hardMultiple ChoiceObjective-mapped
300-410 Practice Question: An engineer configures unicast Reverse Path…
An engineer configures unicast Reverse Path Forwarding (uRPF) in strict mode on an interface facing the Internet. Legitimate traffic from a customer network is being dropped. The traffic has a source IP that belongs to the customer's prefix, which is reachable via a different interface on the router. Which 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 customer traffic is arriving on an interface where the return path to the source is via a different interface, violating strict uRPF.
Strict uRPF checks that the source IP of incoming packets has a route back out the same interface. If the best path to the source IP is via a different interface (asymmetric routing), the packet is dropped. This is a classic edge case with strict uRPF in asymmetric routing scenarios.
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 'ip verify unicast source reachable-via any' command was used instead of 'rx'.
Why it's wrong here
That would be loose mode, which would not drop the traffic.
- ✗
The router has a default route pointing out the same interface, causing uRPF to pass all traffic.
Why it's wrong here
Default route can cause uRPF to pass traffic that should be dropped.
- ✓
The customer traffic is arriving on an interface where the return path to the source is via a different interface, violating strict uRPF.
Why this is correct
Strict uRPF requires symmetric routing; asymmetric routing causes drops.
- ✗
The 'ip urpf allow-default' command is missing, causing default routes to be ignored.
Why it's wrong here
Allow-default affects loose mode, not strict mode.
Quick reference
Asymmetric Encryption Algorithm Comparison
| Algorithm | Key Exchange | Signatures | Equivalent Security Key | Notes |
|---|---|---|---|---|
| RSA-3072 | Yes | Yes | 128-bit | Widely deployed; slow for bulk data |
| ECDSA P-256 | No | Yes | 128-bit | Fast signatures; standard TLS certs |
| ECDH / ECDHE | Yes | No | 128-bit | Perfect forward secrecy in TLS 1.3 |
| DH / DHE | Yes | No | 128-bit (3072-bit key) | Replaced by ECDHE in modern TLS |
| Ed25519 | No | Yes | ~128-bit | SSH keys, modern PKI |
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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.