Quick Answer
The more specific prefix is the correct choice because a router always prefers the longest prefix match when making a forwarding decision, regardless of administrative distance or metric. This fundamental rule of IP routing dictates that the route with the highest subnet mask length represents the most precise path to the destination, so it is selected first from the routing table. On the Cisco SPCOR / CCNP Service Provider Core 350-501 exam, this concept is frequently tested in the context of service provider routing architectures, where overlapping prefixes from BGP or IGP may exist. A common trap is assuming a lower administrative distance or better metric overrides prefix length—it does not; the longest match always wins first. For a quick memory tip, remember: “Longer is stronger”—the more specific the mask, the stronger the route preference.
This 350-501 practice question tests your understanding of networking. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 router receives a route with a higher specific prefix length than the same prefix in the routing table. Which route will be preferred?
The route with higher administrative distance.
Why wrong: AD is used when multiple protocols provide the same prefix length.
The route with lower metric.
Why wrong: Metric is compared after longest match and AD.
The more specific prefix.
Longest prefix match is the primary criterion in IP routing.
The less specific prefix.
Why wrong: Less specific prefixes are only used if no more specific match exists.
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 more specific prefix.
C is correct because a router always prefers the most specific prefix (longest prefix length) when forwarding packets, regardless of administrative distance or metric. This is a fundamental rule of IP routing: the route with the longest subnet mask match is chosen first, as it represents the most precise path to the destination.
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 route with higher administrative distance.
Why it's wrong here
AD is used when multiple protocols provide the same prefix length.
The route with lower metric.
The more specific prefix.
Why this is correct
Longest prefix match is the primary criterion in IP routing.
Related concept
Read the scenario before looking for a memorised answer.
The less specific prefix.
Why it's wrong here
Less specific prefixes are only used if no more specific match exists.
Common exam traps
Cisco often tests the misconception that administrative distance or metric can override the longest prefix match, leading candidates to incorrectly choose option A or B when the question explicitly states a higher specific prefix length.
Detailed technical explanation
The longest prefix match (LPM) algorithm is implemented in the forwarding information base (FIB) and is evaluated before any routing protocol decision. For example, a /32 host route will always be chosen over a /24 summary route for the same destination IP, even if the /24 route has a lower administrative distance (e.g., 1 vs. 120). This behavior is defined in RFC 1812 and is consistent across all dynamic routing protocols (OSPF, EIGRP, BGP) and static routes.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
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FAQ
Networking — This question tests Networking — Read the scenario before looking for a memorised answer..
The correct answer is: The more specific prefix. — C is correct because a router always prefers the most specific prefix (longest prefix length) when forwarding packets, regardless of administrative distance or metric. This is a fundamental rule of IP routing: the route with the longest subnet mask match is chosen first, as it represents the most precise path to the destination.
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 25, 2026
This 350-501 practice question is part of Courseiva's free Cisco 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 350-501 exam.
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