Question 1hardmultiple choice
Full question →hardmultiple choiceObjective-mapped
Exhibit
R1# show ip route O 10.1.1.0/24 [110/20] via 192.0.2.2, GigabitEthernet0/0 S 10.1.1.128/25 [1/0] via 192.0.2.6 O 10.1.0.0/16 [110/30] via 192.0.2.10, GigabitEthernet0/1 S* 0.0.0.0/0 [1/0] via 198.51.100.1
A packet destined for 10.1.1.130 arrives at the router. Based on the routing table, which route will be used?
Answer choices
Why each option matters
Good practice is not just finding the correct option. The wrong answers often show the exact trap the exam wants you to fall into.
A
Best answer
The static route to 10.1.1.128/25
This is correct because 10.1.1.130 belongs to the 10.1.1.128/25 range, and /25 is the longest matching prefix shown.
B
Distractor review
The default route
This is wrong because a default route is a last resort. Since more specific routes exist, it is not used.
C
Distractor review
The OSPF route to 10.1.1.0/24
This is wrong because although 10.1.1.130 does fall within 10.1.1.0/24, that route is less specific than 10.1.1.128/25.
D
Distractor review
The OSPF route to 10.1.0.0/16
This is wrong because the /16 route is even less specific than the /24.
Common exam trap
Common exam trap: answer the scenario, not the keyword
A frequent exam trap is to mistakenly select the default route or a less specific OSPF route because they appear in the routing table. Candidates often overlook that routers prioritize the longest prefix match before considering administrative distance or route type. This leads to choosing the default route or a broader subnet like 10.1.1.0/24 or 10.1.0.0/16 instead of the more specific static route 10.1.1.128/25. Misunderstanding this can cause incorrect answers and confusion about how Cisco routers forward packets.
Technical deep dive
How to think about this question
Routing decisions in Cisco routers rely primarily on the longest prefix match principle, which means the router selects the route with the most specific subnet mask that includes the destination IP address. In this question, the destination IP 10.1.1.130 falls within multiple routes: 10.1.0.0/16, 10.1.1.0/24, and 10.1.1.128/25. The /25 subnet mask is the longest prefix, making it the most specific route. This specificity ensures packets are forwarded along the most precise path available, optimizing network efficiency and reducing unnecessary hops. When multiple routes match a destination, the router first compares prefix lengths to find the longest match. Only if two or more routes have the same prefix length does the router consider administrative distance and metric to choose the best path. In this scenario, the static route to 10.1.1.128/25 is the most specific, so it is selected regardless of the presence of OSPF routes or the default route. This behavior aligns with Cisco’s routing logic and is critical for understanding route selection in complex routing tables. A common exam trap is to assume the router always prefers routes with the lowest administrative distance or OSPF routes over static routes. However, the router prioritizes prefix length first, not administrative distance, unless prefix lengths tie. Practically, this means a static route with a longer prefix mask will override less specific OSPF routes or default routes. Understanding this hierarchy prevents misinterpretation of routing behavior and ensures accurate troubleshooting and configuration in Cisco networks.
KKey Concepts to Remember
- A Cisco router selects the route with the longest matching prefix to forward packets to the destination IP address.
- When multiple routes match a destination, the router compares prefix lengths before considering administrative distance or metrics.
- Static routes with longer prefix masks override less specific dynamic routes like OSPF or default routes in route selection.
- The default route is only used when no more specific matching routes exist in the routing table.
- OSPF routes are preferred over static routes only if they have the same prefix length and a lower administrative distance.
- Routers install the most specific route in the routing table to optimize packet forwarding efficiency.
- Administrative distance is a secondary factor used only when prefix lengths are identical among multiple routes.
- Misinterpreting routing precedence between prefix length and administrative distance is a common exam mistake.
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.
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More questions from this exam
Keep practising from the same exam bank, or move into a focused topic page if this question exposed a weak area.
Question 1
A router learns the same prefix from both OSPF and EIGRP. Which route is installed by default?
Question 2
A router shows this output: R1#show ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 10.1.1.2 1 FULL/DR 00:00:34 192.168.12.2 GigabitEthernet0/0 10.1.1.3 1 2WAY/DROTHER 00:00:39 192.168.12.3 GigabitEthernet0/0 Which statement is correct?
Question 3
What is the OSPF metric called?
Question 4
A non-root switch has two uplinks toward the root bridge. One path has a lower total STP cost than the other. What role will the lower-cost uplink have?
Question 5
A router interface applies this ACL inbound: 10 deny tcp any any eq 80 20 permit ip any any A user reports that web browsing to a server by IP address fails, but ping works. Which statement best explains the behavior?
Question 6
A router learns route 198.51.100.0/24 from OSPF with AD 110 and also has a static route to the same prefix configured with AD 150. Which route is installed?
FAQ
Questions learners often ask
What does this 200-301 question test?
A Cisco router selects the route with the longest matching prefix to forward packets to the destination IP address.
What is the correct answer to this question?
The correct answer is: The static route to 10.1.1.128/25 — Routers do not choose the route with the lowest administrative distance first when several routes match a destination. They begin with the most specific matching prefix. In practical terms, the router looks for the narrowest route that still contains the destination address. The packet is going to 10.1.1.130. That address fits inside 10.1.1.128/25, and it also fits inside 10.1.1.0/24 and 10.1.0.0/16. But /25 is the most specific of those matches, so the router uses it. Only after determining that two routes have the same prefix length would the router consider administrative distance and metric. The default route is ignored because more specific matches exist.
What should I do if I get this 200-301 question wrong?
Then try more questions from the same exam bank and focus on understanding why the wrong options are tempting.
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