This 200-301 practice question tests your understanding of ip routing. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. A key principle to apply: administrative distance determines the trustworthiness of routing protocols and influences route selection when multiple protocols advertise the same prefix.. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
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
Why is traffic to 10.10.10.200 using the EIGRP route instead of the OSPF route, given that both routes have the same prefix length?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Because EIGRP has a lower administrative distance than OSPF for the same prefix length.
When two routes have the same prefix length, the router uses administrative distance to choose the route with the lowest value. EIGRP has a default administrative distance of 90, while OSPF uses 110. Therefore, the EIGRP route is preferred.
Key principle: Administrative distance determines the trustworthiness of routing protocols and influences route selection when multiple protocols advertise the same prefix.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Because EIGRP has a lower administrative distance than OSPF for the same prefix length.
Administrative distance determines the trustworthiness of routing protocols and influences route selection when multiple protocols advertise the same prefix.
✗
Because OSPF routes are never installed when EIGRP is present.
Why it's wrong here
This is wrong because OSPF routes can still exist in the table even if they are not selected as best.
When this WOULD be correct
In a scenario where the question specifies that OSPF is configured to not participate in routing due to a specific configuration, such as a route map or filtering, this option could be correct. For example, if the question stated that OSPF was disabled or not operational, then EIGRP would be the only routing protocol providing routes.
✗
Because OSPF can be used only for IPv6 routes.
Why it's wrong here
This is wrong because OSPF is commonly used for IPv4 as well.
When this WOULD be correct
In a different scenario where the question specifies that only IPv6 routing protocols are being considered, and the traffic is directed to an IPv6 address, this option could be correct if the question implies that OSPF is not configured for IPv6 routes.
✗
Because EIGRP routes always have a smaller subnet mask than OSPF routes.
Why it's wrong here
This is wrong because route source does not determine the subnet mask length that way.
When this WOULD be correct
In a different scenario where the question specifies that EIGRP routes are always configured with a smaller subnet mask than OSPF routes, and the routing decision is based solely on the mask size, this option could be correct. For example, if the question asked why a specific route was preferred due to subnet mask comparison, then this option would apply.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.
✓Because EIGRP has a lower administrative distance than OSPF for the same prefix length.Correct answer▾
Why this is correct
This is correct because both routes are /24, so administrative distance becomes decisive and EIGRP wins.
✗Because OSPF routes are never installed when EIGRP is present.Wrong answer — click to see why▾
Why this is wrong here
This option is incorrect because OSPF can coexist with EIGRP on the same network, and routes from both protocols can be installed in the routing table based on their administrative distances.
★ When this WOULD be the correct answer
In a scenario where the question specifies that OSPF is configured to not participate in routing due to a specific configuration, such as a route map or filtering, this option could be correct. For example, if the question stated that OSPF was disabled or not operational, then EIGRP would be the only routing protocol providing routes.
Why candidates choose this
Candidates may choose this option due to a misunderstanding of how routing protocols interact, mistakenly believing that the presence of one protocol inherently prevents the installation of routes from another.
✗Because OSPF can be used only for IPv6 routes.Wrong answer — click to see why▾
Why this is wrong here
This option is incorrect because OSPF can be utilized for both IPv4 and IPv6 routes, making it irrelevant to the question about traffic routing to an IPv4 address (10.10.10.200).
★ When this WOULD be the correct answer
In a different scenario where the question specifies that only IPv6 routing protocols are being considered, and the traffic is directed to an IPv6 address, this option could be correct if the question implies that OSPF is not configured for IPv6 routes.
Why candidates choose this
Candidates may choose this option due to a misunderstanding of OSPF's capabilities, mistakenly believing that it is limited to IPv6, especially if they have encountered questions focused solely on IPv6 routing.
✗Because EIGRP routes always have a smaller subnet mask than OSPF routes.Wrong answer — click to see why▾
Why this is wrong here
This option is incorrect because EIGRP and OSPF can operate simultaneously with different subnet masks; the route selection is based on administrative distance, not subnet mask size.
★ When this WOULD be the correct answer
In a different scenario where the question specifies that EIGRP routes are always configured with a smaller subnet mask than OSPF routes, and the routing decision is based solely on the mask size, this option could be correct. For example, if the question asked why a specific route was preferred due to subnet mask comparison, then this option would apply.
Why candidates choose this
Candidates may choose this option due to a common misconception that EIGRP's efficiency is tied to its subnet mask size, leading them to overlook the fundamental routing decision factor of administrative distance.
Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Common exam traps
Common exam trap: answer the scenario, not the keyword
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.
Key takeaway
Administrative distance determines the trustworthiness of routing protocols and influences route selection when multiple protocols advertise the same prefix.
Real-world example
How this comes up in practice
A network engineer at a university connects two campus buildings via a fibre link. Both routers run OSPF, but no adjacency forms — even though both routers can ping each other. The engineer finds one router is in area 0 and the other in area 1. OSPF adjacency requires matching area numbers, hello/dead timers, and network type. IP reachability alone is not enough.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 200-301 question in full detail.
Review administrative distance determines the trustworthiness of routing protocols and influences route selection when multiple protocols advertise the same prefix., then practise related 200-301 questions on the same topic to reinforce the concept.
IP Routing — This question tests IP Routing — 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. — When two routes have the same prefix length, the router uses administrative distance to choose the route with the lowest value. EIGRP has a default administrative distance of 90, while OSPF uses 110. Therefore, the EIGRP route is preferred.
What should I do if I get this 200-301 question wrong?
Review administrative distance determines the trustworthiness of routing protocols and influences route selection when multiple protocols advertise the same prefix., then practise related 200-301 questions on the same topic to reinforce the concept.
What is the key concept behind this question?
Administrative distance determines the trustworthiness of routing protocols and influences route selection when multiple protocols advertise the same prefix.
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