Question 1hardmultiple choice
Full question →hardmultiple choiceObjective-mapped
Exhibit
R1# show ip route D 10.10.10.0/24 [90/30720] via 192.0.2.2 O 10.10.10.0/24 [110/20] via 192.0.2.6 Destination being tested: 10.10.10.200
Based on the exhibit, why is traffic to 10.10.10.200 using the EIGRP route instead of the OSPF route?
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
Because OSPF can be used only for IPv6 routes.
This is wrong because OSPF is commonly used for IPv4 as well.
B
Best answer
Because EIGRP has a lower administrative distance than OSPF for the same prefix length.
This is correct because both routes are /24, so administrative distance becomes decisive and EIGRP wins.
C
Distractor review
Because OSPF routes are never installed when EIGRP is present.
This is wrong because OSPF routes can still exist in the table even if they are not selected as best.
D
Distractor review
Because EIGRP routes always have a smaller subnet mask than OSPF routes.
This is wrong because route source does not determine the subnet mask length that way.
Common exam trap
Common exam trap: answer the scenario, not the keyword
A common exam trap is to incorrectly assume that OSPF routes always take precedence over EIGRP routes or that the routing protocol alone determines route preference. Candidates may also mistakenly believe that OSPF is only for IPv6 or that EIGRP routes always have smaller subnet masks. These misconceptions lead to wrong answers because the router’s decision is based on administrative distance when prefix lengths are equal. Ignoring administrative distance causes confusion about why traffic prefers one route over another in multi-protocol environments.
Technical deep dive
How to think about this question
Administrative distance (AD) is a key concept in Cisco routing that determines which routing protocol's route is preferred when multiple protocols provide routes to the same destination prefix. Each routing protocol has a default AD value, which is a measure of trustworthiness; lower AD values are preferred. EIGRP has a default AD of 90 for internal routes, while OSPF has a default AD of 110. When two routes have the same prefix length, the router uses AD to select the best route. In this scenario, both EIGRP and OSPF advertise the same /24 prefix to 10.10.10.200. Because the prefix lengths are identical, the router cannot use longest-prefix match to differentiate. Instead, it compares the administrative distances of the two routes. Since EIGRP’s AD (90) is lower than OSPF’s (110), the router installs the EIGRP route into the routing table and forwards traffic accordingly. A common exam trap is to assume that OSPF routes are always preferred over EIGRP or that routing protocol preference depends on the protocol itself rather than administrative distance. In practice, the router always uses AD to break ties between equal-length prefixes. Understanding this behavior is critical for CCNA candidates to correctly predict routing decisions and troubleshoot routing issues in multi-protocol environments.
KKey Concepts to Remember
- Administrative distance determines the trustworthiness of routing protocols and influences route selection when multiple protocols advertise the same prefix.
- EIGRP has a default administrative distance of 90 for internal routes, which is lower than OSPF’s default administrative distance of 110.
- When two routes have the same prefix length, the router prefers the route with the lower administrative distance to install in the routing table.
- Longest-prefix match is the primary factor in route selection, but when prefix lengths are equal, administrative distance becomes the deciding factor.
- OSPF and EIGRP can both advertise IPv4 routes, and the router can have routes from both protocols simultaneously in the routing table.
- Routing protocols do not inherently prefer smaller or larger subnet masks; route preference depends on prefix length and administrative distance.
- The router installs only one best route per destination prefix in the routing table, chosen based on prefix length and administrative distance.
- Understanding administrative distance helps avoid common mistakes in predicting routing behavior in multi-protocol 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.
Related practice questions
Related 200-301 practice-question pages
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
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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?
Administrative distance determines the trustworthiness of routing protocols and influences route selection when multiple protocols advertise the same prefix.
What is the correct answer to this question?
The correct answer is: Because EIGRP has a lower administrative distance than OSPF for the same prefix length. — Traffic uses the EIGRP route because the prefixes are the same length and EIGRP has the lower administrative distance by default. In practical terms, longest-prefix match does not separate the two candidates because both describe the same destination size. Once the prefix length is tied, the router prefers the route source it trusts more. EIGRP wins over OSPF in that comparison. This is a classic route-source preference question and a very important CCNA concept.
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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