Question 61 of 1,840
mediumMultiple ChoiceObjective-mapped
350-401 Practice Question: An engineer is configuring a FlexVPN…
An engineer is configuring a FlexVPN hub-and-spoke network. The hub router has a loopback0 with IP 10.0.0.1/32. The spokes are configured to use IKEv2 with certificates. The engineer notices that the spokes can establish the IKEv2 tunnel and can ping the hub's tunnel IP, but cannot reach the loopback0 address. The hub has a static route for the spoke subnets. What is the most likely issue?
⚠ Common exam trap
Cisco often tests the distinction between tunnel reachability (IKEv2 and tunnel interface up) and routing reachability (prefixes advertised over the tunnel), leading candidates to incorrectly focus on IKEv2 or certificate issues when the tunnel is already established.
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 loopback0 is not advertised in the routing protocol.
The spokes can establish the IKEv2 tunnel and ping the hub's tunnel IP, confirming that the tunnel interface is up and the IKEv2 session is functional. However, the loopback0 address (10.0.0.1/32) is not reachable from the spokes because it is not advertised into the routing protocol (e.g., OSPF, EIGRP, or BGP) used over the FlexVPN tunnel. Without a route to the loopback0 prefix, the spokes' traffic to 10.0.0.1 is dropped by the hub's routing table, even though the tunnel is operational.
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 IKEv2 proposal does not match between hub and spoke.
Why it's wrong here
The tunnel is established, so IKEv2 is working.
- ✗
The certificate authority is not trusted by the hub.
Why it's wrong here
Certificate trust issues would prevent tunnel establishment.
- ✗
The tunnel interface is not in an up/up state.
Why it's wrong here
The tunnel is up because the spokes can ping the tunnel IP.
- ✓
The loopback0 is not advertised in the routing protocol.
Why this is correct
Correct because without a route, the spokes cannot reach the loopback.
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.
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Last reviewed: Jul 4, 2026
This 350-401 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 350-401 exam.
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