Question 1hardmultiple choice
Full question →hardmultiple choiceObjective-mapped
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. A packet is destined for 10.1.1.130. 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
The OSPF 10.1.1.0/24 route
It matches, but there is a more specific /25 route.
B
Best answer
The static 10.1.1.128/25 route
Longest-prefix match sends 10.1.1.130 to the /25.
C
Distractor review
The default route
The default route is used only when no more specific route exists.
D
Distractor review
The router load-balances across all three
These routes have different prefix lengths.
Common exam trap
Common exam trap: answer the scenario, not the keyword
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.
Technical deep dive
How to think about this question
Routing tables in Cisco routers contain multiple routes to various destinations, each with a prefix and prefix length that defines the network size. The router uses the longest-prefix match rule to select the most specific route for forwarding packets. A longer prefix length (larger subnet mask) means a more specific route, which takes precedence over less specific routes with shorter prefix lengths. This ensures packets are routed optimally to the most precise destination network. When a packet arrives, the router compares the destination IP address against all routes in its routing table. It selects the route with the longest matching prefix. In this scenario, the destination 10.1.1.130 matches both the 10.1.1.0/24 OSPF route and the 10.1.1.128/25 static route. Since /25 is a longer prefix than /24, the static route is preferred regardless of routing protocol or administrative distance. Default routes (0.0.0.0/0) are only used if no more specific route exists. A common exam trap is to assume routing protocol preference or administrative distance overrides longest-prefix match. However, Cisco routers always apply longest-prefix match first, then use administrative distance to break ties between routes of equal prefix length. Practically, this means a static /25 route will be chosen over an OSPF /24 route for the same destination. Understanding this behavior prevents mistakes in subnetting and routing questions, especially when multiple routes overlap in the routing table.
KKey Concepts to Remember
- Cisco routers use the longest-prefix match rule to select the most specific route for forwarding packets based on subnet mask length.
- A route with a longer prefix length (e.g., /25) is preferred over a route with a shorter prefix length (e.g., /24) regardless of routing protocol.
- Static routes are installed in the routing table and can override dynamic routing protocol routes if they have a more specific prefix.
- Default routes (0.0.0.0/0) are only used when no other more specific route matches the destination IP address.
- Routing protocols like OSPF advertise routes, but the router still applies longest-prefix match before considering administrative distance or metrics.
- Administrative distance is used only to choose between routes with the same prefix length, not to override longest-prefix match.
- Routers do not load-balance across routes with different prefix lengths because longest-prefix match selects a single best route.
- Understanding subnetting and prefix lengths is critical to correctly interpreting routing table entries and route selection.
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?
Cisco routers use the longest-prefix match rule to select the most specific route for forwarding packets based on subnet mask length.
What is the correct answer to this question?
The correct answer is: 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.
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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