The answer is that the router installs both routes and uses equal-cost multipath forwarding. This is correct because OSPF’s metric logic treats paths with identical cost as equally valid, so the router does not discard one; instead, it leverages OSPF equal cost multipath ECMP to load-balance traffic across both links, improving resilience and bandwidth utilization. On the CCNA 200-301 v2 exam, this question tests your understanding that routing protocols do not always force a single best path—a common trap is assuming the router must pick one winner. Remember the memory tip: “Equal cost means equal opportunity—both paths get a job.”
CCNA IP Routing Practice Question
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: oSPF selects routes based on the lowest cumulative cost metric calculated from interface bandwidth values along the path.. 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.
An OSPF-enabled router has two paths to the same destination network, and both paths have the same OSPF cost. What is the most likely default behavior?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Install both routes and use equal-cost multipath forwarding
When OSPF learns two equally good paths to the same destination, the router can install both and perform equal-cost multipath forwarding. In plain language, the router does not have to throw one away simply because there are two valid answers. If the routes are truly equal from OSPF’s perspective, it can use both paths to improve resilience and share traffic.
This is a classic routing behavior question because many candidates assume the router must always choose only one best path. In reality, equal-cost multipath is a normal feature in many routing environments. The key is that the paths must be equally good according to the protocol’s metric logic.
Key principle: OSPF selects routes based on the lowest cumulative cost metric calculated from interface bandwidth values along the path.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Install both routes and use equal-cost multipath forwarding
Why this is correct
This is correct because OSPF can install multiple equal-cost paths to the same destination.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
OSPF selects routes based on the lowest cumulative cost metric calculated from interface bandwidth values along the path.
✗
Discard both routes because OSPF cannot handle duplicates
Why it's wrong here
This is wrong because OSPF can use multiple equal-cost routes.
When this WOULD be correct
In a hypothetical exam scenario where the question specifies that OSPF is configured to only allow unique routes and duplicates are filtered out, option B would be correct. For example, if the question states that 'OSPF is configured with a unique route filter,' then discarding duplicates would be the expected behavior.
✗
Always keep only the route learned first
Why it's wrong here
This is wrong because equal-cost multipath behavior is possible and common.
When this WOULD be correct
In a different scenario where a routing protocol only allows a single route to a destination, such as a legacy protocol that does not support multipath routing, the question might ask what happens when two routes are learned, leading to the correct answer being to keep only the first learned route.
✗
Replace both routes with a default route
Why it's wrong here
This is wrong because there is no need to prefer a default route over valid equal-cost specific routes.
When this WOULD be correct
In a different scenario, if the question specified that OSPF was configured to use a default route for all traffic due to specific routing policies or if the network was designed to only allow a default route for redundancy, then this option could be correct.
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.
✓Install both routes and use equal-cost multipath forwardingCorrect answer▾
Why this is correct
This is correct because OSPF can install multiple equal-cost paths to the same destination.
✗Discard both routes because OSPF cannot handle duplicatesWrong answer — click to see why▾
Why this is wrong here
This option is incorrect because OSPF can handle multiple equal-cost paths and does not discard routes simply due to duplication. Instead, it installs both routes for load balancing.
★ When this WOULD be the correct answer
In a hypothetical exam scenario where the question specifies that OSPF is configured to only allow unique routes and duplicates are filtered out, option B would be correct. For example, if the question states that 'OSPF is configured with a unique route filter,' then discarding duplicates would be the expected behavior.
Why candidates choose this
Candidates might choose this option due to a misunderstanding of OSPF's capabilities, thinking that it cannot manage multiple paths to the same destination, leading to the assumption that duplicates must be discarded.
✗Always keep only the route learned firstWrong answer — click to see why▾
Why this is wrong here
This option is incorrect because OSPF is designed to support equal-cost multipath routing; it does not discard routes simply because they were learned at different times. Both routes would be installed in the routing table if they have the same cost.
★ When this WOULD be the correct answer
In a different scenario where a routing protocol only allows a single route to a destination, such as a legacy protocol that does not support multipath routing, the question might ask what happens when two routes are learned, leading to the correct answer being to keep only the first learned route.
Why candidates choose this
Candidates may find this option tempting due to a misunderstanding of OSPF's capabilities, mistakenly believing that it cannot handle multiple routes to the same destination, leading them to choose the option that suggests discarding duplicates.
