CCNA Longest prefix match in routing Practice Question
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: longest prefix match in routing. 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.
Exhibit
R1# show ip route
O 10.60.4.0/24 [110/20] via 192.0.2.2
S 10.60.4.16/28 [1/0] via 192.0.2.6
D 10.60.0.0/16 [90/30720] via 192.0.2.10
Destination being tested: 10.60.4.17
A router has the following routes in its routing table: a static route to 10.60.4.16/28, an OSPF route to 10.60.4.0/24, and an EIGRP route to 10.60.0.0/16. Which route will be used for a packet destined to 10.60.4.17?
R1# show ip route
O 10.60.4.0/24 [110/20] via 192.0.2.2
S 10.60.4.16/28 [1/0] via 192.0.2.6
D 10.60.0.0/16 [90/30720] via 192.0.2.10
Destination being tested: 10.60.4.17
A
The static route to 10.60.4.16/28
This is correct because the destination falls inside the more specific /28 prefix.
B
The OSPF route to 10.60.4.0/24
Why wrong: This is wrong because the /24 is less specific than the /28.
C
The EIGRP route to 10.60.0.0/16
Why wrong: This is wrong because the /16 is broader than both other matches.
D
No route at all
Why wrong: This is wrong because the destination clearly matches all three shown prefixes.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The static route to 10.60.4.16/28
The route used will be the route with the longest matching prefix. In practical terms, 10.60.4.17 falls inside the /28 route shown, and that is more specific than the broader /24 and /16 alternatives. Because specificity comes first, the /28 route wins.
This is a clean route-table interpretation problem that mirrors actual exam-style thinking very closely.
Key principle: Longest prefix match in routing
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 static route to 10.60.4.16/28
Why this is correct
This is correct because the destination falls inside the more specific /28 prefix.
Related concept
Longest prefix match in routing
✗
The OSPF route to 10.60.4.0/24
Why it's wrong here
This is wrong because the /24 is less specific than the /28.
When this WOULD be correct
If the question asked which route would be used for a destination within the 10.60.4.0/24 subnet without a more specific static route, then the OSPF route to 10.60.4.0/24 would be the correct answer, as it would be the best match for any address in that range.
✗
The EIGRP route to 10.60.0.0/16
Why it's wrong here
This is wrong because the /16 is broader than both other matches.
When this WOULD be correct
If the question asked which route would be used if the static route to 10.60.4.16/28 were removed, then the EIGRP route to 10.60.0.0/16 would be the correct answer, as it would be the next best match for the destination.
✗
No route at all
Why it's wrong here
This is wrong because the destination clearly matches all three shown prefixes.
When this WOULD be correct
In a scenario where the routing table has been cleared or all routes have been removed, a question could ask if there are any routes available for destination 10.60.4.17. In this case, the correct answer would be 'No route at all' as there would be no valid paths to the destination.
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.
✓The static route to 10.60.4.16/28Correct answer▾
Why this is correct
This is correct because the destination falls inside the more specific /28 prefix.
✗The OSPF route to 10.60.4.0/24Wrong answer — click to see why▾
Why this is wrong here
This option is wrong because the OSPF route to 10.60.4.0/24 does not directly match the destination 10.60.4.17, which falls under the static route to 10.60.4.16/28. OSPF would not be preferred if a more specific static route exists.
★ When this WOULD be the correct answer
If the question asked which route would be used for a destination within the 10.60.4.0/24 subnet without a more specific static route, then the OSPF route to 10.60.4.0/24 would be the correct answer, as it would be the best match for any address in that range.
Why candidates choose this
Candidates might choose this option due to a misunderstanding of OSPF's role in routing, believing that OSPF routes are always preferred over static routes, especially when they see a broader subnet that includes the destination.
✗The EIGRP route to 10.60.0.0/16Wrong answer — click to see why▾
Why this is wrong here
The EIGRP route to 10.60.0.0/16 is not used for the destination 10.60.4.17 because it does not match the more specific subnet of 10.60.4.16/28, which is preferred in routing decisions.
★ When this WOULD be the correct answer
If the question asked which route would be used if the static route to 10.60.4.16/28 were removed, then the EIGRP route to 10.60.0.0/16 would be the correct answer, as it would be the next best match for the destination.
Why candidates choose this
Candidates may choose this option due to familiarity with EIGRP and its broader subnet coverage, mistakenly believing it would be preferred over a more specific static route.
✗No route at allWrong answer — click to see why▾
Why this is wrong here
This option is wrong because there is a valid static route to the destination 10.60.4.17 via the static route to 10.60.4.16/28, making it reachable. Therefore, stating 'no route at all' is incorrect in this context.
★ When this WOULD be the correct answer
In a scenario where the routing table has been cleared or all routes have been removed, a question could ask if there are any routes available for destination 10.60.4.17. In this case, the correct answer would be 'No route at all' as there would be no valid paths to the destination.
Why candidates choose this
Candidates may choose this option due to a misunderstanding of the routing table's contents or a lack of familiarity with static versus dynamic routes, leading them to believe that if a specific route isn't mentioned, none exist.
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
Remember, the longest prefix match rule is crucial; don't assume broader prefixes are better.
Trap categories for this question
Command / output trap
This is wrong because the destination clearly matches all three shown prefixes.
Detailed technical explanation
How to think about this question
Routing decisions in Cisco devices prioritize the longest prefix match when multiple routes to the same destination exist. This means the route with the most specific subnet mask (largest subnet mask length) is chosen first. In this scenario, the destination IP 10.60.4.17 falls within the 10.60.4.16/28 subnet, which covers IP addresses from 10.60.4.16 to 10.60.4.31. Although there are other routes like 10.60.4.0/24 (OSPF) and 10.60.0.0/16 (EIGRP), these have shorter prefix lengths (/24 and /16 respectively), making them less specific. The static route with the /28 mask is therefore the best match and will be installed in the routing table as the active route. This behavior is fundamental to IP routing and ensures traffic is forwarded along the most precise path available. Administrative distance and routing protocol metrics only come into play when prefix lengths are equal.
KKey Concepts to Remember
Longest prefix match in routing
Static route specificity versus dynamic routing protocols
Subnet mask length impact on route selection
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
Longest prefix match in routing
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.
IP Routing — This question tests IP Routing — Longest prefix match in routing.
What is the correct answer to this question?
The correct answer is: The static route to 10.60.4.16/28 — The route used will be the route with the longest matching prefix. In practical terms, 10.60.4.17 falls inside the /28 route shown, and that is more specific than the broader /24 and /16 alternatives. Because specificity comes first, the /28 route wins.
This is a clean route-table interpretation problem that mirrors actual exam-style thinking very closely.
What should I do if I get this 200-301 question wrong?
Review longest prefix match in routing, then practise related 200-301 questions on the same topic to reinforce the concept.
What is the key concept behind this question?
Longest prefix match in routing
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