LPIC-2 Advanced Networking Configuration Practice Question
A company wants to set up a Linux bridge to connect a wireless interface (wlan0) to a wired interface (eth0) to allow devices on the wired network to access the internet through the wireless uplink. The Linux server runs Debian with hostapd to create an access point on wlan0. The administrator creates a bridge br0 using brctl and adds eth0 and wlan0 as ports. They assign IP 192.168.10.1/24 to br0 and start hostapd. Clients on the wired network can access the internet, but cannot ping clients on the wireless network, and vice versa. The administrator verifies that both interfaces are enslaved to br0 (brctl show shows both). They also confirm that IP forwarding is enabled and there are no iptables rules blocking anything. Which of the following is the most likely cause?
⚠ Common exam trap
Many exam-takers assume bridging works identically on wireless and wired interfaces, overlooking the 802.11 frame format limitation that requires 4-address mode for transparent bridging.
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
✓
The wireless interface wlan0 is not set to 4-address mode (WDS) to allow bridging.
A is correct because a standard wireless interface (station mode) uses 3-address frames (source, destination, BSSID) and drops frames with a fourth address, which is required for bridging. When a bridge forwards a frame from the wired side to the wireless side, it uses the MAC addresses of the original source and destination, but the wireless medium requires the fourth address (the transmitter address) to identify the bridge itself. Without enabling 4-address mode (WDS) on wlan0, the wireless driver will reject these bridged frames, preventing communication between wired and wireless clients.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
The wireless interface wlan0 is not set to 4-address mode (WDS) to allow bridging.
Why this is correct
Bridging requires 4-address frames on wireless interfaces.
- ✗
The DHCP server is only listening on the bridge interface, not on the individual interfaces.
Why it's wrong here
DHCP server listening on br0 is sufficient since both networks are bridged.
- ✗
The hostapd configuration is missing the 'bridge' parameter to bind to the bridge.
Why it's wrong here
hostapd's bridge parameter is for adding the AP interface, but wlan0 is already in bridge.
- ✗
The iptables firewall is blocking broadcast traffic between bridge ports.
Why it's wrong here
No iptables rules are present.
Quick reference
Access Control Model Comparison
| Model | Acronym | Who Controls Access? | Best For |
|---|---|---|---|
| Discretionary Access Control | DAC | Resource owner | Small teams, file shares |
| Mandatory Access Control | MAC | System / security labels | Classified govt / military |
| Role-Based Access Control | RBAC | Administrator (via roles) | Enterprise environments |
| Attribute-Based Access Control | ABAC | Policy engine (user + resource attributes) | Fine-grained, dynamic policies |
| Rule-Based Access Control | RuBAC | System rules / ACLs | Firewall rules, network ACLs |
Go deeper
Related to this question
About these practice questions
Courseiva writes every LPIC-2 question from scratch — 507 in total, each with an explanation and a wrong-answer breakdown. None are copied from real exams or dumps. Learn why practice questions differ from exam dumps →
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.