Nokia: OSPF MTU mismatch

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

What this guide covers

Diagnose and fix OSPF MTU mismatch on a Nokia device (SR OS / SR Linux).

Most likely cause + fix

Both routers must have identical MTU on the OSPF interface. Match them explicitly.

Diagnostic CLI

show port
# Use the SR OS / SR Linux equivalents of:
#   show ip route / show route
#   show ip bgp summary / show bgp summary
#   show ip ospf neighbor / show ospf neighbor
#   show log | include BGP|OSPF

When the issue persists

• Capture admin tech-support and open a Nokia Customer Care case.
• Cross-reference https://customer.nokia.com for known issues in your release.

Frequently asked questions

Will this work on my specific SR OS / SR Linux version?

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

Should I open a Nokia Customer Care 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 Nokia official documentation?

https://documentation.nokia.com, 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 Nokia fix guides → /nokia/
• All vendor guides → /vendors/

Related fixes

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

• Nokia: OSPF duplicate router-id
• Nokia: OSPF neighbor stuck ExStart
• Best Nokia router for branch office
• Best Nokia router for enterprise data centre
• Best Nokia router for retail store
• Best Nokia router for SD-WAN deployment

References

• Nokia support portal: https://customer.nokia.com
• Nokia knowledge base: https://documentation.nokia.com
• Nokia security advisories: https://www.nokia.com/about-us/security/vulnerability-management/
• Open a case: https://customer.nokia.com

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

What changed recently?

Fault diagnosis on a Nokia: device goes faster when you map the symptom to a recent change:

• Did firmware update in the last 7 days?
• Did the network (router, ISP, VPN) change?
• Was the device moved physically?
• Did paired devices (phone, hub, app) update?
• Were any accessories swapped in or out?

The answer narrows the root cause to a manageable subset.

Before you start

A few things to confirm so the Nokia: 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.

Verification checklist

After applying the fix on your Nokia: device, confirm:

• The original symptom is no longer reproducible.
• Related features (status LEDs, app sync, paired accessories) still work.
• The device responds to a soft reboot without the fault returning.
• Any error codes that were on display have cleared.
• Documentation (your service log, the brand companion app) reflects the change.

When to call Nokia: 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

Is it safe to apply during business hours?

If the device is in production use, apply during a scheduled maintenance window. Most procedures need 2-15 minutes of downtime. Capture pre-change state so you can roll back if needed.

How long does this fix usually take?

Most users complete the steps in 20-45 minutes the first time, and 5-10 minutes on subsequent runs once the menu paths are familiar.

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).