300-410 Infrastructure Security Practice Question
A network engineer is configuring Unicast Reverse Path Forwarding (uRPF) on a Cisco IOS router to mitigate spoofed source IP addresses. The engineer wants to ensure that uRPF is applied in a way that allows asymmetric routing. Which uRPF mode should be configured?
⚠ Common exam trap
The trap here is assuming that strict mode uRPF can be used with asymmetric routing; strict mode requires the reverse path to match the incoming interface, which fails in asymmetric setups.
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
✓
Loose mode
Loose mode uRPF verifies that the source IP address is present in the routing table, but does not require the packet to arrive on the same interface as the route to the source. This allows asymmetric routing while still providing anti-spoofing protection. Strict mode would drop packets in asymmetric environments. VLAN mode and feasible path mode are not standard uRPF modes that allow asymmetric routing.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
VLAN mode
Why it's wrong here
VLAN mode is not a valid uRPF mode on Cisco IOS. uRPF modes are strict, loose, and possibly 'allow-default' or 'allow-self-ping' as options. VLAN mode is not a recognized configuration for uRPF. Therefore, this is incorrect.
- ✗
Feasible path mode
Why it's wrong here
Feasible path uRPF is a variation that uses the feasible path from the routing table to verify the source. It is not a standard mode and does not specifically allow asymmetric routing. It is more restrictive than loose mode. The requirement is to allow asymmetric routing, which is best met by loose mode.
- ✗
Strict mode
Why it's wrong here
Strict mode uRPF requires that the source IP address of an incoming packet be reachable via the same interface that the packet arrived on. This does not allow asymmetric routing, where the return path may be different. Strict mode would drop packets in asymmetric scenarios, so it is not suitable.
- ✓
Loose mode
Why this is correct
Loose mode uRPF checks that the source IP address is reachable via any interface in the routing table, not necessarily the incoming interface. This allows asymmetric routing because the return path can be different. It still provides spoofing mitigation by verifying the source is routable. This meets the requirement.
Visual reference
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 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.