Question 1mediummultiple choice
Full question →mediummultiple choiceObjective-mapped
A router learns the same prefix from both OSPF and EIGRP. Which route is installed by default?
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 route because OSPF is link-state
Protocol type alone does not determine preference.
B
Best answer
The EIGRP route because it has the lower administrative distance
Correct. Lower AD wins between different routing protocols.
C
Distractor review
The route with the lower metric value regardless of protocol
Metrics are not directly compared across different protocols.
D
Distractor review
Both routes are always installed
Both routes are not automatically installed just because the prefix matches.
Common exam trap
Common exam trap: answer the scenario, not the keyword
A common exam trap is assuming that the routing protocol type or metric alone determines which route is installed when the same prefix is learned from multiple protocols. Many candidates mistakenly believe that OSPF, being a link-state protocol, always takes precedence over EIGRP or that the route with the lower metric is preferred regardless of protocol. This is incorrect because administrative distance is the primary factor in route selection across different protocols. Ignoring AD leads to the wrong answer choice and misunderstanding of Cisco routing behavior.
Technical deep dive
How to think about this question
Administrative distance (AD) is a fundamental concept in Cisco routing that determines the trustworthiness of routing information received from different sources. When a router learns the same IP prefix from multiple routing protocols, it does not compare their metrics directly because each protocol uses different metrics and scales. Instead, it compares the administrative distance values assigned to each protocol. The route with the lowest AD is preferred and installed in the routing table. EIGRP, a Cisco proprietary routing protocol, assigns an administrative distance of 90 to its internal routes. OSPF, a widely used link-state protocol, assigns an AD of 110. Because 90 is lower than 110, the router prefers the EIGRP route over the OSPF route when both advertise the same prefix. This behavior ensures consistent and predictable route selection in networks running multiple routing protocols. Metrics such as OSPF cost or EIGRP composite metric are used only to select the best route among multiple routes learned from the same protocol. For example, OSPF compares cost values to choose the best path within OSPF routes. However, when comparing routes from different protocols, these metrics are irrelevant. Administrative distance acts as a universal ranking system to resolve conflicts between protocols. In practical network design, understanding administrative distance is crucial when redistributing routes between protocols or running multiple routing protocols simultaneously. Network engineers must know that even if OSPF provides a better metric path, the router will still prefer EIGRP routes by default due to AD values. This knowledge helps avoid routing loops, suboptimal routing, and troubleshooting confusion in multi-protocol environments.
KKey Concepts to Remember
- When a router learns the same IP prefix from multiple routing protocols, it uses administrative distance (AD) to select the best route.
- EIGRP internal routes have a default administrative distance of 90, which is lower than OSPF's default AD of 110.
- Administrative distance is a Cisco-proprietary value that ranks the trustworthiness of routing information from different sources.
- Routing metrics such as cost or bandwidth are only compared between routes within the same routing protocol, not across different protocols.
- If two routes have the same prefix but come from different protocols, the route with the lowest AD is installed in the routing table.
- OSPF is a link-state routing protocol, and EIGRP is an advanced distance-vector protocol, but protocol type alone does not determine route preference.
- Routers do not install multiple routes for the same prefix from different protocols by default; only the best route based on AD is installed.
- Understanding administrative distance helps network engineers predict route selection behavior in multi-protocol environments.
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 has routes for 10.10.0.0/16, 10.10.20.0/24, and a default route. Which route is used for destination 10.10.20.55?
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
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 4
What is the OSPF metric called?
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?
When a router learns the same IP prefix from multiple routing protocols, it uses administrative distance (AD) to select the best route.
What is the correct answer to this question?
The correct answer is: The EIGRP route because it has the lower administrative distance — When identical prefixes are learned from different routing protocols, the router compares administrative distance first. EIGRP internal routes use AD 90, while OSPF uses AD 110.
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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