SonicWall firewall: ARP poisoning / spoofing detected

By Sai Kiran Pandrala · reviewed by Sai Kiran Pandrala, Editor Last verified: 2026-05-30

What this guide covers

Fix ARP poisoning / spoofing detected on a SonicWall firewall.

Step-by-step

1. Identify the offending source MAC via debug or capture.
2. Enable DHCP snooping + Dynamic ARP Inspection on access VLANs.
3. Mark uplinks as trusted; untrusted ports rate-limit + validate.
4. Monitor inspection statistics for repeat attacks.

CLI / commands

show interface
show interface X0
show status

When the issue persists

• Open a SonicWall Support case with the tech-support bundle.
• Provide the timeline + recent changes.

Frequently asked questions

Will this work on my specific SonicOS version?

The procedure reflects current SonicOS behaviour. Older releases may need minor syntax adjustments, use the CLI help (? or tab-completion) to verify.

Should I open a SonicWall Support case immediately?

Open one if you suspect hardware failure or the symptom persists after a maintenance-window reload. Make sure your support entitlement is active first.

Where can I find the SonicWall official documentation?

https://www.sonicwall.com/support/knowledge-base/: search the product family + feature name.

Is this procedure safe in production?

Test in a lab or maintenance window first. Capture pre-change state so you can roll back.

Related guides

• All SonicWall fix guides → /sonicwall/
• All vendor guides → /vendors/

Related fixes

Related guides worth a look while you sort this one out:

• SonicWall switch: ARP poisoning / spoofing detected
• SonicWall firewall: asymmetric routing detected
• SonicWall firewall: duplicate IP address detected
• Best SonicWall firewall for branch office
• Best SonicWall firewall for enterprise data centre
• Best SonicWall firewall for retail store

References

• SonicWall support portal: https://www.sonicwall.com/support
• SonicWall knowledge base: https://www.sonicwall.com/support/knowledge-base/
• SonicWall security advisories: https://psirt.global.sonicwall.com
• Open a case: https://www.mysonicwall.com

Reference material, not professional advice. Validate against your specific SonicOS version and test in a non-production environment before applying.

Common patterns we see

When this symptom shows up on a SonicWall device, three patterns repeat:

1. Recent firmware update changed behavior, the symptom started within a week of an OTA push. Rollback or wait for the hotfix. 2. Environmental trigger. temperature, humidity, line voltage, network changes. Look at what changed in the environment. 3. Cumulative wear, components like batteries, gaskets, fans degrade over time. Replace the consumable rather than chasing a software fix.

Knowing which pattern applies saves time on the wrong fix.

Before you start

A few things to confirm so the SonicWall device fix goes cleanly:

• Latest firmware downloaded if you're going to update.
• Warranty + support contract status checked: opening sealed parts may void it.
• Backup of current configuration (where applicable) taken.
• Spare parts on hand if you anticipate replacement.
• Adequate workspace, lighting, and time, rushing causes regressions.

How to confirm it's actually fixed

On a SonicWall device, the test is rarely "reboot and see". Use this list:

• Active reproduction: trigger the original failure path on purpose.
• Indirect reproduction: do an activity that would expose the same subsystem.
• Status indicator review: every LED / display / app status should be green.
• 24-hour soak: leave the device under normal load overnight; check the next morning.
• Telemetry check: review the device or app's diagnostic log for new error entries.

Escalation guide

For a SonicWall device, the right escalation depends on impact:

• Cosmetic / minor: log a ticket via the SonicWall app or web portal. Response 1-3 business days.
• Mid-impact: phone support. Have your serial number ready.
• Critical (production down, safety issue): in-person dealer / TAC visit. Bring proof of purchase.
• Out of warranty: third-party repair shop with manufacturer-certified technicians.

More frequently asked questions

Will the procedure work on the international variant?

Some features and firmware paths are region-locked. Check the model spec sheet to confirm your variant supports the menu option referenced. If you're outside the US/EU, look for the regional support portal.

Can I roll this back if something breaks?

Yes for software-level changes (firmware rollback, config rollback). Hardware changes are usually one-way. Always back up settings before starting.

Are there safer alternatives for non-technical users?

Yes. the manufacturer's self-service troubleshooter (HP Smart, LG ThinQ, Samsung Members, similar) usually walks through the same steps in a guided UI. Use that first if you're not comfortable with menu paths.

Should I update firmware first or last?

Update firmware first if a release note specifically mentions your symptom. Otherwise, finish the troubleshooting flow first, then update; that way you can isolate whether the update or the underlying fix solved it.

What if the fix returns after a reboot?

Persistent fault returns mean either: a hardware fault (escalate), a configuration that's being overwritten by a sync source (check cloud profiles), or a regression in a recent firmware update (rollback).