hardMultiple Choice
300-410 Practice Question: Is troubleshooting a VRF-Lite setup where two…
A network engineer is troubleshooting a VRF-Lite setup where two routers are connected via a serial link. Each router has VRF_SALES configured. The engineer configures EIGRP in VRF_SALES. The 'show ip eigrp vrf VRF_SALES neighbors' shows no neighbors. The 'show ip eigrp vrf VRF_SALES interfaces' shows the serial interface is passive. What is the most likely cause?
⚠ Common exam trap
The trap is focusing on AS number or network statement mismatches while ignoring the explicit 'passive' flag in the interface output, which is the direct cause of missing EIGRP neighbors.
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 'passive-interface default' command is configured under the EIGRP process for VRF_SALES.
If 'show ip eigrp vrf VRF_SALES interfaces' shows the serial interface as passive, EIGRP will not send or receive hello packets on it, so no neighbor adjacency can form. The 'passive-interface default' command under the EIGRP VRF process makes all interfaces passive by default, requiring explicit 'no passive-interface' for interfaces that should form adjacencies. This directly explains the passive state and missing neighbors.
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 'passive-interface default' command is configured under the EIGRP process for VRF_SALES.
Why this is correct
The serial interface is passive because EIGRP inherits the global `passive-interface default` setting unless overridden per interface. Under address-family configuration for VRF_SALES, the interface must be explicitly activated with `no passive-interface Serial x/y`, otherwise no hellos are sent and no neighbours form.
- ✗
The 'network' command for the serial interface's subnet is missing.
Why it's wrong here
A missing network statement prevents EIGRP from advertising the subnet, but the interface would still form neighbours; passivity specifically means no EIGRP packets are sent or received on the serial link. The network command is used when the interface is active but routes are absent.
- ✗
The 'autonomous-system' number is different on the two routers.
Why it's wrong here
Differing autonomous-system numbers prevent EIGRP adjacencies forming, but the passive interface shown in the output already blocks hellos on the serial link, so no neighbour can appear regardless. It is tempting because AS mismatch is a classic EIGRP adjacency fault, and would be correct if the interface were not passive.
- ✗
The 'metric weights' command is misconfigured.
Why it's wrong here
Metric weights alter EIGRP's composite metric calculation, which affects route selection, not whether an interface forms adjacencies. It is tempting because metric tuning is a genuine EIGRP troubleshooting step, and would be correct when neighbours are up but paths are chosen unexpectedly.
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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Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Cisco exam blueprint
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.