✗Replace both routes with a default routeWrong answer — click to see why▾
Why this is wrong here
This option is incorrect because OSPF does not replace multiple equal-cost routes with a default route; it can use multiple paths for load balancing instead. The default behavior in OSPF is to install all equal-cost routes in the routing table.
★ When this WOULD be the correct answer
In a different scenario, if the question specified that OSPF was configured to use a default route for all traffic due to specific routing policies or if the network was designed to only allow a default route for redundancy, then this option could be correct.
Why candidates choose this
Candidates might choose this option due to a misunderstanding of OSPF's behavior with multiple routes, confusing it with other routing protocols that may discard routes in favor of a default route under certain conditions.
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
A frequent exam trap is believing that OSPF must select only one best route when multiple paths have the same cost. Many candidates mistakenly think OSPF discards duplicates or keeps only the first learned route. This misunderstanding leads to incorrect answers suggesting route discarding or default route replacement. The trap arises because some routing protocols or older implementations do not support equal-cost multipath. However, OSPF explicitly supports installing multiple equal-cost routes to improve load balancing and fault tolerance, so assuming otherwise causes errors in exam scenarios.
Detailed technical explanation
How to think about this question
OSPF (Open Shortest Path First) is a link-state routing protocol that calculates the best path to a destination based on the cumulative cost metric, which is derived from the bandwidth of each link along the route. The cost is inversely proportional to bandwidth, meaning higher bandwidth links have lower cost values. When a router receives multiple OSPF routes to the same destination, it compares the total cost of each path to determine the best route.
If OSPF finds two or more paths with exactly the same cost, it installs all these equal-cost routes into the routing table. This behavior is known as equal-cost multipath (ECMP) forwarding. ECMP allows the router to forward packets over multiple paths simultaneously, effectively balancing the traffic load and providing redundancy. Cisco routers typically support up to four or more ECMP routes by default, depending on the platform and configuration.
A common exam trap is assuming that OSPF will only keep one route and discard the others when multiple equal-cost paths exist. In reality, OSPF’s design encourages using all equal-cost paths to optimize network utilization and resilience. This behavior contrasts with protocols or scenarios where only a single best route is chosen. Understanding ECMP is critical for CCNA candidates because it affects how traffic is distributed and how routing tables are populated in OSPF-enabled networks.
KKey Concepts to Remember
OSPF selects routes based on the lowest cumulative cost metric calculated from interface bandwidth values along the path.
When OSPF discovers multiple paths with the same cost to a destination, it installs all equal-cost routes into the routing table for load balancing.
Equal-cost multipath (ECMP) forwarding allows OSPF routers to distribute traffic evenly across multiple paths with identical metrics to improve bandwidth utilization and redundancy.
OSPF does not discard routes simply because duplicates exist; it prefers to use all equal-cost routes rather than choosing only one.
The OSPF routing process compares path costs and installs multiple routes only if their costs are exactly equal according to OSPF’s metric calculation.
OSPF’s ability to install multiple equal-cost routes contrasts with some protocols that only select a single best path based on administrative distance or metric.
Routers performing ECMP use per-packet or per-flow load balancing methods to forward traffic across equal-cost paths without causing routing loops.
OSPF’s metric is based on bandwidth, so paths with different bandwidths will have different costs, preventing ECMP unless costs match exactly.
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
OSPF selects routes based on the lowest cumulative cost metric calculated from interface bandwidth values along the path.
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 oSPF selects routes based on the lowest cumulative cost metric calculated from interface bandwidth values along the path., then practise related 200-301 questions on the same topic to reinforce the concept.
IP Routing — This question tests IP Routing — OSPF selects routes based on the lowest cumulative cost metric calculated from interface bandwidth values along the path..
What is the correct answer to this question?
The correct answer is: Install both routes and use equal-cost multipath forwarding — When OSPF learns two equally good paths to the same destination, the router can install both and perform equal-cost multipath forwarding. In plain language, the router does not have to throw one away simply because there are two valid answers. If the routes are truly equal from OSPF’s perspective, it can use both paths to improve resilience and share traffic.
This is a classic routing behavior question because many candidates assume the router must always choose only one best path. In reality, equal-cost multipath is a normal feature in many routing environments. The key is that the paths must be equally good according to the protocol’s metric logic.
What should I do if I get this 200-301 question wrong?
Review oSPF selects routes based on the lowest cumulative cost metric calculated from interface bandwidth values along the path., then practise related 200-301 questions on the same topic to reinforce the concept.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
OSPF selects routes based on the lowest cumulative cost metric calculated from interface bandwidth values along the path.
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