Question 1hardmultiple choice
Full question →hardmultiple choiceObjective-mapped
A router has a default route and a specific route to 203.0.113.0/24. Which route is used for traffic to 203.0.113.25?
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 specific route to 203.0.113.0/24
This is correct because it is more specific than the default route.
B
Distractor review
The default route
This is wrong because the default route is used only when no more specific route matches.
C
Distractor review
Both routes are always load-balanced
This is wrong because that is not the default behavior simply because both routes exist.
D
Distractor review
Neither route because defaults cannot coexist with specific routes
This is wrong because defaults commonly coexist with more specific routes.
Common exam trap
Common exam trap: answer the scenario, not the keyword
A common exam trap is thinking the default route will be used for traffic to 203.0.113.25 simply because it is configured and might have a lower administrative distance or metric. Candidates may overlook that Cisco routers always apply the longest-prefix match rule first, which means the specific 203.0.113.0/24 route takes precedence. This mistake often arises from confusing route preference criteria or assuming default routes override specific routes. Understanding that default routes are fallback options only helps avoid this trap.
Technical deep dive
How to think about this question
Routing in IP networks relies on the principle of longest-prefix match, where a router selects the most specific route available for forwarding packets. A specific route, such as 203.0.113.0/24, defines a precise subnet and matches destination IP addresses within that range. In contrast, a default route (0.0.0.0/0) acts as a catch-all path used only when no more specific route exists. This behavior ensures efficient and accurate packet delivery by prioritizing detailed routing information over generic fallbacks. When a router receives a packet destined for 203.0.113.25, it compares the destination IP against its routing table entries. Since 203.0.113.25 falls within the 203.0.113.0/24 subnet, the router uses the specific route to forward the packet. The default route is ignored in this case because the specific route has a longer prefix length, making it a better match. This decision process is fundamental in Cisco routing and is consistently applied across routing protocols and static routes. A common exam trap is assuming that the default route might be used even when a specific route exists, especially if the default route is configured with a lower administrative distance or metric. However, Cisco routers always apply longest-prefix match first before considering administrative distance or metric. Practically, this means that default routes coexist with specific routes as fallback options, but they never override more precise routes. Understanding this hierarchy prevents misconfiguration and routing errors in real networks.
KKey Concepts to Remember
- A router uses the longest-prefix match rule to select the most specific route for forwarding packets.
- A specific route like 203.0.113.0/24 matches destination IP addresses within that subnet more precisely than a default route.
- The default route 0.0.0.0/0 is used only when no more specific route exists in the routing table.
- Cisco routers always prefer routes with longer subnet masks before considering administrative distance or metric values.
- Default routes commonly coexist with specific routes and serve as fallback paths in routing tables.
- Routing decisions are based first on prefix length, then on administrative distance and metric if multiple routes have the same prefix length.
- A packet destined for 203.0.113.25 matches the 203.0.113.0/24 route because it falls within that subnet range.
- Misunderstanding the precedence of longest-prefix match over default routes is a frequent cause of routing misconfigurations.
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 uses the longest-prefix match rule to select the most specific route for forwarding packets.
What is the correct answer to this question?
The correct answer is: The specific route to 203.0.113.0/24 — The specific route to 203.0.113.0/24 is used because it is a more specific match than the default route. In plain language, even though the default route could technically match almost anything, the router always prefers a route that more precisely describes the destination network. Since 203.0.113.25 is inside 203.0.113.0/24, that route wins under longest-prefix match. This is one of the most basic routing-table interpretation rules. The default route remains important as a fallback, but it is not chosen when a more specific valid route exists.
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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