LFCS Networking Practice Question
Network Topology
Refer to the exhibit. A server has two interfaces: eth0 (public) and eth1 (internal). The firewall zone 'internal' is assigned to eth1. An administrator wants to allow TCP traffic on port 8080 from eth1 to the server. Which command will achieve this without affecting existing rules?
⚠ Common exam trap
Candidates often confuse `--permanent` with immediate effect, or incorrectly assume that `--add-service=http` is required for HTTP-based traffic on port 8080, when in fact `--add-port` directly specifies the port regardless of the service name.
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
✓
firewall-cmd --zone=internal --add-port=8080/tcp
It uses the `--zone=internal` flag to target the correct zone assigned to eth1, and `--add-port=8080/tcp` to open only TCP port 8080 without modifying any existing rules. The command is not `--permanent`, so it applies immediately to the runtime configuration, which is the default behavior when `--permanent` is omitted.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
firewall-cmd --permanent --zone=internal --add-port=8080/tcp
Why it's wrong here
This only adds the rule permanently; it does not apply it until a reload, so it's not immediate.
- ✗
firewall-cmd --zone=internal --add-service=http --add-port=8080/tcp
Why it's wrong here
Adding an unnecessary service (http) is not required and may affect existing rules.
- ✓
firewall-cmd --zone=internal --add-port=8080/tcp
Why this is correct
This adds the port to the internal zone temporarily but immediately, without reload.
- ✗
firewall-cmd --zone=public --add-port=8080/tcp
Why it's wrong here
This adds the port to the public zone, not the internal zone.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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