Question 1mediummultiple choice
Full question →mediummultiple choiceObjective-mapped
R1 receives an OSPF route to 10.55.0.0/16 and already has a static route to 10.55.10.0/24. Which route will be used for traffic sent to 10.55.10.25?
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
Distractor review
The OSPF /16 route, because dynamic routes override static routes learned later.
Dynamic routes do not override a more specific route just because they are dynamic.
B
Best answer
The static /24 route, because it is the longest-prefix match.
Route lookup prefers the most specific matching prefix.
C
Distractor review
Both routes equally, because they point to the same major network.
Major network boundaries do not create equal-cost behavior.
D
Distractor review
Neither route, because overlapping routes are invalid.
Overlapping routes are normal in IP routing.
Common exam trap
Common exam trap: answer the scenario, not the keyword
A frequent exam trap is believing that dynamic routing protocols like OSPF always override static routes because they are learned dynamically. This misconception leads to choosing the broader OSPF /16 route instead of the more specific static /24 route. The trap ignores the fundamental longest-prefix match rule, which dictates that the router selects the most specific route regardless of whether it is static or dynamic. Additionally, some candidates confuse administrative distance as the primary factor even when prefix lengths differ, which is incorrect. Understanding that prefix specificity takes precedence prevents this mistake.
Technical deep dive
How to think about this question
Routing decisions in Cisco devices rely primarily on the longest-prefix match rule, which means the router selects the route with the most specific subnet mask that matches the destination IP address. In this scenario, R1 has two routes: an OSPF-learned route to 10.55.0.0/16 and a static route to 10.55.10.0/24. Since 10.55.10.25 falls within both prefixes, the router compares the subnet masks and prefers the /24 static route because it is more specific than the /16 OSPF route. Administrative distance (AD) is a secondary factor used only when two routes have the exact same prefix length. AD ranks route sources by trustworthiness, with static routes typically having a lower AD (higher trust) than OSPF routes. However, because the static route here is more specific, the router does not need to compare AD values. The longest-prefix match rule always takes precedence over AD when prefixes differ in length. A common exam trap is to assume dynamic routing protocols like OSPF always override static routes because they are learned dynamically. This is incorrect because Cisco routers prioritize the most specific route first. In practical networking, overlapping routes are normal and essential for route summarization and policy routing. Understanding this behavior helps avoid misconfigurations and ensures predictable routing outcomes.
KKey Concepts to Remember
- Cisco routers use the longest-prefix match rule to select the most specific route that matches the destination IP address.
- Static routes have a default administrative distance of 1, which is lower than OSPF's default of 110, making static routes more trusted when prefix lengths are equal.
- When multiple routes to the same destination exist, the router first compares prefix lengths before considering administrative distance.
- OSPF advertises routes dynamically with a default administrative distance of 110, but it does not override more specific static routes.
- Overlapping routes with different subnet masks are valid and common in IP routing to allow granular traffic forwarding.
- Route lookup in Cisco IOS always prefers the route with the longest subnet mask, regardless of whether the route is static or dynamic.
- Administrative distance is only compared when two routes have the same prefix length and destination network.
- Static routes provide precise control over routing decisions and can override dynamic routes if they are more specific.
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 that matches the destination IP address.
What is the correct answer to this question?
The correct answer is: The static /24 route, because it is the longest-prefix match. — The static /24 route is more specific than the OSPF /16 route, so longest-prefix match wins. Administrative distance is only compared among routes to the same prefix length.
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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