IBM AIX 7.1 – Common Problem 235 – Diagnosis and Fix

📖 ~1 min read

Table of contents

1. Symptom & Impact
2. Environment & Reproduction
3. Root Cause Analysis
4. Quick Triage
5. Step-by-Step Diagnosis
6. Solution – Primary Fix
7. Solution – Alternative Approaches
8. Verification & Acceptance Criteria
9. Rollback Plan
10. Prevention & Hardening
11. Related Errors & Cross-Refs
12. References & Further Reading

Symptom & Impact

enX repeatedly reports LINK UP/DOWN in errpt and TCP sessions reset.

Environment & Reproduction

Triggered by bad cable, SFP, switch port misconfig, or EtherChannel partner mismatch.

Root Cause Analysis

AIX en device toggles state because the underlying ent has unstable link or duplex.

Quick Triage

Run entstat -d entN and netstat -i to spot Ierrs, Oerrs, and flapping counters.

Step-by-Step Diagnosis

Inspect errpt -aj GOENT_LINK_DOWN and switch port logs for matching events.

Solution – Primary Fix

Replace cable or SFP, then run chdev -l entN -a media_speed=Auto_Negotiation.

Solution – Alternative Approaches

For EtherChannel, recreate with mkdev/chdev and align mode with the switch (LACP vs static).

Verification & Acceptance Criteria

entstat -d shows stable Link Status=Up and netstat -i Ierrs do not grow.

Rollback Plan

Roll back EtherChannel changes with rmdev/chdev to the previous mode setting.

Prevention & Hardening

Lock duplex/speed on critical links and monitor entstat with cron snapshots.

Related Errors & Cross-Refs

Related to TCP retransmits, NFS hangs, and EtherChannel failover events.

Related tutorial: View the step-by-step tutorial for aix-7.1.

View all aix-7.1 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

IBM AIX 7.2 entstat, EtherChannel, and network tuning documentation.