hardMultiple ChoiceObjective-mapped
300-410 Practice Question: Router R1 and R2 are running EIGRP as the IGP,…
Router R1 and R2 are running EIGRP as the IGP, and R1 is redistributing a connected subnet 10.1.1.0/24 into EIGRP. R2 also runs BGP with an external peer, and BGP is redistributing the same prefix 10.1.1.0/24 into EIGRP with a route-map that sets the administrative distance to 100. On R3, a downstream EIGRP router, 'show ip route 10.1.1.0' shows the route via R2. What is the most likely cause of suboptimal routing?
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
✓
The internal EIGRP route is not present in R3's routing table due to a distribute-list inbound from R1, so the redistributed route with AD 100 is the only path.
EIGRP internal routes have AD 90, external routes AD 170. Redistribution from BGP into EIGRP creates external routes (AD 170) unless a route-map changes the distance. Setting AD to 100 makes the redistributed route preferred over the original internal route (AD 90) because 100 > 90, so the internal route should be preferred. However, if the internal route is not present due to a filter, or if the distance is set lower than 90, the redistributed route is chosen. The correct answer is that the route-map set distance 100 is higher than 90, so the internal route (AD 90) is still preferred; the issue is that the internal route is being suppressed by a distribute-list on R3.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The route-map set distance 100 overrides the default AD, making the redistributed route preferred over the internal route (AD 90).
Why it's wrong here
100 is higher than 90, so internal route is still preferred.
- ✓
The internal EIGRP route is not present in R3's routing table due to a distribute-list inbound from R1, so the redistributed route with AD 100 is the only path.
Why this is correct
If the internal route is filtered, the redistributed route becomes the best path, causing suboptimal routing.
- ✗
The redistributed route has AD 170 by default, and the route-map is ignored because redistribution from BGP always uses AD 170.
Why it's wrong here
Route-map can change AD.
- ✗
R3 prefers routes with lower metric, not AD, and the redistributed route has a better metric.
Why it's wrong here
AD is checked first; if AD is equal, metric is compared.
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
Related to this question
About these practice questions
Courseiva writes every 300-410 question from scratch — 1,966 in total, each with an explanation and a wrong-answer breakdown. None are copied from real exams or dumps. Learn why practice questions differ from exam dumps →
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 300-410 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 300-410 exam.