Define source and destination
Start by defining exactly what is failing, which server is affected and whether the problem affects one client or multiple systems.
Check NSG association
Check the local configuration that controls the operation. Compare it with a known-good server or client where possible.
Review rule priority
Run a direct test for the dependency. Capture the exact result so you can distinguish configuration, connectivity and application failures.
Use effective security rules
Review the relevant server-side configuration and logs. Look for timestamps that match the reported failure.
Check routes
Validate security, permissions and service state before changing production configuration.
Validate the application port
After the fix, repeat the original test and document the working configuration so the procedure can be reused.
Useful commands
Run these checks from an elevated PowerShell session where appropriate. Replace example names with your environment.
Effective NSG
az network nic list-effective-nsg -g RG01 -n VM01NICNSG rules
az network nsg rule list -g RG01 --nsg-name NSG01 -o tableQuick troubleshooting path
Use this sequence to isolate the failing dependency before changing production configuration.
What good troubleshooting looks like
Good infrastructure troubleshooting is evidence-driven. Capture the original state, test the dependency that can prove or disprove your hypothesis, make the smallest safe change and repeat the original test.
Symptom → hypothesis → direct test → result → controlled change → validation → documentation
Frequently asked questions
What should I check first?
Start with the exact symptom and validate the dependency closest to the failure, such as DNS, a port, a service, storage or an authentication path.
Should I change production configuration immediately?
No. Capture the current state first, test the suspected dependency and make one controlled change at a time.
How should I document the fix?
Record the symptom, commands used, result, configuration change and validation result so the procedure can be repeated.
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