protocol’s routes are even considered, and metric as the tiebreaker within that protocol.
This JNCIA-JUNOS practice question tests your understanding of routing fundamentals. 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 attributes are used by Junos to select the active route among multiple routes to the same destination?
Metric
Lower metric is preferred when preference is equal.
Preference
Lower preference is preferred.
Protocol type
Why wrong: Protocol type is factored into preference.
Next hop address
Why wrong: Next hop is not used for selection.
AS path length
Why wrong: AS path is used in BGP but not in general route selection.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Metric
Junos uses the route preference (also known as administrative distance) as the primary attribute to select the active route among multiple routes to the same destination. If multiple routes have the same preference, Junos then compares the metric (also called cost or protocol-specific metric) to break the tie. Preference is a local, configurable value that ranks the trustworthiness of the routing protocol source, while metric is a protocol-specific value (e.g., OSPF cost, RIP hop count) used within the same protocol.
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.
Metric
Why this is correct
Lower metric is preferred when preference is equal.
Related concept
Read the scenario before looking for a memorised answer.
Preference
Why this is correct
Lower preference is preferred.
Related concept
Read the scenario before looking for a memorised answer.
Protocol type
Why it's wrong here
Protocol type is factored into preference.
Next hop address
Why it's wrong here
Next hop is not used for selection.
AS path length
Why it's wrong here
AS path is used in BGP but not in general route selection.
Common exam traps
The trap here is that candidates often confuse Junos's use of 'preference' with Cisco's 'administrative distance' and mistakenly think 'protocol type' or 'next hop address' are selection attributes, when in fact Junos uses preference and metric as the two standard tiebreakers for active route selection.
Detailed technical explanation
In Junos, the route preference is a numerical value from 0 to 4,294,967,295 (defaults vary by protocol, e.g., direct=0, static=5, OSPF=10, IS-IS=15, RIP=100, BGP=170). When two routes from different protocols have the same preference, Junos uses the metric, which is protocol-specific (e.g., OSPF cost, RIP hop count, BGP MED). If both preference and metric are identical, Junos may use additional tiebreakers like the route's next-hop interface or the route's source address, but preference and metric are the primary two attributes explicitly tested in JNCIA.
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
Routing Fundamentals — This question tests Routing Fundamentals — Read the scenario before looking for a memorised answer..
The correct answer is: Metric — Junos uses the route preference (also known as administrative distance) as the primary attribute to select the active route among multiple routes to the same destination. If multiple routes have the same preference, Junos then compares the metric (also called cost or protocol-specific metric) to break the tie. Preference is a local, configurable value that ranks the trustworthiness of the routing protocol source, while metric is a protocol-specific value (e.g., OSPF cost, RIP hop count) used within the same protocol.
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 11, 2026
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