CCNA IP Routing Practice Question
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?
⚠ Common exam trap
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.
Answer choices
Why each option matters
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.
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 OSPF route 172.16.10.0/24 also covers 172.16.10.200, yet its prefix length of 24 bits is shorter than the /25 static route. Although OSPF has a lower administrative distance (110) than the static route (1), the longest-match rule takes priority over administrative distance when multiple routes match the same destination. Thus the /24 route loses to the more specific /25 route.
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
The static route to 172.16.10.128/25 is selected because it offers the longest prefix match (25 bits) for the destination 172.16.10.200, which lies within the 172.16.10.128–172.16.10.255 range. Cisco routers always prefer the route with the greatest number of matching bits, so this /25 route outranks the /24 and /16 OSPF routes and the default route, regardless of administrative distance or metric. Traffic is therefore forwarded to next-hop 10.1.1.6.
- ✗
O 172.16.0.0/16 via 10.1.1.10
Why it's wrong here
The OSPF route 172.16.0.0/16 aggregates a very broad range from 172.16.0.0 to 172.16.255.255, so it does include the destination, but with only 16 matching bits it is the least specific of all matching routes. A router will always choose the route with the longest prefix length; therefore this /16 route is never selected as long as the /24 and /25 routes exist in the routing table. It would only be used if the more specific routes were removed or the destination fell outside their ranges.
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
The default route S* 0.0.0.0/0 is a candidate default with a prefix length of zero, meaning it matches every IP address, but it is only used when no longer-prefix route matches the destination. Because the /25 static route already matches 172.16.10.200, the router will ignore the default route for this traffic. The asterisk indicates the route is a valid default candidate, not that it takes precedence over more specific matches.
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
The static route to 172.16.10.128/25 is selected because it offers the longest prefix match (25 bits) for the destination 172.16.10.200, which lies within the 172.16.10.128–172.16.10.255 range. Cisco routers always prefer the route with the greatest number of matching bits, so this /25 route outranks the /24 and /16 OSPF routes and the default route, regardless of administrative distance or metric. Traffic is therefore forwarded to next-hop 10.1.1.6.
✗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?”
Visual reference
Quick reference
Routing Protocol Comparison
| Protocol | Metric | Max Hops | Algorithm | Type |
|---|---|---|---|---|
| RIP v2 | Hop count | 15 | Bellman-Ford | Distance vector |
| OSPF | Cost (bandwidth) | Unlimited | Dijkstra (SPF) | Link state |
| EIGRP | Composite metric | Unlimited | DUAL | Hybrid |
| IS-IS | Cost | Unlimited | Dijkstra | Link state |
| BGP | Policy / attributes | Unlimited | Path vector | Path vector |
RIP's 15-hop limit makes it unsuitable for large networks. OSPF and EIGRP dominate modern enterprise deployments.
Go deeper
Related to this question
Learn chapter
Interpreting HSRP and VRRP Operational Status
Key term
Subnet
A subnet is a logical subdivision of an IP network, created by partitioning a larger network address space using subnet masks.
Key term
Route
A route is a path that data takes through a network from one device or network to another, determined by routing protocols and configured rules.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 200-301 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 200-301 exam.