LPIC-2 Advanced Networking Configuration Practice Question
A Linux router is experiencing packet loss for connections that should be forwarded. The router's IP forwarding is enabled, and the routing table is correct. Which kernel parameter is most likely causing the issue?
⚠ Common exam trap
It's easy for candidates to assume packet loss must be due to IP forwarding being disabled or a routing table error, overlooking that Reverse Path Filtering can drop packets even when forwarding and routes are correct.
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
✓
net.ipv4.conf.all.rp_filter
The `net.ipv4.conf.all.rp_filter` parameter enables Reverse Path Filtering (RPF), which drops packets arriving on an interface if the kernel does not have a route back to the source IP via that same interface. On a router forwarding traffic between networks, strict RPF can cause packet loss when asymmetric routing is present, even though IP forwarding and the routing table are correct.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
net.ipv4.conf.all.rp_filter
Why this is correct
When set to 1 (strict) or 2 (loose), rp_filter can drop packets if the source IP is not reachable via the incoming interface, causing loss in complex routing scenarios.
- ✗
net.ipv4.conf.all.log_martians
Why it's wrong here
log_martians logs suspicious packets but does not drop them.
- ✗
net.ipv4.conf.all.accept_redirects
Why it's wrong here
Accepting redirects is unrelated to packet loss for forwarded traffic.
- ✗
net.ipv4.ip_forward
Why it's wrong here
ip_forward is already enabled as stated.
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 LPIC-2 practice question is part of Courseiva's free LPI 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 LPIC-2 exam.