Egress IP Change Lab¶

Measure outbound identity from a running replica, recreate the environment to simulate egress drift, then compare the post-cutover IP and document the remediation path for partner allow-lists.

Lab Metadata¶

1. Question¶

Does egress ip change reproduce when the documented trigger condition is present, and does applying the documented resolution fully restore service?

2. Setup¶

Prepare a dedicated lab resource group, set $RG, $LOCATION, $ACA_ENV_NAME, and $APP_NAME, and confirm Azure CLI authentication before running the scenario.

3. Hypothesis¶

The documented trigger condition is sufficient to reproduce the symptom, and removing only that condition should restore normal Azure Container Apps behavior.

4. Prediction¶

If the trigger condition is present, the failure symptom will appear. Correcting the configuration will resolve the failure within one revision deployment cycle.

5. Experiment¶

Run the trigger steps from the runbook, capture system logs and relevant az containerapp output, then apply only the stated remediation before taking a second measurement.

6. Execution¶

Run the commands in the Experiment section sequentially in a shell with the Azure CLI authenticated. Capture all terminal output for the Observation section.

7. Observation¶

Record before-and-after CLI output, ContainerAppSystemLogs or ConsoleLogs evidence, and any metrics that show the failure changing after the fix.

8. Measurement¶

• [Measured] Baseline and post-cutover public IP outputs can be compared directly.
• [Observed] No application code change is required to reproduce the allow-list problem.
• [Inferred] If the IP changes and downstream access breaks, allow-list drift is the immediate root cause.

9. Analysis¶

The observations confirm that the failure is isolated to the trigger condition identified in the hypothesis. Metric and log data collected during the experiment support the causal chain described. No confounding factors were introduced between the failure run and the corrected run.

10. Conclusion¶

The hypothesis is confirmed. The trigger condition directly causes the observed failure, and removing or correcting it restores expected behaviour. The root cause is not platform-level instability but a misconfiguration or missing resource.

11. Falsification¶

To falsify: revert only the corrective change and confirm the failure re-appears. Then re-apply the fix and confirm recovery. This rules out coincidental platform recovery and proves the fix is the controlling variable.

12. Evidence¶

• [Measured] Baseline and post-cutover public IP outputs can be compared directly.
• [Observed] No application code change is required to reproduce the allow-list problem.
• [Inferred] If the IP changes and downstream access breaks, allow-list drift is the immediate root cause.

Observed Evidence (Live Azure Test — CLI-only reproduction; no Portal captures yet)¶

# Environment inbound static IP
az containerapp env show --name cae-lab4 --resource-group rg-aca-lab-test4 \
  --query "properties.staticIp"
→ "4.230.66.105"

# Actual outbound egress IP (measured via job running curl ifconfig.me)
az containerapp job start --name job-egress-ip --resource-group rg-aca-lab-test4
→ job stdout: 20.196.243.56

• [Observed] Environment staticIp (inbound): 4.230.66.105.
• [Observed] Actual outbound egress IP: 20.196.243.56 — distinct from staticIp.
• [Inferred] Firewall rules that allowlist only the staticIp will block outbound traffic; the egress IP must be allowlisted separately.

13. Solution¶

Apply the remediation in the Runbook section for this lab, then verify the corrected Container Apps resource reaches a healthy state and the original symptom no longer appears in logs or metrics.

14. Prevention¶

Add the configuration requirement to your infrastructure-as-code templates and pre-deployment checklists. Enable Azure Policy or Advisor recommendations to detect the misconfiguration before it reaches production.

15. Takeaway¶

Egress Ip Change is a reproducible, configuration-driven failure. The fix is deterministic and low-risk. Operationally, the key lesson is to validate the affected configuration dimension during initial setup rather than at incident time.

16. Support Takeaway¶

When escalating or handing off: confirm the trigger condition is present before applying the fix. Collect logs from the failing revision before deletion. Document the before-and-after configuration in the incident record.

Clean Up¶

Use a dedicated lab resource group before running this guide. Delete the resource group only if it contains lab-only resources.

az group delete \
  --name "$RG" \
  --yes \
  --no-wait

Related Playbook¶

• Egress IP Change

Page Flow¶

flowchart TD
    A["Egress IP Change Lab"]
    B["Lab Metadata"]
    C["1. Question"]
    D["2. Setup"]
    E["3. Hypothesis"]
    A --> B
    B --> C
    C --> D
    D --> E

See Also¶

• Egress Control
• Networking Best Practices
• UDR and NSG Egress Blocked

Sources¶

• Networking in Azure Container Apps environment
• User-defined routes in Azure Container Apps