HowToFixMe
IP / Network Issue

Arista router: ARP poisoning / spoofing detected

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

⚡ At a glance
VendorArista
Operating systemArista EOS
CategoryIP / Network Issue
Skill levelIntermediate to advanced
DIY-able?Yes with CLI access; some scenarios need Arista TAC + RMA.

What this guide covers

Real-world context. Cost envelope: ~Rs 0 INR under Arista A-Care, otherwise ~Rs 10,000 to Rs 1,50,000 INR for replacement units (around $120 to $1,800 USD). Time at the keyboard: ~20 to 60 minutes triage. Time end-to-end including verification: ~1 to 4 hours including a failback test. Have the switch serial, a startup-config backup, and console access staged before the first command so you do not stall on missing inputs.

Fix ARP poisoning / spoofing detected on a Arista router.

Full fix path

  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 interfaces status
show interfaces Ethernet1 detail
show inventory

When the issue persists

Frequently asked questions

Will this work on my specific Arista EOS version?

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

Should I open a Arista TAC 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 Arista official documentation?

https://www.arista.com/en/support/toi: 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.

References

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

Why this matters for your day-to-day

A Arista device that's misbehaving costs more than the fix itself: lost productivity, missed calls, security risk, even safety risk in some categories. Treating the symptom quickly with a documented procedure is cheaper than letting it persist. The steps above are written to get you back to working in under an hour where possible, and to flag clearly when escalation is the right call.

Quick triage

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

Confirm it stuck

After applying the fix on your Arista device, confirm:

When to call Arista support instead

Escalate if:

More frequently asked questions

Will this void my warranty?

Applying official firmware updates and following the user manual will not affect warranty. Opening sealed components, jumping safety circuits, or using third-party parts can void warranty in most jurisdictions.

Does this affect other devices on my network?

Generally no. The procedure is local to this device. Network-side changes (firmware updates that affect TLS, SMB, or routing) are flagged explicitly in the steps.

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.

What if my model isn't exactly the same revision?

Cross-check the model code on the rating plate against the manufacturer support page. Major firmware generations sometimes shift the menu path; the option is usually under a similarly-named section.

Field notes from real incidents on Arista

When I work on Arista router: ARP poisoning / spoofing detected the rhythm I lean on is the one I have built over years of these tickets. EOS-API (eAPI) over HTTPS is the cleanest way to script Arista at scale; do not wrap CLI screen-scraping when eAPI returns JSON. Arista EOS lets you reload a module without reloading the chassis on most platforms, I use that capability more than people realise. CloudVision Portal alerts are noisy unless you tune them; I disable the defaults and re-enable the ones that map to actual production events.

Tools I actually reach for

For Arista router: ARP poisoning / spoofing detected on Arista the cheapest signal I can land usually comes from a known order of operations, not a kitchen-sink approach. I start with show platform hardware capacity because it is the lowest-friction way to confirm the failure is real and reproducible. If that returns ambiguous data, I escalate to show tech-support (capture for TAC), show running-config | include <feature>, ping vrf <vrf> <target>, and finally to traceroute vrf <vrf> <target> only when the cheaper tools cannot reach the layer the failure lives in. That ordering matches the failure surfaces I have actually seen on Arista units over the last few years, not an abstract taxonomy. The cheap signals gate the expensive ones so the investigation does not balloon into a multi-hour exercise.

Verification I run before I close the ticket

Before I mark Arista router: ARP poisoning / spoofing detected resolved on a Arista unit, the verification loop below is what I actually run. Each step proves a different layer is green, and the order matters - the cheap checks gate the more expensive ones so I never burn an hour on a deep test that a shallow one would have failed in seconds.

show bgp summary  # confirm session state after route changes

If that one comes back clean, move to the next check. If it does not, stop and dig in there before layering more verification on top of a red signal.

show interfaces <int> | include errors|drops|CRC

If that one comes back clean, move to the next check. If it does not, stop and dig in there before layering more verification on top of a red signal.

show spanning-tree summary  # confirm topology stability

Only when every line above runs clean do I close the ticket and update the runbook with the timestamps. A green verification that nobody can reproduce is not a fix, it is luck waiting to regress.

Where I check first when the docs disagree

When two sources contradict each other on a Arista detail, the disambiguation order I lean on is stable across products and across years. eos.arista.com for the official software documentation is where I start for the ground-truth view. arista.com/en/support/product-documentation for EOS command references is where I start for the ground-truth view. github.com/aristanetworks for open-source tooling like Ansible roles is where I start for the ground-truth view. Random blog posts and reseller wikis are signal, not ground truth, and I treat them as such until the references above either confirm or contradict the claim. The cost of trusting an unauthoritative source on Arista router: ARP poisoning / spoofing detected is rarely worth the time it saved.

Pitfalls I have walked into on this exact path

The shortcuts that look smart on Arista router: ARP poisoning / spoofing detected have a habit of biting back. The pitfalls below are the ones I have personally walked into on a Arista unit, not things I read about. CloudVision Portal alerts are noisy unless you tune them; I disable the defaults and re-enable the ones that map to actual production events. EOS-API (eAPI) over HTTPS is the cleanest way to script Arista at scale; do not wrap CLI screen-scraping when eAPI returns JSON. Show tech-support detail is the artifact Arista TAC expects on call one; bundle it with the agent logs before you open the ticket. When in doubt I revert to the slower path that the manual prescribes - the time I save by skipping it is always smaller than the time I spend cleaning up afterwards.

What I tell the next on-call

When I hand Arista router: ARP poisoning / spoofing detected off to the next person on rotation, the three lines I leave in the runbook are these. First, the symptom signature on Arista - not a paraphrase, the exact string that surfaces in logs or on the screen. Second, the diagnostic that gave the highest signal in the least time. Third, the exact verification command whose green output justified closing the ticket. That trio is what turns a one-off fix into a runbook entry the next engineer can use without paging me at three in the morning.

I also add a one-line note on the cost of getting this wrong. For Arista router: ARP poisoning / spoofing detected on a Arista unit, the cost is rarely the replacement part or the patch itself. It is the downtime, the second site visit, and the trust deficit you spend with whoever owns the asset when the fix does not hold. That framing keeps the next on-call from choosing the cheap-looking shortcut that ends up costing the most in elapsed hours and goodwill.

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

People also ask

Will this work on my specific Arista EOS version?

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

Should I open a Arista TAC 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 Arista official documentation?

https://www.arista.com/en/support/toi, 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.