IBM AIX 7.3 – Common Problem 005 – 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

EtherChannel ent4 reports link flapping and applications experience TCP resets.

Environment & Reproduction

IBM AIX 7.3 LPAR exhibiting network adapter / EtherChannel issues under standard PowerVM workloads.

lsdev -Cc adapter
entstat -d ent4

Root Cause Analysis

Switch port misconfiguration or adapter firmware bug causes failover to backup interface.

Quick Triage

Confirm scope with errpt, recent changes, and subsystem state via lssrc.

entstat -d ent4 | head -40
netstat -in

Step-by-Step Diagnosis

Examine entstat for adapter errors and verify backup adapter status.

entstat -d ent4
lsattr -El ent4

Solution – Primary Fix

Reset the EtherChannel and re-attach with correct hash_src_dst mode.

/usr/lib/methods/ethchan_config -d ent4 ent0
/usr/lib/methods/ethchan_config ent4 ent0,ent1

Solution – Alternative Approaches

Replace with VIOS SEA failover if backed by Virtual I/O Server.

Verification & Acceptance Criteria

Confirm subsystem returns to RUNNING state and errpt shows no new entries.

netstat -i
entstat ent4

Rollback Plan

Restore prior configuration from mksysb or alt_disk_install clone if the fix regresses.

rmdev -dl ent4 && mkdev -l ent4

Prevention & Hardening

Encode the fix in NIM customisation scripts and monitor via topas/nmon.

no -p -o tcp_pmtu_discover=1

Related Errors & Cross-Refs

errpt LABEL=GOENT_LINK_DOWN; SEA failover events

Related tutorial: View the step-by-step tutorial for aix-7.3.

View all aix-7.3 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

AIX EtherChannel and IEEE 802.3ad reference