350-501 Security and Services Practice Question
A service provider wants to prevent IP spoofing attacks from customer edge devices connected to a PE router. The customer prefixes are known and asymmetric routing is not present. Which uRPF mode should be configured on the PE-CE interface?
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
✓
Strict mode uRPF
Strict mode uRPF checks that the source IP address is reachable via the same interface the packet arrived on, and that the route points back to that interface. This is suitable when symmetric routing is guaranteed, as on PE-CE links in L3VPN.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
No uRPF needed because BGP prefix filtering prevents spoofing
Why it's wrong here
BGP prefix filtering prevents route hijacking but does not prevent spoofing of source IPs.
- ✓
Strict mode uRPF
Why this is correct
Strict mode verifies the source IP is reachable via the incoming interface, ideal for PE-CE links with symmetric routing.
- ✗
VRF-aware uRPF
Why it's wrong here
VRF-aware uRPF is not a mode; uRPF is VRF-aware automatically.
- ✗
Loose mode uRPF
Why it's wrong here
Loose mode only requires a route to the source IP, regardless of interface; used when asymmetric routing exists.
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 350-501 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 350-501 exam.