The answer is the route S 172.16.10.128/25 via 10.1.1.6. This is correct because the router uses the longest prefix match rule when selecting a path for traffic destined to 172.16.10.200; among all matching routes, the one with the most specific subnet mask—the /25—takes priority over a less specific /24 or any other broader route. On the CCNA 200-301 v2 exam, this concept tests your ability to evaluate prefix boundaries before considering administrative distance or metric, as a common trap is to jump to a route with a lower metric from a different protocol without first verifying the subnet containment. For 172.16.10.200, the /25 covers addresses 172.16.10.128 through 172.16.10.255, which includes the destination, while a /24 would also match but is less specific. Remember the memory tip: “The longer the mask, the stronger the grasp”—always check the prefix length first, and only then consider other tiebreakers.
CCNA IP Routing Practice Question
This 200-301 practice question tests your understanding of ip routing. 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. A key principle to apply: a Cisco router selects the route with the longest prefix match to forward traffic to a destination IP address.. 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 172.16.10.0/24 [110/20] via 10.1.1.2
S 172.16.10.128/25 [1/0] via 10.1.1.6
O 172.16.0.0/16 [110/30] via 10.1.1.10
S* 0.0.0.0/0 [1/0] via 203.0.113.1
A router has these routes installed. Which path will be chosen for traffic to 172.16.10.200?
R1# show ip route
O 172.16.10.0/24 [110/20] via 10.1.1.2
S 172.16.10.128/25 [1/0] via 10.1.1.6
O 172.16.0.0/16 [110/30] via 10.1.1.10
S* 0.0.0.0/0 [1/0] via 203.0.113.1
A
O 172.16.10.0/24 via 10.1.1.2
Why wrong: This is wrong because the /24 matches, but the /25 is more specific and also matches the destination.
B
S 172.16.10.128/25 via 10.1.1.6
This is correct because 172.16.10.200 falls within the 172.16.10.128/25 range, making it the most specific matching route.
C
O 172.16.0.0/16 via 10.1.1.10
Why wrong: This is wrong because the /16 is broader than both the /24 and the /25 and will not be preferred when a more specific match exists.
D
S* 0.0.0.0/0 via 203.0.113.1
Why wrong: This is wrong because a default route is used only when there is no more specific match available.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
S 172.16.10.128/25 via 10.1.1.6
When multiple routes could match a destination, the router first uses longest-prefix match. In plain language, it chooses the route that describes the destination most specifically, not simply the one from the protocol with the lowest metric somewhere else in the table. For 172.16.10.200, the key is to determine which listed prefix actually contains that address and is the narrowest valid match.
If a /25 and a /24 both match, the /25 wins because it is more specific. If the destination does not fit inside the smaller subnet, then the broader route is used instead. That is the entire skill being tested here: careful evaluation of the prefix boundaries before thinking about anything else. Once you recognize the address falls within the upper half of the /24, the more specific route becomes obvious.
Key principle: A Cisco router selects the route with the longest prefix match to forward traffic to a destination IP address.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
O 172.16.10.0/24 via 10.1.1.2
Why it's wrong here
This is wrong because the /24 matches, but the /25 is more specific and also matches the destination.
When this WOULD be correct
In a different question where the destination IP was 172.16.10.50, option A would be correct as it matches the subnet 172.16.10.0/24. The question would need to specify that the destination IP is within this range for option A to be valid.
✓
S 172.16.10.128/25 via 10.1.1.6
Why this is correct
This is correct because 172.16.10.200 falls within the 172.16.10.128/25 range, making it the most specific matching route.
Related concept
A Cisco router selects the route with the longest prefix match to forward traffic to a destination IP address.
✗
O 172.16.0.0/16 via 10.1.1.10
Why it's wrong here
This is wrong because the /16 is broader than both the /24 and the /25 and will not be preferred when a more specific match exists.
When this WOULD be correct
In a different scenario, if the question asked for the best route to any IP within the 172.16.0.0/16 network without requiring specificity, then option C would be correct as it encompasses a broader range of addresses, including 172.16.10.200.
✗
S* 0.0.0.0/0 via 203.0.113.1
Why it's wrong here
This is wrong because a default route is used only when there is no more specific match available.
When this WOULD be correct
In a different scenario where the question asks which route should be used for traffic when no specific route exists for the destination, option D would be correct as it would serve as the default route for all unmatched traffic.
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.
✓S 172.16.10.128/25 via 10.1.1.6Correct answer▾
Why this is correct
This is correct because 172.16.10.200 falls within the 172.16.10.128/25 range, making it the most specific matching route.
✗O 172.16.10.0/24 via 10.1.1.2Wrong answer — click to see why▾
Why this is wrong here
Option A is incorrect because the subnet 172.16.10.0/24 does not encompass the IP address 172.16.10.200, which falls within the subnet 172.16.10.128/25. The correct route must match the specific subnet that includes the destination IP.
★ When this WOULD be the correct answer
In a different question where the destination IP was 172.16.10.50, option A would be correct as it matches the subnet 172.16.10.0/24. The question would need to specify that the destination IP is within this range for option A to be valid.
Why candidates choose this
Candidates may choose option A due to its familiarity with classful addressing and the assumption that a broader subnet (like /24) could cover more addresses, leading to confusion in subnet matching.
