This 200-301 practice question tests your understanding of ip routing. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. A key principle to apply: a router uses the longest-prefix match rule to select the most specific route that matches the destination IP address for packet forwarding.. 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.
What is the main reason a more specific route usually overrides a less specific route, even when both point to valid destinations?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Because routing prefers the most specific matching prefix.
A more specific route overrides a less specific route because longest-prefix match is the core logic used for route selection among matching destinations. In plain language, the router prefers the entry that most narrowly and accurately describes the actual destination network. This makes routing behavior precise and predictable, especially when summary routes and more detailed routes coexist.
If routers did not prefer the more specific match, detailed route information would not provide much value. The correct answer is the one that explains route choice in terms of specificity rather than protocol type alone.
Key principle: A router uses the longest-prefix match rule to select the most specific route that matches the destination IP address for packet forwarding.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Because routing prefers the most specific matching prefix.
Why this is correct
This is correct because longest-prefix match is the rule that gives more specific routes priority.
Related concept
A router uses the longest-prefix match rule to select the most specific route that matches the destination IP address for packet forwarding.
✗
Because less specific routes are always invalid.
Why it's wrong here
This is wrong because summary and default routes are valid and useful; they are just less specific.
When this WOULD be correct
In a different question, if it asked about the validity of routes in a scenario where only specific prefixes are allowed, stating that less specific routes are invalid could be correct. For example, if the question specified a routing protocol that only accepts exact matches, then this option could apply.
✗
Because more specific routes always have a lower administrative distance.
In a different question setup where the focus is on comparing routes based on their administrative distances rather than specificity, this option could be correct. For example, if the question asked why a route with a lower administrative distance is preferred over one with a higher distance, option C would be valid.
✗
Because OSPF requires every route to be /32.
Why it's wrong here
This is wrong because OSPF supports many prefix lengths and does not require /32 routes.
When this WOULD be correct
In a question asking about OSPF configurations where only host routes are being considered, and the context specifies that OSPF must use /32 for those routes, this option would be correct. For example, if the question states that OSPF is being used exclusively for point-to-point links, then /32 routes would be required.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.
✓Because routing prefers the most specific matching prefix.Correct answer▾
Why this is correct
This is correct because longest-prefix match is the rule that gives more specific routes priority.
✗Because less specific routes are always invalid.Wrong answer — click to see why▾
Why this is wrong here
This option is incorrect because less specific routes can still be valid; they simply provide broader coverage and may not necessarily be invalid. Routing protocols can have valid less specific routes that coexist with more specific ones.
★ When this WOULD be the correct answer
In a different question, if it asked about the validity of routes in a scenario where only specific prefixes are allowed, stating that less specific routes are invalid could be correct. For example, if the question specified a routing protocol that only accepts exact matches, then this option could apply.
Why candidates choose this
Candidates might choose this option due to a misunderstanding of routing concepts, conflating the validity of routes with their specificity, leading them to believe that less specific routes cannot exist in a valid routing table.
✗Because more specific routes always have a lower administrative distance.Wrong answer — click to see why▾
Why this is wrong here
This option is wrong because administrative distance is a separate metric used to determine the trustworthiness of a route, not its specificity. More specific routes can have varying administrative distances, and this does not inherently dictate which route will be preferred.
★ When this WOULD be the correct answer
In a different question setup where the focus is on comparing routes based on their administrative distances rather than specificity, this option could be correct. For example, if the question asked why a route with a lower administrative distance is preferred over one with a higher distance, option C would be valid.
Why candidates choose this
Candidates may choose this option due to a misunderstanding of routing protocols, conflating the concepts of route specificity and administrative distance, leading them to believe that lower administrative distance always correlates with more specific routes.
✗Because OSPF requires every route to be /32.Wrong answer — click to see why▾
Why this is wrong here
This option is incorrect because OSPF does not require every route to be /32; it can support various subnet masks. The requirement for /32 routes is specific to certain scenarios, such as host routes, but does not apply universally to all OSPF routes.
★ When this WOULD be the correct answer
In a question asking about OSPF configurations where only host routes are being considered, and the context specifies that OSPF must use /32 for those routes, this option would be correct. For example, if the question states that OSPF is being used exclusively for point-to-point links, then /32 routes would be required.
