350-501 Security and Services Practice Question
A service provider is deploying uRPF on customer-facing interfaces to prevent IP spoofing. The network has asymmetric routing due to multiple upstream connections. Which uRPF mode should be used?
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
Strict mode requires the source address to be reachable via the incoming interface, which fails with asymmetric routing. Loose mode only checks that the source address exists in the routing table, making it suitable for asymmetric paths.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Strict mode
Why it's wrong here
Strict mode will drop legitimate traffic with asymmetric routing.
- ✗
uRPF with allow-default
Why it's wrong here
allow-default is used for default routes, not for asymmetric routing.
- ✗
uRPF is not recommended for asymmetric routing
Why it's wrong here
Loose mode is specifically designed for asymmetric routing scenarios.
- ✓
Loose mode
Why this is correct
Loose mode allows asymmetric routing while still providing anti-spoofing.
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
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