Question 1mediummulti select
Full question →mediummulti selectObjective-mapped
Which two statements accurately describe longest-prefix match?
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 most specific matching route is preferred over broader matching routes.
This is correct because specificity is the core rule in longest-prefix match.
B
Best answer
A /24 is more specific than a /16.
This is correct because the longer prefix describes a narrower destination range.
C
Distractor review
The default route is always preferred over a matching specific route.
This is wrong because the default route is used only when no more specific route matches.
D
Distractor review
Administrative distance replaces the need for longest-prefix match.
This is wrong because administrative distance and longest-prefix match serve different purposes.
E
Distractor review
A /16 is more specific than a /24.
This is wrong because the opposite is true.
Common exam trap
Common exam trap: answer the scenario, not the keyword
A frequent exam trap is assuming that the default route (0.0.0.0/0) is preferred over more specific routes. Many candidates mistakenly believe the default route is always the first choice, but in reality, it is the least specific and only used when no other matching route exists. Another trap is confusing administrative distance with longest-prefix match; administrative distance only applies when choosing between routes learned from different sources, not when selecting the most specific prefix. Misunderstanding these concepts can lead to incorrect answers about routing behavior in Cisco devices.
Technical deep dive
How to think about this question
Longest-prefix match is a fundamental routing principle used by Cisco routers to determine the best path for forwarding IP packets. When multiple routes in the routing table match a destination IP address, the router selects the route with the longest subnet mask, meaning the most specific prefix. This ensures that traffic is forwarded along the most precise path available, optimizing routing efficiency and accuracy. The decision process for longest-prefix match involves comparing the prefix lengths of all matching routes. For example, a /24 prefix (255.255.255.0) covers fewer IP addresses than a /16 prefix (255.255.0.0), making the /24 route more specific. The router always prefers the route with the longest prefix length, regardless of other factors like administrative distance or metric, unless no matching route exists. The default route (0.0.0.0/0) is the least specific and is only used when no other route matches. A common exam trap is confusing longest-prefix match with administrative distance or assuming the default route is preferred over specific routes. Administrative distance is used to choose between routes learned from different routing protocols but does not override prefix specificity. In practical networking, understanding longest-prefix match prevents misrouting and ensures that traffic follows the intended path, especially in complex networks with overlapping subnets or multiple routing sources.
KKey Concepts to Remember
- Longest-prefix match means a router prefers the route with the most specific subnet mask that matches the destination IP address.
- A route with a longer prefix length (e.g., /24) describes a narrower range of IP addresses than a shorter prefix length (e.g., /16).
- The default route (0.0.0.0/0) is the least specific and is only used when no more specific route exists in the routing table.
- Administrative distance is used to select between routes from different routing protocols but does not replace longest-prefix match.
- Routers perform longest-prefix match before considering administrative distance or metric values when forwarding packets.
- A more specific route installed in the routing table overrides broader routes for the same destination network.
- Longest-prefix match ensures efficient and accurate routing by directing traffic to the most precise next-hop available.
- Confusing route specificity with route trustworthiness or default route preference is a common mistake in routing decisions.
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?
Longest-prefix match means a router prefers the route with the most specific subnet mask that matches the destination IP address.
What is the correct answer to this question?
The correct answer is: The most specific matching route is preferred over broader matching routes. — Longest-prefix match means the router prefers the most specific route that matches the destination. In plain language, if several routes could all work, the router chooses the one that describes the destination range most precisely. That is why a /25 wins over a /24, and a /24 wins over a /16, when all of them match the same destination. This is a foundational routing rule. The wrong answers usually confuse route specificity with route-source trust or assume the default route is considered first. The two correct answers are the ones that keep the focus on specificity.
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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