Why candidates choose this
Candidates may choose this option due to a misunderstanding of OSPF's behavior with host routes, mistakenly believing that all OSPF routes must be /32, leading to confusion about the specifics of routing protocols.
Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Common exam traps
Common exam trap: answer the scenario, not the keyword
A frequent exam trap is assuming that the route with the lowest administrative distance or a specific routing protocol preference always overrides others, regardless of prefix length. Candidates might incorrectly think that OSPF requires /32 routes or that less specific routes are invalid. This misunderstanding leads to choosing answers based on protocol rules or administrative distance alone, ignoring the fundamental longest-prefix match principle. Remember, the router always prefers the most specific route that matches the destination IP, even if the less specific route has a better administrative distance or comes from a preferred protocol.
Detailed technical explanation
How to think about this question
Routing in IP networks relies on the principle of longest-prefix match, which means that when a router receives a packet, it searches its routing table for the route entry with the most specific subnet mask that matches the destination IP address. This specificity is determined by the prefix length: the longer the prefix, the more specific the route. For example, a /28 route is more specific than a /24 route. This ensures that traffic is forwarded along the most precise path available, optimizing network efficiency and accuracy.
The decision process in routing involves comparing all matching routes for a destination and selecting the one with the longest prefix. This rule overrides other factors like administrative distance or metric when multiple routes point to the same destination but differ in specificity. Cisco routers implement this longest-prefix match rule consistently, which means that even if a less specific route has a better administrative distance, the more specific route will be preferred if both are valid.
A common exam trap is confusing route specificity with administrative distance or protocol requirements. For example, some may incorrectly believe that OSPF requires /32 routes or that more specific routes always have lower administrative distances. In reality, OSPF supports various prefix lengths, and administrative distance is a separate metric used only when prefix lengths are equal. Understanding this distinction helps avoid mistakes and clarifies why routing tables prioritize longest-prefix matches for precise packet forwarding.
KKey Concepts to Remember
A router uses the longest-prefix match rule to select the most specific route that matches the destination IP address for packet forwarding.
Routing decisions prioritize prefix length specificity over administrative distance when multiple valid routes to the same destination exist.
Administrative distance is used only when routes have equal prefix lengths to determine the preferred routing protocol.
Routing protocols like OSPF and EIGRP support a variety of prefix lengths and do not require fixed subnet masks such as /32.
Less specific routes, such as default or summary routes, remain valid and are used only when no more specific route matches the destination.
The longest-prefix match ensures precise and predictable routing behavior, especially when detailed and summary routes coexist in the routing table.
Routers compare all matching routes and install the route with the longest prefix in the forwarding table for efficient packet delivery.
Confusing route specificity with administrative distance or protocol requirements can lead to incorrect routing decisions and exam mistakes.
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
A router uses the longest-prefix match rule to select the most specific route that matches the destination IP address for packet forwarding.
Real-world example
How this comes up in practice
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 200-301 question in full detail.
Review a router uses the longest-prefix match rule to select the most specific route that matches the destination IP address for packet forwarding., then practise related 200-301 questions on the same topic to reinforce the concept.
IP Routing — This question tests IP Routing — A router uses the longest-prefix match rule to select the most specific route that matches the destination IP address for packet forwarding..
What is the correct answer to this question?
The correct answer is: Because routing prefers the most specific matching prefix. — A more specific route overrides a less specific route because longest-prefix match is the core logic used for route selection among matching destinations. In plain language, the router prefers the entry that most narrowly and accurately describes the actual destination network. This makes routing behavior precise and predictable, especially when summary routes and more detailed routes coexist.
If routers did not prefer the more specific match, detailed route information would not provide much value. The correct answer is the one that explains route choice in terms of specificity rather than protocol type alone.
What should I do if I get this 200-301 question wrong?
Review a router uses the longest-prefix match rule to select the most specific route that matches the destination IP address for packet forwarding., then practise related 200-301 questions on the same topic to reinforce the concept.
What is the key concept behind this question?
A router uses the longest-prefix match rule to select the most specific route that matches the destination IP address for packet forwarding.
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