Nvidia (Mellanox) Switch Port stuck disabled by UDLD: How to Fix

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

What this guide covers

Resolve a Nvidia (Mellanox) switch port UDLD.

Cause + fix

Unidirectional link detected, usually a fibre cable or SFP fault. Replace one end.

CLI / commands

nv show interface
nv show interface swp1

# Apply the fix above, then bounce the port:
nv config (NVUE)
# (interface shutdown / no shutdown: vendor-specific)
nv config save

Avoid recurrence

• Identify and remove the source of the violation (BPDU, MAC, storm).
• Tune the protection threshold if it's too aggressive for normal traffic.
• Add monitoring for repeat events.

Frequently asked questions

Will this work on my specific Cumulus Linux / NVOS / SONiC version?

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

Should I open a Nvidia Enterprise 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 Nvidia (Mellanox) official documentation?

https://docs.nvidia.com/networking/. 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 Nvidia (Mellanox) fix guides → /nvidia/
• All vendor guides → /vendors/

Related fixes

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

• Nvidia (Mellanox) Switch Port stuck disabled by BPDU guard: How to Fix
• Nvidia (Mellanox) Switch Port stuck disabled by link-flap: How to Fix
• Nvidia (Mellanox) Switch Port stuck disabled by loop detection: How to Fix
• Nvidia (Mellanox) Switch Port stuck disabled by PoE budget exceeded: How to Fix
• Nvidia (Mellanox) Switch Port stuck disabled by port security violation: How to Fix
• Nvidia (Mellanox) Switch Port stuck disabled by storm-control: How to Fix

References

• Nvidia (Mellanox) support portal: https://enterprise-support.nvidia.com/
• Nvidia (Mellanox) knowledge base: https://docs.nvidia.com/networking/
• Nvidia (Mellanox) security advisories: https://www.nvidia.com/en-us/security/
• Open a case: https://enterprise-support.nvidia.com/s/createcase

Reference material, not professional advice. Validate against your specific Cumulus Linux / NVOS / SONiC version and test in a non-production environment before applying.

Why this matters for your day-to-day

A Nvidia 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.

Before you start

A few things to confirm so the Nvidia 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.

Quick verification

Before you walk away from a Nvidia device fix, run through:

1. Reproduce the original trigger, does the issue reappear? 2. Check the device's status / health screen for any new alerts. 3. Confirm paired devices (app, hub, controller) reconnected. 4. Save / commit any configuration changes per the device's normal workflow. 5. Note the change in your maintenance log with date + firmware version.

When to call Nvidia support instead

Escalate if:

• The same symptom returns within 24 hours of a clean fix.
• You see physical damage (burn marks, swollen battery, cracked PCB).
• The device is in warranty and a hardware replacement is the cheaper outcome.
• Repair requires specialised tools you don't own (alignment jigs, calibration software).
• Following the official path keeps the warranty intact, which matters more than the time spent.

More frequently asked questions

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.

Why is this happening on a brand-new unit?

Out-of-box defects do occur. If you've owned the device under 30 days and the symptom persists after a factory reset, escalate to the seller for replacement under DOA terms before opening a manufacturer support case.

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.

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).

How often should I run preventive checks?

Quarterly for most consumer devices; monthly for production / commercial devices. Set a calendar reminder so the device stays healthy between issues.