The answer is the interface cost used as a tie-breaker for OSPF E2 routes. While OSPF E2 routes by design ignore the internal path cost to the ASBR and only advertise the external metric, Cisco IOS applies a tie-breaking rule when two E2 routes share the same external metric: it compares the cost of the outgoing interface. The route with the lower interface cost is preferred, which is why in this scenario all traffic to 10.1.1.0/24 flows through the 10.0.1.2 next hop, assuming that interface has a lower cost than the one toward 10.0.2.2. On the ENCOR 350-401 exam, this concept tests your understanding of OSPF path selection nuances, often appearing as a trick where students assume E2 routes never factor internal costs. A common trap is forgetting that tie-breaking still occurs at the forwarding decision level. Memory tip: think “E2 ignores the journey, but the router still checks the doorstep cost.”
350-401 Infrastructure Practice Question
This 350-401 practice question tests your understanding of infrastructure. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. 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
Refer to the exhibit.
R1# show ip route | include 10.1.1.0
O E2 10.1.1.0/24 [110/20] via 10.0.1.2, 00:00:34, GigabitEthernet0/0
O E2 10.1.1.0/24 [110/20] via 10.0.2.2, 00:00:34, GigabitEthernet0/1
R1# show ip ospf interface GigabitEthernet0/0 | include Cost
Process ID 1, Router ID 1.1.1.1, Network Type BROADCAST, Cost: 10
R1# show ip ospf interface GigabitEthernet0/1 | include Cost
Process ID 1, Router ID 1.1.1.1, Network Type BROADCAST, Cost: 100
R1# traceroute 10.1.1.1 source Loopback0
Type escape sequence to abort.
Tracing the route to 10.1.1.1
1 10.0.1.2 4 msec 4 msec 4 msec
2 10.0.3.2 8 msec 8 msec 8 msec
Refer to the exhibit. R1 has two equal-cost OSPF E2 routes to 10.1.1.0/24 via two different next hops. However, when tracing to 10.1.1.1, all traffic uses the path through 10.0.1.2. What is the most likely reason?
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.
Refer to the exhibit.
R1# show ip route | include 10.1.1.0
O E2 10.1.1.0/24 [110/20] via 10.0.1.2, 00:00:34, GigabitEthernet0/0
O E2 10.1.1.0/24 [110/20] via 10.0.2.2, 00:00:34, GigabitEthernet0/1
R1# show ip ospf interface GigabitEthernet0/0 | include Cost
Process ID 1, Router ID 1.1.1.1, Network Type BROADCAST, Cost: 10
R1# show ip ospf interface GigabitEthernet0/1 | include Cost
Process ID 1, Router ID 1.1.1.1, Network Type BROADCAST, Cost: 100
R1# traceroute 10.1.1.1 source Loopback0
Type escape sequence to abort.
Tracing the route to 10.1.1.1
1 10.0.1.2 4 msec 4 msec 4 msec
2 10.0.3.2 8 msec 8 msec 8 msec
A
One route has a higher administrative distance.
Why wrong: Incorrect: Both routes have AD 110.
B
A default route is overriding the specific route.
Why wrong: Incorrect: No default route is shown.
C
The route via 10.0.2.2 is an E1 route.
Why wrong: Incorrect: Both are E2 as shown.
D
OSPF E2 routes do not factor interface cost; but the router uses the interface cost as a tie-breaker for equal-cost routes.
Correct: When E2 metrics are equal, some implementations prefer the path with lower interface cost.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
OSPF E2 routes do not factor interface cost; but the router uses the interface cost as a tie-breaker for equal-cost routes.
OSPF E2 routes do not include the internal cost to the ASBR; the cost shown in the routing table is the external metric only. When two E2 routes have the same external metric, Cisco IOS uses the interface cost as a tie-breaker to select the best next hop. In this scenario, the interface to 10.0.1.2 has a lower cost than the interface to 10.0.2.2, so all traffic is forwarded via 10.0.1.2.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
OSPF E2 routes do not factor interface cost; but the router uses the interface cost as a tie-breaker for equal-cost routes.
Why this is correct
Correct: When E2 metrics are equal, some implementations prefer the path with lower interface cost.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the subtle tie-breaking behavior for OSPF E2 routes, where candidates mistakenly assume that equal-cost E2 routes will always be load-balanced, ignoring the interface cost tie-breaker that Cisco IOS applies.
Trap categories for this question
Command / output trap
Incorrect: No default route is shown.
Detailed technical explanation
How to think about this question
Under the hood, when OSPF installs multiple E2 routes with the same external metric into the routing table, the CEF (Cisco Express Forwarding) load-balancing decision uses the next-hop interface cost as a secondary tie-breaker. This behavior is documented in Cisco's OSPF design guide and can be verified with 'show ip route 10.1.1.0' where only one next hop appears despite equal metrics. In real-world scenarios, this can cause unexpected traffic patterns when redesigning OSPF areas or adding redundant links.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
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
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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 350-401 question in full detail.
Infrastructure — This question tests Infrastructure — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: OSPF E2 routes do not factor interface cost; but the router uses the interface cost as a tie-breaker for equal-cost routes. — OSPF E2 routes do not include the internal cost to the ASBR; the cost shown in the routing table is the external metric only. When two E2 routes have the same external metric, Cisco IOS uses the interface cost as a tie-breaker to select the best next hop. In this scenario, the interface to 10.0.1.2 has a lower cost than the interface to 10.0.2.2, so all traffic is forwarded via 10.0.1.2.
What should I do if I get this 350-401 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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?
Read the scenario before looking for a memorised answer.
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