✗O 172.16.0.0/16 via 10.1.1.10Wrong answer — click to see why▾
Why this is wrong here
Option C is wrong because the route 172.16.0.0/16 does not match the specific destination IP 172.16.10.200 as closely as the more specific route 172.16.10.128/25 does, which is selected due to its longer prefix length.
★ When this WOULD be the correct answer
In a different scenario, if the question asked for the best route to any IP within the 172.16.0.0/16 network without requiring specificity, then option C would be correct as it encompasses a broader range of addresses, including 172.16.10.200.
Why candidates choose this
Candidates might choose option C because it represents a larger subnet that includes the target IP, leading them to mistakenly believe it is a valid choice due to its broader coverage.
✗S* 0.0.0.0/0 via 203.0.113.1Wrong answer — click to see why▾
Why this is wrong here
Option D is incorrect because it represents a default route (0.0.0.0/0) that would not specifically match the destination IP 172.16.10.200, which falls under the more specific route of 172.16.10.128/25.
★ When this WOULD be the correct answer
In a different scenario where the question asks which route should be used for traffic when no specific route exists for the destination, option D would be correct as it would serve as the default route for all unmatched traffic.
Why candidates choose this
Candidates may choose this option because they recognize the default route as a common fallback for routing, leading them to mistakenly believe it could apply to any unmatched destination, including specific IPs.
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 to select a route based solely on the routing protocol type or administrative distance without verifying the subnet mask specificity. For example, candidates might incorrectly choose the OSPF-learned /24 route over the static /25 route because they assume dynamic routes are preferred or because they overlook the subnet boundaries. This mistake ignores the fundamental longest-prefix match rule, which always prioritizes the most specific subnet regardless of protocol. Misreading subnet ranges or confusing the address boundaries of a /25 versus a /24 can also lead to choosing an incorrect route.
Detailed technical explanation
How to think about this question
Routing decisions in Cisco routers rely heavily on the concept of longest-prefix match, which means the router selects the route with the most specific subnet mask that includes the destination IP address. In this scenario, the router has multiple routes to the 172.16.10.0 network with different subnet masks: a /16, a /24, and a /25. The /25 subnet is the most specific because it covers a smaller range of IP addresses, allowing the router to forward traffic more precisely.
When a packet destined for 172.16.10.200 arrives, the router evaluates each route to see which subnet contains this IP. The /25 subnet 172.16.10.128/25 covers IP addresses from 172.16.10.128 to 172.16.10.255, which includes 172.16.10.200. Although the /24 and /16 routes also cover this address, the router prefers the /25 route due to its longer prefix length, ensuring more accurate routing. This behavior is fundamental in Cisco routing and is consistent across routing protocols and static routes.
A common exam trap is to overlook the subnet boundaries and assume that a broader subnet like /24 or /16 will be chosen simply because it appears first or is learned via a routing protocol like OSPF. However, Cisco routers always prioritize the most specific route regardless of the routing protocol or administrative distance when multiple matches exist. Practically, this ensures traffic is routed optimally and prevents suboptimal routing paths that could cause inefficiencies or routing loops.
KKey Concepts to Remember
A Cisco router selects the route with the longest prefix match to forward traffic to a destination IP address.
Subnet masks with more bits set (longer prefixes) represent more specific routes and are preferred over broader subnets.
Static routes (S) and OSPF routes (O) are compared based on prefix length first before considering administrative distance or metric.
The router includes a destination IP in a subnet if the IP falls within the subnet's address range defined by the prefix length.
Default routes (0.0.0.0/0) are only used when no more specific route matches the destination IP address.
Routing protocols advertise routes with varying prefix lengths, but the router always prefers the most specific matching route.
Ignoring subnet boundaries can lead to selecting less optimal routes, which is a common exam trap in routing questions.
The longest prefix match rule ensures efficient and accurate routing by narrowing down the forwarding path to the smallest subnet.
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 Cisco router selects the route with the longest prefix match to forward traffic to a destination IP address.
Real-world example
How this comes up in practice
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.
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 Cisco router selects the route with the longest prefix match to forward traffic to a destination IP address., then practise related 200-301 questions on the same topic to reinforce the concept.
IP Routing — This question tests IP Routing — A Cisco router selects the route with the longest prefix match to forward traffic to a destination IP address..
What is the correct answer to this question?
The correct answer is: S 172.16.10.128/25 via 10.1.1.6 — When multiple routes could match a destination, the router first uses longest-prefix match. In plain language, it chooses the route that describes the destination most specifically, not simply the one from the protocol with the lowest metric somewhere else in the table. For 172.16.10.200, the key is to determine which listed prefix actually contains that address and is the narrowest valid match.
If a /25 and a /24 both match, the /25 wins because it is more specific. If the destination does not fit inside the smaller subnet, then the broader route is used instead. That is the entire skill being tested here: careful evaluation of the prefix boundaries before thinking about anything else. Once you recognize the address falls within the upper half of the /24, the more specific route becomes obvious.
What should I do if I get this 200-301 question wrong?
Review a Cisco router selects the route with the longest prefix match to forward traffic to a destination IP address., then practise related 200-301 questions on the same topic to reinforce the concept.
What is the key concept behind this question?
A Cisco router selects the route with the longest prefix match to forward traffic to a destination IP address.
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