LPIC-2 Advanced Networking Configuration Practice Question
A Linux router is experiencing asymmetric routing issues. The network has two internet connections (ISP1 and ISP2) with default routes. The administrator wants to ensure that traffic originating from a specific source IP uses ISP1 for both incoming and outgoing packets. Which ip rule configuration achieves this?
⚠ Common exam trap
The trap here is that candidates often forget to disable reverse path filtering (rp_filter) when implementing policy routing for asymmetric paths, assuming that adding the policy rule and custom table is sufficient, but the kernel's default strict rp_filter will silently drop return packets that arrive on a different 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
✓
ip rule add from 10.0.0.10 table isp1; ip route add default via 1.1.1.1 table isp1; sysctl -w net.ipv4.conf.all.rp_filter=0
It creates a policy routing rule that matches traffic from source IP 10.0.0.10 and directs it to a custom routing table named 'isp1', which contains a default route via ISP1's gateway (1.1.1.1). Additionally, disabling reverse path filtering (rp_filter=0) is essential to allow asymmetric routing — without it, the kernel would drop return packets arriving via a different interface than the one used for outgoing traffic, which is exactly the scenario in 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.
- ✗
ip rule add from 10.0.0.10 to 0/0 table isp1; ip route add default via 1.1.1.1 table isp1; ip rule add to 10.0.0.10 table isp1
Why it's wrong here
Extra rule for incoming traffic is unnecessary; rp_filter still may drop packets.
- ✓
ip rule add from 10.0.0.10 table isp1; ip route add default via 1.1.1.1 table isp1; sysctl -w net.ipv4.conf.all.rp_filter=0
Why this is correct
Policy routing with table-specific default and disabled rp_filter allows asymmetric routing.
- ✗
ip rule add from 10.0.0.10 table isp1; ip route add default via 1.1.1.1 table isp1
Why it's wrong here
Missing sysctl tuning; reverse path filtering will drop return packets arriving on a different interface.
- ✗
ip rule add from 10.0.0.10 table isp1; ip route add default via 1.1.1.1
Why it's wrong here
Default route not added to custom table; also no rp_filter adjustment.
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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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.