How to Fix Intermittent Network Issues Caused by a Fax Machine?

N10-009 By islever Editorial Last updated Sep 1, 2026

Short answer

D Configure a VLAN.

Question

An office is experiencing intermittent connection issues. A network engineer identifies that the issue occurs whenever someone uses the fax machine that is connected to a switch. Which of the following should the engineer do first to resolve the issue?

Run a new Cat 5 line.
Enable 802.1Q tagging.
Change the MTU.
Configure a VLAN. Correct Answer

Key Takeaways

The question tests VLAN segmentation as a troubleshooting technique, and the common trap is assuming physical cabling is at fault when the real problem is broadcast-domain interference from the fax machine's traffic.

When a fax machine connected to a switch causes intermittent connectivity issues, configuring a dedicated VLAN isolates its traffic and prevents broadcast interference. This solution is strongly supported by community consensus, with 88 votes for VLAN configuration.

Common mistake: The most common wrong answer is A, 'Run a new Cat 5 line.' This is incorrect because the issue correlates specifically with fax machine usage, not with a physical cable fault; replacing the cable does not address the underlying traffic isolation problem.

Expert Analysis

Why the Answer Is Correct

Configuring a VLAN (Option D) is the correct first step because the fax machine's traffic is disrupting other devices on the same broadcast domain. When a fax machine sends large or broadcast-heavy traffic (especially if it has an IP-based fax function), it can flood the network segment, causing intermittent connectivity for other users. Placing the fax machine on its own VLAN separates its broadcast traffic from the rest of the network, eliminating the interference. As community comment [1] notes, isolating the fax machine 'can help prevent it from interfering with regular network traffic.' Comment [3] also reinforces that a dedicated VLAN 'directly addresses the correlation between fax usage and network disruption.'

Why the Other Options Are Wrong

Option A (Run a new Cat 5 line) is unnecessary because there is no evidence of a physical cable fault; the issue is traffic-related, not signal-related. Option B (Enable 802.1Q tagging) only enables trunking between switches or VLAN-tagged interfaces; it does not isolate the fax machine by itself and requires a VLAN to be configured first. Option C (Change the MTU) would only help if there were packet fragmentation problems, but the symptoms are caused by interference in the broadcast domain, not by MTU mismatches. Therefore, VLAN configuration is the only option that directly solves the stated problem.

Community Comment Notes

Community comments overwhelmingly support D, with several explanations pointing to traffic isolation. Comment [2] correctly states that the fax machine's traffic 'could be causing interference or broadcast issues that disrupt other devices on the same network' and that a VLAN 'isolates the traffic.' Comment [4] suggests A, but this lacks the logical connection to fax-machine usage as the trigger. The most useful comments highlight that the key is separating the fax machine's traffic from the rest of the network, which is exactly what a VLAN accomplishes.

Official Reference

These links open the official vendor documentation in a new tab.

Exam Strategy

On exam questions about intermittent issues tied to a specific device, look for options that segment or isolate that device's traffic. VLANs are a common answer when the symptoms point to broadcast storms or traffic interference, so think about broadcast domains before assuming cabling or MTU issues.

Community Votes

100%

100% of anonymous learners picked answer D. Votes are pick records left by other test-takers — they are not the verified answer.

Discussion 5 contributions

Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.

From public community threads 5

HeatSquad77 👍 4 Answered D

D. Configure a VLAN. Explanation: The issue described suggests that the fax machine, which is likely generating a high amount of traffic or interference, is causing disruption to other devices on the same network segment. In this case, placing the fax machine on a separate VLAN can help isolate it from other devices and prevent it from interfering with regular network traffic.
jmcd2 👍 2 Answered D

D Configure a VLAN The fax machine's network traffic could be causing interference or broadcast issues that disrupt other devices on the same network. By configuring a VLAN (Virtual Local Area Network), the engineer can isolate the traffic from the fax machine onto its own separate network segment, preventing it from affecting other devices.
escomgmt 👍 1

A. Run a new Cat 5 line, Intermittent connection issues when a fax machine (often analog and potentially connected through a VoIP adapter or similar setup) is in use suggest possible interference or crosstalk on the current cable. Running a new, dedicated Cat 5 line for the fax machine would isolate it from the rest of the network traffic on the switch, reducing interference and connection problems. This is a straightforward approach to eliminate potential issues with shared cabling or interference.
ec_ 👍 1 Answered D

Isolating the fax machine into a dedicated VLAN is the most effective first step to mitigate interference and stabilize the network. This approach directly addresses the correlation between fax usage and network disruption.
SuntzuLegacy 👍 1 Answered A

A run a new Cat 5 Line is correct.

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