CCNA Network Services and Security Practice Question
R1 learns three OSPF routes to different destinations:
O 10.10.10.0/24
O IA 10.20.20.0/24 O E2 10.30.30.0/24
Which statement is correct about these route types?
⚠ Common exam trap
A frequent exam trap is confusing the OSPF route codes, especially mistaking 'O IA' (inter-area) for an external route redistributed from another protocol. Candidates often incorrectly assume that 'O IA' means external, but it actually represents routes learned from a different OSPF area within the same autonomous system. Another common mistake is thinking the 'O' code indicates EIGRP routes, which it does not; EIGRP uses different codes such as 'D'. This confusion can cause candidates to select incorrect answers about route origins or types. Carefully distinguishing between intra-area, inter-area, and external routes based on OSPF codes is essential to avoid this pitfall.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
O E2 is an OSPF external type 2 route.
An O route is intra-area, O IA is interarea, and O E2 is an external type 2 route redistributed into OSPF. The codes describe route origin, not just preference. CCNA expects you to identify them quickly when reading the routing table.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
O IA is an external route redistributed from another routing protocol.
Why it's wrong here
The code 'O IA' in OSPF does not indicate an external route; it stands for an interarea route. Interarea routes are learned from a different OSPF area through an Area Border Router (ABR) using type 3 summary LSAs. External routes redistributed from other protocols are instead marked as 'O E1' or 'O E2', which correspond to type 5 external LSAs, not 'O IA'.
When this WOULD be correct
In a different scenario where the question specifies routes learned from a redistribution of another routing protocol into OSPF, such as EIGRP or BGP, option A would be correct if it referred to an external route. For example, 'Which OSPF route type indicates an external route redistributed from another protocol?'
- ✓
O E2 is an OSPF external type 2 route.
Why this is correct
In OSPF, the route code 'O' indicates a route learned via the OSPF protocol, and 'E2' specifically denotes an external type 2 route. This type is redistributed from another routing protocol into OSPF, and its metric is the external cost only, without adding the internal cost to the ASBR. The 'O E2' code is exactly the standard representation for such externally redistributed type 2 routes.
- ✗
O means the route was learned through EIGRP.
Why it's wrong here
'O' is the Cisco IOS route code for OSPF-learned routes, not EIGRP. EIGRP routes are indicated by 'D' for internal EIGRP and 'EX' for external EIGRP routes. Therefore, seeing 'O' in a routing table entry means the route was sourced from an OSPF neighbor, not from an EIGRP router, making this option incorrect.
When this WOULD be correct
In a different question, if the context specifies that the routing table is being analyzed for EIGRP routes, and the notation 'D' is used for EIGRP, then an option stating 'O' indicates EIGRP could be correct if misinterpreted. For example, if the question mistakenly labeled EIGRP routes with 'O', it could lead to this being the right answer.
- ✗
All three routes were learned from the same OSPF area type.
Why it's wrong here
The three route codes 'O', 'O IA', and 'O E2' denote different OSPF route types: intra-area, interarea, and external, respectively. Intra-area routes are learned via type 1 or 2 LSAs within the same area, interarea routes cross area boundaries via ABRs, and external routes originate from outside the OSPF domain. Because these represent fundamentally different origins, they cannot all come from the same OSPF area type.
When this WOULD be correct
In a different question setup where all routes were explicitly stated to be learned from the same OSPF area, such as 'All routes are from OSPF area 0,' this option would be correct as it would confirm that they share the same area type.
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.
✓O E2 is an OSPF external type 2 route.Correct answer▾
Why this is correct
In OSPF, the route code 'O' indicates a route learned via the OSPF protocol, and 'E2' specifically denotes an external type 2 route. This type is redistributed from another routing protocol into OSPF, and its metric is the external cost only, without adding the internal cost to the ASBR. The 'O E2' code is exactly the standard representation for such externally redistributed type 2 routes.
✗O IA is an external route redistributed from another routing protocol.Wrong answer — click to see why▾
Why this is wrong here
The option A is incorrect because 'O IA' indicates an inter-area route in OSPF, not an external route. External routes are denoted by 'O E1' or 'O E2'.
★ When this WOULD be the correct answer
In a different scenario where the question specifies routes learned from a redistribution of another routing protocol into OSPF, such as EIGRP or BGP, option A would be correct if it referred to an external route. For example, 'Which OSPF route type indicates an external route redistributed from another protocol?'
Why candidates choose this
Candidates may confuse OSPF route types due to similarities in terminology, leading them to mistakenly associate 'IA' with external routes, especially if they have experience with multiple routing protocols.
✗O means the route was learned through EIGRP.Wrong answer — click to see why▾
Why this is wrong here
This option is incorrect because 'O' indicates an OSPF route, not an EIGRP route. OSPF and EIGRP are distinct routing protocols, and OSPF routes are denoted with 'O' while EIGRP routes use 'D'.
★ When this WOULD be the correct answer
In a different question, if the context specifies that the routing table is being analyzed for EIGRP routes, and the notation 'D' is used for EIGRP, then an option stating 'O' indicates EIGRP could be correct if misinterpreted. For example, if the question mistakenly labeled EIGRP routes with 'O', it could lead to this being the right answer.
Why candidates choose this
Candidates may confuse the routing protocol identifiers due to similar acronyms and may mistakenly believe that 'O' could represent EIGRP in a context where multiple protocols are discussed, leading to misinterpretation.
✗All three routes were learned from the same OSPF area type.Wrong answer — click to see why▾
Why this is wrong here
This option is incorrect because the routes learned are from different OSPF types: O (intra-area), IA (inter-area), and E2 (external type 2), indicating they are not from the same OSPF area.
★ When this WOULD be the correct answer
In a different question setup where all routes were explicitly stated to be learned from the same OSPF area, such as 'All routes are from OSPF area 0,' this option would be correct as it would confirm that they share the same area type.
Why candidates choose this
Candidates might choose this option due to a misunderstanding of OSPF route types, mistakenly believing that all OSPF routes must originate from the same area, leading them to overlook the specific types presented.
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?”
Visual reference
Quick reference
Routing Protocol Comparison
| Protocol | Metric | Max Hops | Algorithm | Type |
|---|---|---|---|---|
| RIP v2 | Hop count | 15 | Bellman-Ford | Distance vector |
| OSPF | Cost (bandwidth) | Unlimited | Dijkstra (SPF) | Link state |
| EIGRP | Composite metric | Unlimited | DUAL | Hybrid |
| IS-IS | Cost | Unlimited | Dijkstra | Link state |
| BGP | Policy / attributes | Unlimited | Path vector | Path vector |
RIP's 15-hop limit makes it unsuitable for large networks. OSPF and EIGRP dominate modern enterprise deployments.
Go deeper
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 200-301 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 200-301 exam.