IBM AIX 7.1 – Common Problem 236 – 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

App connections fail with EADDRNOTAVAIL and netstat -an shows many TIME_WAIT.

Environment & Reproduction

Hit by high-throughput services that open many short-lived outbound TCP connections.

Root Cause Analysis

AIX ephemeral range is too narrow or tcp_finwait2 too long for the connection rate.

Quick Triage

Run netstat -an | awk ‘{print $6}’ | sort | uniq -c to count states.

Step-by-Step Diagnosis

Use no -a | grep -E ‘tcp_ephemeral|tcp_finwait2’ to read current tunables.

Solution – Primary Fix

Widen ports with no -p -o tcp_ephemeral_low=10000 -o tcp_ephemeral_high=65535.

Solution – Alternative Approaches

Reduce tcp_finwait2 via no -p -o tcp_finwait2=15 and enable tcp_tcpsecure as needed.

Verification & Acceptance Criteria

Apps no longer hit EADDRNOTAVAIL and TIME_WAIT counts stay bounded.

Rollback Plan

Revert with no -p -d tcp_ephemeral_low to restore previous defaults.

Prevention & Hardening

Reuse client connections (HTTP keep-alive, JDBC pools) and monitor with netstat.

Related Errors & Cross-Refs

Related to client retry storms, NFS mount churn, and LDAP/HTTP timeouts.

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 no command and TCP tuning reference.