hardMultiple ChoiceObjective-mapped
300-410 Practice Question: Configures BFD for EIGRP on a point-to-point link
A network engineer configures BFD for EIGRP on a point-to-point link. The BFD session is up, but EIGRP neighbors are stuck in INIT state. The engineer checks that EIGRP hello packets are sent and received. Which of the following is the most likely explanation?
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 EIGRP K values are mismatched between the two routers, preventing the adjacency from forming.
EIGRP requires that the K values match between neighbors. If the K values are mismatched, EIGRP will not form an adjacency even if BFD is operational. This is a common misconfiguration because BFD does not enforce K value matching; it only reports link failures.
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 EIGRP K values are mismatched between the two routers, preventing the adjacency from forming.
Why this is correct
Correct. EIGRP requires matching K values to form an adjacency. BFD does not influence this check.
- ✗
The 'bfd all-interfaces' command is missing under the EIGRP process, so EIGRP ignores BFD state.
Why it's wrong here
Incorrect. The 'bfd all-interfaces' command enables BFD integration, but the issue here is that EIGRP is stuck in INIT, not that BFD is not used.
- ✗
The interface is configured with 'ip authentication mode eigrp' and 'ip authentication key-chain eigrp' with mismatched keys.
Why it's wrong here
Incorrect. Authentication issues would cause EIGRP hello packets to be dropped, not stuck in INIT; the neighbor would not appear at all.
- ✗
The EIGRP autonomous system number is different on each router.
Why it's wrong here
Incorrect. A mismatched AS number would prevent the neighbor from being discovered; the router would not even see the neighbor.
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.
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Variation 1. A network engineer is troubleshooting a scenario where two routers running EIGRP are not forming an adjacency. Both routers have BFD configured under the EIGRP process and on the interfaces. The BFD session is up and operational. However, the EIGRP neighbor status shows 'Pending' and never transitions to 'Up'. What is the most likely cause?
hard- A.The BFD timers are set too high, causing EIGRP to time out before BFD can respond.
- B.EIGRP is configured with 'no auto-summary' on one router and 'auto-summary' on the other.
- ✓ C.The EIGRP K-values are mismatched between the two routers.
- D.The interface is configured with 'bfd interval 50 min_rx 50 multiplier 3' but the neighbor expects different values.
Why C: EIGRP requires the BFD session to be fully established before it will bring up the adjacency. If the BFD session is up but EIGRP is stuck in Pending, the issue is often a mismatch in EIGRP K-values or authentication.
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.