Question 319 of 1,389
CCNA IP Routing Practice Question
A router has routes to 10.50.0.0/16, 10.50.10.0/24, and 10.50.10.128/25. Which route is used for traffic to 10.50.10.140?
⚠ Common exam trap
A frequent exam trap is choosing a less specific route such as 10.50.0.0/16 or 10.50.10.0/24 because they also include the destination IP address. Candidates might overlook the importance of the subnet mask length and assume any matching route is acceptable. This mistake ignores the longest-prefix match rule, which always prefers the route with the most bits matching the destination IP. Selecting a broader route leads to incorrect routing decisions and fails to reflect Cisco’s routing behavior.
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
✓
10.50.10.128/25
The /25 route is used because it is the most specific matching prefix. In practical terms, 10.50.10.140 belongs to the upper half of the 10.50.10.0/24 space, which is exactly what 10.50.10.128/25 describes. Even though the /24 and /16 also match, longest-prefix match prefers the narrowest route. This is a direct route-selection question. It reinforces that the router chooses the route that describes the destination most precisely.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
10.50.0.0/16
Why it's wrong here
The longest prefix match rule dictates that 10.50.10.128/25, with a 25-bit mask, is selected for 10.50.10.140 because it offers the most specific match. The /16 route is tempting because it summarises the entire 10.50.0.0 block and would be used for any address within that range if no longer-prefix route existed, such as for a destination like 10.50.20.1.
When this WOULD be correct
In a different scenario where the router only has the route 10.50.0.0/16 available and no more specific routes exist for the 10.50.10.0 subnet, traffic to 10.50.10.140 would use this route due to its broader coverage.
- ✗
10.50.10.0/24
Why it's wrong here
The longest prefix match rule dictates that 10.50.10.128/25, with a 25-bit mask, is selected for 10.50.10.140 because it offers the most specific match. 10.50.10.0/24 is tempting because it does contain the destination address within its range, and it would be the correct choice if no more specific route, such as the /25, existed in the routing table.
When this WOULD be correct
In a different scenario where the question specifies that the router only has the routes 10.50.0.0/16 and 10.50.10.0/24, and traffic to 10.50.10.140 is being routed without any more specific routes, option B would be correct as it would be the best match available.
- ✓
10.50.10.128/25
Why this is correct
This is correct because .140 falls inside the 10.50.10.128/25 range.
- ✗
The default route
Why it's wrong here
This is wrong because more specific matching routes exist.
When this WOULD be correct
If the question specified that the router had no specific routes for the 10.50.10.140 address and only had a default route configured, then the correct answer would be the default route. For example, 'What route will be used if the only available route is the default route?'
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.
✓10.50.10.128/25Correct answer▾
Why this is correct
This is correct because .140 falls inside the 10.50.10.128/25 range.
✗10.50.0.0/16Wrong answer — click to see why▾
Why this is wrong here
The route 10.50.0.0/16 has a prefix length of 16, which is less specific than the /24 and /25 routes. Since 10.50.10.140 falls within the more specific /24 and /25 ranges, the router will use the longest prefix match, not the /16.
★ When this WOULD be the correct answer
In a different scenario where the router only has the route 10.50.0.0/16 available and no more specific routes exist for the 10.50.10.0 subnet, traffic to 10.50.10.140 would use this route due to its broader coverage.
Why candidates choose this
Students might think that because 10.50.10.140 is within the 10.50.0.0/16 range, the /16 route would be used. However, they forget that routers always prefer the most specific (longest prefix) match.
✗10.50.10.0/24Wrong answer — click to see why▾
Why this is wrong here
The route 10.50.10.0/24 has a prefix length of 24, which is less specific than the /25 route. Since 10.50.10.140 falls within the 10.50.10.128/25 range, the /25 route is more specific and will be preferred.
★ When this WOULD be the correct answer
In a different scenario where the question specifies that the router only has the routes 10.50.0.0/16 and 10.50.10.0/24, and traffic to 10.50.10.140 is being routed without any more specific routes, option B would be correct as it would be the best match available.
Why candidates choose this
Students may see that 10.50.10.140 is within the 10.50.10.0/24 range and assume the /24 route is the best match, overlooking the existence of a more specific /25 route that also matches.
✗The default routeWrong answer — click to see why▾
Why this is wrong here
A default route (0.0.0.0/0) is only used when no other more specific route matches the destination. Since there are matching routes (10.50.10.0/24 and 10.50.10.128/25) for 10.50.10.140, the default route is not considered.
★ When this WOULD be the correct answer
If the question specified that the router had no specific routes for the 10.50.10.140 address and only had a default route configured, then the correct answer would be the default route. For example, 'What route will be used if the only available route is the default route?'
Why candidates choose this
Students might think that if a destination is not explicitly listed, the default route is used. However, here there are explicit matching routes, so the default route is not applicable.
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.
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Last reviewed: May 17, 2026
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.
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