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300-410 Practice Question: A DMVPN network uses PBR to route traffic from…
A DMVPN network uses PBR to route traffic from spoke routers to specific hubs based on source IP. After a hub failure, traffic from spoke 1 (source 192.168.1.0/24) is being sent to a backup hub, but the backup hub drops the traffic. Router R1 (spoke) shows: 'show ip policy' shows PBR applied, 'debug ip policy' shows traffic being forwarded to next-hop 10.1.1.2 (backup hub). Router R2 (backup hub) shows: 'show ip route 192.168.1.0' returns no route. What is the root cause?
⚠ Common exam trap
300-410 often tests the misconception that fixing the spoke's PBR configuration will resolve the issue, when the real problem is the return path on the hub — candidates must check both directions of traffic flow.
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 backup hub does not have a route to the source subnet, causing it to drop traffic. Add a static route or enable routing protocol on the backup hub for the spoke subnet.
The backup hub (R2) has no route to the source subnet 192.168.1.0/24, as confirmed by 'show ip route 192.168.1.0' returning no route. Even though PBR on the spoke correctly forwards traffic to the backup hub, the backup hub cannot return traffic to the source subnet, so it drops the packets. Adding a static route or enabling a routing protocol on the backup hub for the spoke subnet resolves the issue.
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 backup hub does not have a route to the source subnet, causing it to drop traffic. Add a static route or enable routing protocol on the backup hub for the spoke subnet.
Why this is correct
PBR successfully forwards spoke traffic to the backup hub, but that hub has no route for 192.168.1.0/24, so it drops the packets. Adding a static route or enabling a routing protocol on the backup hub restores reachability to the source subnet.
- ✗
The PBR route-map on the spoke is missing a 'set ip next-hop verify-availability' command, causing it to use the backup hub even when it is not fully reachable.
Why it's wrong here
verify-availability only checks next-hop reachability before applying a set clause; the hub is reachable, yet drops traffic because it has no route to 192.168.1.0/24. This would be tempting if the next hop were down. The actual fault is the missing return route on R2.
- ✗
The spoke's routing table has a better route to the destination via the backup hub, overriding PBR.
Why it's wrong here
PBR takes precedence over the routing table for matched traffic, and debug ip policy confirms the next-hop 10.1.1.2 was used, so no competing route overrode it. This would be tempting if PBR were unapplied. The failure is the backup hub's missing return route.
- ✗
The backup hub has a route to the source subnet but with a higher administrative distance, causing it to be ignored.
Why it's wrong here
The output states no route exists at all, so administrative distance is irrelevant; AD only arbitrates between competing routes to the same prefix. This would be tempting if two routes existed and the wrong one won. The backup hub simply lacks any route back to 192.168.1.0/24.
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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JA
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.