Question 1hardmultiple choice
Full question →hardmultiple choiceObjective-mapped
A packet is destined for 192.168.40.130. The routing table contains 192.168.40.0/24, 192.168.40.128/25, and 0.0.0.0/0. Which route is 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
Distractor review
192.168.40.0/24
This is wrong because the /24 is less specific than the matching /25 route.
B
Best answer
192.168.40.128/25
This is correct because 192.168.40.130 falls within that more specific range.
C
Distractor review
0.0.0.0/0
This is wrong because the default route is used only when no more specific match exists.
D
Distractor review
No route can be used because the entries overlap
This is wrong because overlapping prefixes are normal and longest-prefix match resolves the choice.
Common exam trap
Common exam trap: answer the scenario, not the keyword
A common exam trap is assuming that the default route or a larger subnet like /24 will be chosen over a more specific subnet like /25. Candidates may incorrectly think the default route is preferred or that overlapping routes cause ambiguity. However, routers always use the longest prefix match rule, which means the route with the most specific subnet mask that includes the destination IP is selected. Misunderstanding subnet mask lengths or ignoring longest prefix match leads to wrong answers in routing questions.
Technical deep dive
How to think about this question
Routing tables use prefix matching to determine the best path for forwarding packets. Each route entry includes a network prefix and a subnet mask, defining a range of IP addresses. When a packet arrives, the router compares the destination IP against all prefixes in the routing table and selects the route with the longest matching prefix, also known as the most specific route. This process ensures that packets are forwarded along the most precise path available. In this question, the destination IP 192.168.40.130 matches both 192.168.40.0/24 and 192.168.40.128/25 prefixes. The /25 subnet mask covers addresses from 192.168.40.128 to 192.168.40.255, which includes 192.168.40.130, while the /24 covers 192.168.40.0 to 192.168.40.255. Because /25 has a longer prefix length (more bits fixed), the router prefers this route over the /24. The default route 0.0.0.0/0 is only used if no more specific match exists. A common exam trap is misunderstanding overlapping routes and default routes. Overlapping prefixes are normal in routing tables, and routers always choose the longest prefix match, not the first or the default route. Misreading the subnet mask length or assuming the default route is preferred can lead to incorrect answers. Practically, this behavior allows routers to implement hierarchical and summarized routing efficiently, forwarding packets to the most specific known network segment.
KKey Concepts to Remember
- A router selects the route with the longest prefix match when multiple routes match a destination IP address.
- Subnet masks define the specificity of a route; longer subnet masks represent more specific routes.
- The default route 0.0.0.0/0 is used only when no other more specific route matches the destination IP.
- Overlapping route entries in a routing table are normal and resolved by choosing the most specific prefix.
- Routing decisions rely on prefix length before considering administrative distance or metrics.
- A /25 subnet mask covers half of a /24 network, making it more specific for addresses within its range.
- Routers do not prefer familiar or larger networks over more specific smaller subnets during route selection.
- Longest prefix match routing ensures efficient and accurate packet forwarding in hierarchical IP networks.
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 router selects the route with the longest prefix match when multiple routes match a destination IP address.
What is the correct answer to this question?
The correct answer is: 192.168.40.128/25 — The /25 route is used because it is the most specific matching prefix. In plain language, even though the /24 and the default route also technically match, the router prefers the entry that most precisely describes the destination range. Since 192.168.40.130 falls inside 192.168.40.128/25, that route wins under longest-prefix match. This is a classic routing-table interpretation pattern. The router does not start with the default route when more specific routes exist, and it does not choose the /24 simply because it is familiar. Specificity comes first.
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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