Introduction

NAT gateway SNAT ports exhausted after migration when connection count high. This guide provides step-by-step diagnosis and resolution.

Symptoms

Typical error output:

bash
Error: Migration operation failed
Check migration logs for details
Verify source and target configuration

Common Causes

  1. 1.Insufficient network bandwidth for data transfer
  2. 2.Configuration mismatch between source and target
  3. 3.Timeout values too short for data volume
  4. 4.Dependencies not properly sequenced

Step-by-Step Fix

Step 1: Check Current State

bash
# Check migration status
cat /var/log/migration/status.log
# Verify target connectivity
ping target-server
curl -I https://target-endpoint/health

Step 2: Identify Root Cause

bash
# Check migration logs
tail -f /var/log/migration/migration.log
# Verify source state
ssh source-server "systemctl status application"
# Check target state
ssh target-server "df -h && free -m"

Step 3: Apply Primary Fix

```bash # Primary fix: Verify and reconfigure migration # Check current status migration-tool status --verbose

# Adjust parameters migration-tool config --bandwidth 1Gbps --timeout 8h

# Resume migration migration-tool resume --verify-integrity ```

Step 4: Apply Alternative Fix

```bash # Alternative: Manual verification # Check data consistency rsync -avz --dry-run source/ target/

# Verify network throughput iperf3 -c target-server

# Check logs grep -i error /var/log/migration/*.log ```

Step 5: Verify the Fix

bash
# Verify migration completed
migration-tool verify --source <source> --target <target>
# Run smoke tests
./scripts/smoke-test.sh target-endpoint
# All checks should pass

Common Pitfalls

  • Not testing migration with production-like data volume
  • Insufficient network bandwidth allocation
  • Forgetting to update DNS TTL before cutover
  • Not running data validation after migration

Best Practices

  • Create detailed migration runbook
  • Test migration multiple times in staging
  • Have rollback plan ready
  • Monitor closely during and after migration
  • Migration Data Loss
  • Migration Performance Issues
  • Migration Rollback Failed
  • Post-Migration Issues