CCNA IP Routing Practice Question
Exhibit
O 10.1.1.0/24 via 192.0.2.1 S 10.1.1.128/25 via 198.51.100.1 S* 0.0.0.0/0 via 203.0.113.1
Exhibit: A router has the following routes in its routing table: - OSPF: 10.1.1.0/24 - Static: 10.1.1.128/25 - Default: 0.0.0.0/0
A packet is destined for 10.1.1.130. Which route does the router use?
⚠ Common exam trap
A common exam trap is to select a route based solely on routing protocol preference or administrative distance without considering prefix length. Many candidates incorrectly choose the OSPF 10.1.1.0/24 route because OSPF is a dynamic protocol and might assume it is preferred over a static route. However, Cisco routers always apply longest-prefix match first, so the static 10.1.1.128/25 route is chosen because it is more specific. Another trap is to think the router load-balances across all routes, but load balancing only occurs among routes with equal prefix length and metric, not across different subnet sizes.
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
✓
The static 10.1.1.128/25 route
Routers use longest-prefix match before they think about metrics. The /25 route for 10.1.1.128/25 is more specific than the /24 or the default route, so traffic for 10.1.1.130 follows that path.
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 OSPF 10.1.1.0/24 route
Why it's wrong here
The OSPF route 10.1.1.0/24 does match the destination, but it describes a broader range of 256 addresses, whereas the static 10.1.1.128/25 describes a narrower range of 128 addresses that still includes the target. Longest-prefix match dictates that the more specific /25 route is preferred over the /24, regardless of the administrative distance or protocol; therefore, the OSPF route is not the one that gets used.
When this WOULD be correct
In a scenario where the question asks which route would be used if the destination IP were 10.1.1.0, the OSPF 10.1.1.0/24 route would be the correct answer, as it matches the entire subnet and is the best match for that specific address.
- ✓
The static 10.1.1.128/25 route
Why this is correct
Although the OSPF route has a lower administrative distance, the destination 10.1.1.130 falls inside the 10.1.1.128/25 range, and the forwarding decision uses longest-prefix-match: the /25 mask represents 128 addresses, while the /24 represents 256, making the /25 the most specific, or longest, prefix that contains the destination. Therefore, the router forwards this packet via the static route, not by any other attribute.
- ✗
The default route
Why it's wrong here
A default route is the ultimate prefix-length of 0.0.0.0/0, the least specific of all possible routes. In the routing table, it is used only when no other route matches the destination; because the /25 and /24 routes both match 10.1.1.130, the default route is never consulted, and even if it were, the /25's longer prefix would still take precedence.
When this WOULD be correct
In a scenario where the router has no specific routes for the destination address and only a default route configured (e.g., 0.0.0.0/0), a packet destined for an unknown address would use the default route. An exam question could specify that no other routes are available for the destination.
- ✗
The router load-balances across all three
Why it's wrong here
Load balancing across equal-cost paths only applies to multiple routes that share the exact same prefix length and destination network. Here, the three candidates are 10.1.1.0/24, 10.1.1.128/25, and 0.0.0.0/0, each with a different prefix length, so they are not competing equal-cost routes; longest-prefix match selects exactly one route, so the router does not distribute the packet across them.
When this WOULD be correct
In a different scenario where multiple equal-cost routes exist for the same destination, and the router is configured to load-balance, this option would be correct. For example, if there were multiple static routes to 10.1.1.130 with the same metric, the router would indeed load-balance traffic across them.
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 10.1.1.128/25 routeCorrect answer▾
Why this is correct
Although the OSPF route has a lower administrative distance, the destination 10.1.1.130 falls inside the 10.1.1.128/25 range, and the forwarding decision uses longest-prefix-match: the /25 mask represents 128 addresses, while the /24 represents 256, making the /25 the most specific, or longest, prefix that contains the destination. Therefore, the router forwards this packet via the static route, not by any other attribute.
✗The OSPF 10.1.1.0/24 routeWrong answer — click to see why▾
Why this is wrong here
The OSPF 10.1.1.0/24 route matches the destination 10.1.1.130, but the router uses the longest-prefix match rule. Since the static 10.1.1.128/25 route has a longer prefix length (25 vs 24), it is more specific and preferred.
★ When this WOULD be the correct answer
In a scenario where the question asks which route would be used if the destination IP were 10.1.1.0, the OSPF 10.1.1.0/24 route would be the correct answer, as it matches the entire subnet and is the best match for that specific address.
Why candidates choose this
Students may think that because the /24 route is learned via OSPF (a dynamic routing protocol) and has a lower administrative distance than a static route, it would be preferred. However, prefix length takes precedence over administrative distance in the forwarding decision.
✗The default routeWrong answer — click to see why▾
Why this is wrong here
The default route (0.0.0.0/0) is only used when no other route matches the destination. Since the destination 10.1.1.130 matches both the /24 and /25 routes, the default route is not considered.
★ When this WOULD be the correct answer
In a scenario where the router has no specific routes for the destination address and only a default route configured (e.g., 0.0.0.0/0), a packet destined for an unknown address would use the default route. An exam question could specify that no other routes are available for the destination.
Why candidates choose this
Students might think that if a default route exists, it will be used as a catch-all. However, the router always checks for more specific matches first; the default route is the last resort.
✗The router load-balances across all threeWrong answer — click to see why▾
Why this is wrong here
Load balancing only occurs when multiple routes have the same prefix length and administrative distance. Here, the routes have different prefix lengths (/24, /25, and /0), so the router selects the single best match based on longest prefix.
★ When this WOULD be the correct answer
In a different scenario where multiple equal-cost routes exist for the same destination, and the router is configured to load-balance, this option would be correct. For example, if there were multiple static routes to 10.1.1.130 with the same metric, the router would indeed load-balance traffic across them.
Why candidates choose this
Students may confuse equal-cost multipath (ECMP) load balancing with the general concept of having multiple routes. They might think that because multiple routes exist, the router will distribute traffic among them, but that only happens when routes are equally specific.
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
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Key term
Packet
A packet is a small unit of data that is sent over a network, containing both the actual data and control information for delivery.
Key term
OSPF
OSPF is a link-state routing protocol that uses the SPF algorithm to compute the shortest path to each destination within a single autonomous system.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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